Yocto Project Reference Manual Ref

Yocto_Ref-Manual

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Richard Purdie, Linux Foundation


by Richard Purdie
Copyright © 2010-2014 Linux Foundation
Permission is granted to copy, distribute and/or modify this document under the terms of the Creative Commons
Attribution-Share Alike 2.0 UK: England & Wales [http://creativecommons.org/licenses/by-sa/2.0/uk/] as published
by Creative Commons.

Note
For the latest version of this manual associated with this Yocto Project release, see the Yocto Project
Reference Manual [http://www.yoctoproject.org/docs/1.8/ref-manual/ref-manual.html] from the Yocto
Project website.

Table of Contents
1. Introduction ........................................................................................................................... 1
1.1. Introduction ................................................................................................................ 1
1.2. Documentation Overview ............................................................................................ 1
1.3. System Requirements ................................................................................................. 2
1.3.1. Supported Linux Distributions ........................................................................... 2
1.3.2. Required Packages for the Host Development System ....................................... 3
1.3.3. Required Git, tar, and Python Versions .............................................................. 5
1.4. Obtaining the Yocto Project ......................................................................................... 6
1.5. Development Checkouts ............................................................................................. 7
2. Using the Yocto Project .......................................................................................................... 8
2.1. Running a Build .......................................................................................................... 8
2.1.1. Build Overview ................................................................................................. 8
2.1.2. Building an Image Using GPL Components ........................................................ 8
2.2. Installing and Using the Result .................................................................................... 8
2.3. Debugging Build Failures ............................................................................................. 9
2.3.1. Task Failures .................................................................................................... 9
2.3.2. Running Specific Tasks ..................................................................................... 9
2.3.3. Dependency Graphs ....................................................................................... 10
2.3.4. General BitBake Problems .............................................................................. 10
2.3.5. Development Host System Issues ................................................................... 10
2.3.6. Building with No Dependencies ...................................................................... 10
2.3.7. Variables ........................................................................................................ 11
2.3.8. Recipe Logging Mechanisms ........................................................................... 11
2.3.9. Other Tips ...................................................................................................... 12
2.4. Maintaining Build Output Quality ............................................................................... 12
2.4.1. Enabling and Disabling Build History ............................................................... 12
2.4.2. Understanding What the Build History Contains .............................................. 13
2.5. Speeding Up the Build .............................................................................................. 17
3. A Closer Look at the Yocto Project Development Environment ............................................... 19
3.1. User Configuration .................................................................................................... 20
3.2. Metadata, Machine Configuration, and Policy Configuration ........................................ 21
3.2.1. Distro Layer ................................................................................................... 23
3.2.2. BSP Layer ...................................................................................................... 23
3.2.3. Software Layer ............................................................................................... 23
3.3. Sources .................................................................................................................... 24
3.3.1. Upstream Project Releases ............................................................................. 25
3.3.2. Local Projects ................................................................................................. 25
3.3.3. Source Control Managers (Optional) ................................................................ 26
3.3.4. Source Mirror(s) ............................................................................................. 26
3.4. Package Feeds .......................................................................................................... 26
3.5. BitBake ..................................................................................................................... 27
3.5.1. Source Fetching ............................................................................................. 28
3.5.2. Patching ......................................................................................................... 29
3.5.3. Configuration and Compilation ........................................................................ 30
3.5.4. Package Splitting ........................................................................................... 31
3.5.5. Image Generation .......................................................................................... 33
3.5.6. SDK Generation ............................................................................................. 35
3.6. Images ..................................................................................................................... 36
3.7. Application Development SDK ................................................................................... 37
4. Technical Details .................................................................................................................. 39
4.1. Yocto Project Components ......................................................................................... 39
4.1.1. BitBake .......................................................................................................... 39
4.1.2. Metadata (Recipes) ........................................................................................ 40
4.1.3. Classes .......................................................................................................... 40
4.1.4. Configuration ................................................................................................. 40
4.2. Cross-Development Toolchain Generation .................................................................. 40
4.3. Shared State Cache .................................................................................................. 43
4.3.1. Overall Architecture ....................................................................................... 43
4.3.2. Checksums (Signatures) ................................................................................. 43
4.3.3. Shared State .................................................................................................. 45
4.3.4. Tips and Tricks ............................................................................................... 46

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4.4. x32 ...........................................................................................................................
4.4.1. Support ..........................................................................................................
4.4.2. Completing x32 ..............................................................................................
4.4.3. Using x32 Right Now ......................................................................................
4.5. Wayland ...................................................................................................................
4.5.1. Support ..........................................................................................................
4.5.2. Enabling Wayland in an Image .......................................................................
4.5.3. Running Weston .............................................................................................
4.6. Licenses ...................................................................................................................
4.6.1. Tracking License Changes ...............................................................................
4.6.2. Enabling Commercially Licensed Recipes ........................................................
5. Migrating to a Newer Yocto Project Release ..........................................................................
5.1. General Migration Considerations ..............................................................................
5.2. Moving to the Yocto Project 1.3 Release ....................................................................
5.2.1. Local Configuration ........................................................................................
5.2.2. Recipes ..........................................................................................................
5.2.3. Linux Kernel Naming ......................................................................................
5.3. Moving to the Yocto Project 1.4 Release ....................................................................
5.3.1. BitBake ..........................................................................................................
5.3.2. Build Behavior ...............................................................................................
5.3.3. Proxies and Fetching Source ...........................................................................
5.3.4. Custom Interfaces File (netbase change) .........................................................
5.3.5. Remote Debugging ........................................................................................
5.3.6. Variables ........................................................................................................
5.3.7. Target Package Management with RPM ...........................................................
5.3.8. Recipes Moved ...............................................................................................
5.3.9. Removals and Renames .................................................................................
5.4. Moving to the Yocto Project 1.5 Release ....................................................................
5.4.1. Host Dependency Changes .............................................................................
5.4.2. atom-pc Board Support Package (BSP) ............................................................
5.4.3. BitBake ..........................................................................................................
5.4.4. QA Warnings ..................................................................................................
5.4.5. Directory Layout Changes ..............................................................................
5.4.6. Shortened Git SRCREV Values ..........................................................................
5.4.7. IMAGE_FEATURES ............................................................................................
5.4.8. /run ..............................................................................................................
5.4.9. Removal of Package Manager Database Within Image Recipes .........................
5.4.10. Images Now Rebuild Only on Changes Instead of Every Time .........................
5.4.11. Task Recipes ................................................................................................
5.4.12. BusyBox .......................................................................................................
5.4.13. Automated Image Testing .............................................................................
5.4.14. Build History ................................................................................................
5.4.15. udev ............................................................................................................
5.4.16. Removed and Renamed Recipes ...................................................................
5.4.17. Other Changes .............................................................................................
5.5. Moving to the Yocto Project 1.6 Release ....................................................................
5.5.1. archiver Class ..............................................................................................
5.5.2. Packaging Changes ........................................................................................
5.5.3. BitBake ..........................................................................................................
5.5.4. Changes to Variables .....................................................................................
5.5.5. Directory Layout Changes ..............................................................................
5.5.6. Package Test (ptest) .......................................................................................
5.5.7. Build Changes ................................................................................................
5.5.8. qemu-native ..................................................................................................
5.5.9. core-image-basic .........................................................................................
5.5.10. Licensing ......................................................................................................
5.5.11. CFLAGS Options ............................................................................................
5.5.12. Custom Image Output Types .........................................................................
5.5.13. Tasks ............................................................................................................
5.5.14. update-alternative Provider ......................................................................
5.5.15. virtclass Overrides ....................................................................................
5.5.16. Removed and Renamed Recipes ...................................................................
5.5.17. Removed Classes .........................................................................................
5.5.18. Reference Board Support Packages (BSPs) ....................................................

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5.6. Moving to the Yocto Project 1.7 Release ....................................................................
5.6.1. Changes to Setting QEMU PACKAGECONFIG Options in local.conf ....................
5.6.2. Minimum Git version ......................................................................................
5.6.3. Autotools Class Changes ................................................................................
5.6.4. Binary Configuration Scripts Disabled .............................................................
5.6.5. eglibc 2.19 Replaced with glibc 2.20 ........................................................
5.6.6. Kernel Module Autoloading .............................................................................
5.6.7. QA Check Changes ........................................................................................
5.6.8. Removed Recipes ...........................................................................................
5.6.9. Miscellaneous Changes ..................................................................................
6. Source Directory Structure ...................................................................................................
6.1. Top-Level Core Components ......................................................................................
6.1.1. bitbake/ .......................................................................................................
6.1.2. build/ ...........................................................................................................
6.1.3. documentation/ ............................................................................................
6.1.4. meta/ ............................................................................................................
6.1.5. meta-yocto/ ..................................................................................................
6.1.6. meta-yocto-bsp/ ...........................................................................................
6.1.7. meta-selftest/ ............................................................................................
6.1.8. meta-skeleton/ ............................................................................................
6.1.9. scripts/ .......................................................................................................
6.1.10. oe-init-build-env .....................................................................................
6.1.11. oe-init-build-env-memres .........................................................................
6.1.12. LICENSE, README, and README.hardware ..................................................
6.2. The Build Directory - build/ .....................................................................................
6.2.1. build/buildhistory .....................................................................................
6.2.2. build/conf/local.conf ................................................................................
6.2.3. build/conf/bblayers.conf ...........................................................................
6.2.4. build/conf/sanity_info ..............................................................................
6.2.5. build/downloads/ .........................................................................................
6.2.6. build/sstate-cache/ ...................................................................................
6.2.7. build/tmp/ ....................................................................................................
6.2.8. build/tmp/buildstats/ ................................................................................
6.2.9. build/tmp/cache/ .........................................................................................
6.2.10. build/tmp/deploy/ .....................................................................................
6.2.11. build/tmp/deploy/deb/ ..............................................................................
6.2.12. build/tmp/deploy/rpm/ ..............................................................................
6.2.13. build/tmp/deploy/ipk/ ..............................................................................
6.2.14. build/tmp/deploy/licenses/ .....................................................................
6.2.15. build/tmp/deploy/images/ .........................................................................
6.2.16. build/tmp/deploy/sdk/ ..............................................................................
6.2.17. build/tmp/sstate-control/ .......................................................................
6.2.18. build/tmp/sysroots/ ..................................................................................
6.2.19. build/tmp/stamps/ .....................................................................................
6.2.20. build/tmp/log/ ..........................................................................................
6.2.21. build/tmp/work/ .........................................................................................
6.2.22. build/tmp/work-shared/ ............................................................................
6.3. The Metadata - meta/ ...............................................................................................
6.3.1. meta/classes/ ..............................................................................................
6.3.2. meta/conf/ ....................................................................................................
6.3.3. meta/conf/machine/ .....................................................................................
6.3.4. meta/conf/distro/ .......................................................................................
6.3.5. meta/conf/machine-sdk/ ..............................................................................
6.3.6. meta/files/ ..................................................................................................
6.3.7. meta/lib/ .....................................................................................................
6.3.8. meta/recipes-bsp/ .......................................................................................
6.3.9. meta/recipes-connectivity/ .......................................................................
6.3.10. meta/recipes-core/ ...................................................................................
6.3.11. meta/recipes-devtools/ ............................................................................
6.3.12. meta/recipes-extended/ ............................................................................
6.3.13. meta/recipes-gnome/ ..................................................................................
6.3.14. meta/recipes-graphics/ ............................................................................
6.3.15. meta/recipes-kernel/ ................................................................................
6.3.16. meta/recipes-lsb4/ ...................................................................................

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6.3.17. meta/recipes-multimedia/ .........................................................................
6.3.18. meta/recipes-qt/ .......................................................................................
6.3.19. meta/recipes-rt/ .......................................................................................
6.3.20. meta/recipes-sato/ ...................................................................................
6.3.21. meta/recipes-support/ ..............................................................................
6.3.22. meta/site/ ..................................................................................................
6.3.23. meta/recipes.txt .......................................................................................
7. Classes ................................................................................................................................
7.1. allarch.bbclass .....................................................................................................
7.2. archiver.bbclass ....................................................................................................
7.3. autotools.bbclass ..................................................................................................
7.4. autotools-brokensep.bbclass ................................................................................
7.5. base.bbclass ...........................................................................................................
7.6. bin_package.bbclass ..............................................................................................
7.7. binconfig.bbclass ..................................................................................................
7.8. binconfig-disabled.bbclass ..................................................................................
7.9. blacklist.bbclass ..................................................................................................
7.10. boot-directdisk.bbclass .....................................................................................
7.11. bootimg.bbclass ...................................................................................................
7.12. bugzilla.bbclass ..................................................................................................
7.13. buildhistory.bbclass ...........................................................................................
7.14. buildstats.bbclass ..............................................................................................
7.15. buildstats-summary.bbclass ................................................................................
7.16. ccache.bbclass .....................................................................................................
7.17. chrpath.bbclass ...................................................................................................
7.18. clutter.bbclass ...................................................................................................
7.19. cmake.bbclass .......................................................................................................
7.20. cml1.bbclass .........................................................................................................
7.21. compress_doc.bbclass ...........................................................................................
7.22. copyleft_compliance.bbclass ..............................................................................
7.23. copyleft_filter.bbclass .....................................................................................
7.24. core-image.bbclass ..............................................................................................
7.25. cpan.bbclass .........................................................................................................
7.26. cross.bbclass .......................................................................................................
7.27. cross-canadian.bbclass .......................................................................................
7.28. crosssdk.bbclass ..................................................................................................
7.29. debian.bbclass .....................................................................................................
7.30. deploy.bbclass .....................................................................................................
7.31. devshell.bbclass ..................................................................................................
7.32. distro_features_check.bbclass ..........................................................................
7.33. distrodata.bbclass ..............................................................................................
7.34. distutils.bbclass ................................................................................................
7.35. distutils3.bbclass ..............................................................................................
7.36. externalsrc.bbclass ............................................................................................
7.37. extrausers.bbclass ..............................................................................................
7.38. fontcache.bbclass ................................................................................................
7.39. gconf.bbclass .......................................................................................................
7.40. gettext.bbclass ...................................................................................................
7.41. gnome.bbclass .......................................................................................................
7.42. gnomebase.bbclass ................................................................................................
7.43. grub-efi.bbclass ..................................................................................................
7.44. gsettings.bbclass ................................................................................................
7.45. gtk-doc.bbclass ...................................................................................................
7.46. gtk-icon-cache.bbclass .......................................................................................
7.47. gtk-immodules-cache.bbclass ..............................................................................
7.48. gummiboot.bbclass ................................................................................................
7.49. gzipnative.bbclass ..............................................................................................
7.50. icecc.bbclass .......................................................................................................
7.51. image.bbclass .......................................................................................................
7.52. image_types.bbclass ............................................................................................
7.53. image_types_uboot.bbclass ..................................................................................
7.54. image-live.bbclass ..............................................................................................
7.55. image-mklibs.bbclass ...........................................................................................
7.56. image-prelink.bbclass .........................................................................................

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7.57. image-swab.bbclass .............................................................................................. 89
7.58. image-vmdk.bbclass .............................................................................................. 89
7.59. insane.bbclass ..................................................................................................... 89
7.60. insserv.bbclass ................................................................................................... 92
7.61. kernel.bbclass ..................................................................................................... 92
7.62. kernel-arch.bbclass ............................................................................................ 92
7.63. kernel-module-split.bbclass .............................................................................. 93
7.64. kernel-yocto.bbclass ........................................................................................... 93
7.65. lib_package.bbclass ............................................................................................ 93
7.66. license.bbclass ................................................................................................... 93
7.67. linux-kernel-base.bbclass .................................................................................. 93
7.68. logging.bbclass ................................................................................................... 93
7.69. meta.bbclass ......................................................................................................... 93
7.70. metadata_scm.bbclass ........................................................................................... 93
7.71. mime.bbclass ......................................................................................................... 93
7.72. mirrors.bbclass ................................................................................................... 93
7.73. module.bbclass ..................................................................................................... 94
7.74. module-base.bbclass ............................................................................................ 94
7.75. multilib*.bbclass ................................................................................................ 94
7.76. native.bbclass ..................................................................................................... 94
7.77. nativesdk.bbclass ................................................................................................ 94
7.78. oelint.bbclass ..................................................................................................... 95
7.79. own-mirrors.bbclass ............................................................................................ 95
7.80. package.bbclass ................................................................................................... 95
7.81. package_deb.bbclass ............................................................................................ 96
7.82. package_ipk.bbclass ............................................................................................ 96
7.83. package_rpm.bbclass ............................................................................................ 96
7.84. package_tar.bbclass ............................................................................................ 96
7.85. packagedata.bbclass ............................................................................................ 96
7.86. packagegroup.bbclass ........................................................................................... 97
7.87. packageinfo.bbclass ............................................................................................ 97
7.88. patch.bbclass ....................................................................................................... 97
7.89. perlnative.bbclass .............................................................................................. 97
7.90. pixbufcache.bbclass ............................................................................................ 97
7.91. pkgconfig.bbclass ................................................................................................ 97
7.92. populate_sdk.bbclass ........................................................................................... 97
7.93. populate_sdk_*.bbclass ....................................................................................... 97
7.94. prexport.bbclass .................................................................................................. 98
7.95. primport.bbclass .................................................................................................. 98
7.96. prserv.bbclass ..................................................................................................... 98
7.97. ptest.bbclass ....................................................................................................... 98
7.98. ptest-gnome.bbclass ............................................................................................ 99
7.99. python-dir.bbclass .............................................................................................. 99
7.100. pythonnative.bbclass ......................................................................................... 99
7.101. qemu.bbclass ....................................................................................................... 99
7.102. qmake*.bbclass ................................................................................................... 99
7.103. qt4*.bbclass ....................................................................................................... 99
7.104. relocatable.bbclass .......................................................................................... 99
7.105. report-error.bbclass ....................................................................................... 100
7.106. rm_work.bbclass ................................................................................................ 100
7.107. rootfs*.bbclass ................................................................................................ 100
7.108. sanity.bbclass .................................................................................................. 100
7.109. scons.bbclass ................................................................................................... 101
7.110. sdl.bbclass ....................................................................................................... 101
7.111. setuptools.bbclass .......................................................................................... 101
7.112. setuptools3.bbclass ......................................................................................... 101
7.113. sip.bbclass ....................................................................................................... 101
7.114. siteconfig.bbclass .......................................................................................... 101
7.115. siteinfo.bbclass .............................................................................................. 101
7.116. spdx.bbclass ..................................................................................................... 101
7.117. sstate.bbclass .................................................................................................. 102
7.118. staging.bbclass ................................................................................................ 102
7.119. syslinux.bbclass .............................................................................................. 102
7.120. systemd.bbclass ................................................................................................ 102

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7.121. terminal.bbclass ..............................................................................................
7.122. testimage.bbclass ............................................................................................
7.123. texinfo.bbclass ................................................................................................
7.124. tinderclient.bbclass .......................................................................................
7.125. toaster.bbclass ................................................................................................
7.126. toolchain-scripts.bbclass ..............................................................................
7.127. typecheck.bbclass ............................................................................................
7.128. uboot-config.bbclass .......................................................................................
7.129. uninative.bbclass ............................................................................................
7.130. update-alternatives.bbclass ..........................................................................
7.131. update-rc.d.bbclass .........................................................................................
7.132. useradd.bbclass ................................................................................................
7.133. useradd-staticids.bbclass ..............................................................................
7.134. utility-tasks.bbclass .....................................................................................
7.135. utils.bbclass ...................................................................................................
7.136. vala.bbclass .....................................................................................................
7.137. waf.bbclass .......................................................................................................
8. Tasks .................................................................................................................................
8.1. Normal Recipe Build Tasks .......................................................................................
8.1.1. do_build .....................................................................................................
8.1.2. do_compile ..................................................................................................
8.1.3. do_compile_ptest_base ..............................................................................
8.1.4. do_configure ..............................................................................................
8.1.5. do_configure_ptest_base ..........................................................................
8.1.6. do_deploy ...................................................................................................
8.1.7. do_fetch .....................................................................................................
8.1.8. do_install ..................................................................................................
8.1.9. do_install_ptest_base ..............................................................................
8.1.10. do_package ................................................................................................
8.1.11. do_package_qa ..........................................................................................
8.1.12. do_package_write_deb ..............................................................................
8.1.13. do_package_write_ipk ..............................................................................
8.1.14. do_package_write_rpm ..............................................................................
8.1.15. do_package_write_tar ..............................................................................
8.1.16. do_packagedata .........................................................................................
8.1.17. do_patch ...................................................................................................
8.1.18. do_populate_lic .......................................................................................
8.1.19. do_populate_sdk .......................................................................................
8.1.20. do_populate_sysroot ................................................................................
8.1.21. do_rm_work ................................................................................................
8.1.22. do_rm_work_all .........................................................................................
8.1.23. do_unpack ..................................................................................................
8.2. Manually Called Tasks .............................................................................................
8.2.1. do_checkuri ................................................................................................
8.2.2. do_checkuriall ..........................................................................................
8.2.3. do_clean .....................................................................................................
8.2.4. do_cleanall ................................................................................................
8.2.5. do_cleansstate ..........................................................................................
8.2.6. do_devshell ................................................................................................
8.2.7. do_fetchall ................................................................................................
8.2.8. do_listtasks ..............................................................................................
8.2.9. do_package_index .......................................................................................
8.3. Image-Related Tasks ...............................................................................................
8.3.1. do_bootimg ..................................................................................................
8.3.2. do_bundle_initramfs ..................................................................................
8.3.3. do_rootfs ...................................................................................................
8.3.4. do_testimage ..............................................................................................
8.3.5. do_testimage_auto .....................................................................................
8.3.6. do_vmdkimg ..................................................................................................
8.4. Kernel-Related Tasks ...............................................................................................
8.4.1. do_compile_kernelmodules .........................................................................
8.4.2. do_diffconfig ............................................................................................
8.4.3. do_kernel_checkout ...................................................................................
8.4.4. do_kernel_configcheck ..............................................................................

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8.4.5. do_kernel_configme ...................................................................................
8.4.6. do_kernel_link_vmlinux ............................................................................
8.4.7. do_menuconfig ............................................................................................
8.4.8. do_savedefconfig .......................................................................................
8.4.9. do_sizecheck ..............................................................................................
8.4.10. do_strip ...................................................................................................
8.4.11. do_uboot_mkimage .....................................................................................
8.4.12. do_validate_branches ..............................................................................
8.5. Miscellaneous Tasks ................................................................................................
8.5.1. do_generate_qt_config_file .....................................................................
8.5.2. do_spdx .......................................................................................................
9. QA Error and Warning Messages ........................................................................................
9.1. Introduction ............................................................................................................
9.2. Errors and Warnings ................................................................................................
9.3. Configuring and Disabling QA Checks ......................................................................
10. Images ............................................................................................................................
11. Features ..........................................................................................................................
11.1. Machine Features ..................................................................................................
11.2. Distro Features ......................................................................................................
11.3. Image Features .....................................................................................................
11.4. Feature Backfilling .................................................................................................
12. Variables Glossary ............................................................................................................
13. Variable Context ..............................................................................................................
13.1. Configuration ........................................................................................................
13.1.1. Distribution (Distro) ....................................................................................
13.1.2. Machine .....................................................................................................
13.1.3. Local ..........................................................................................................
13.2. Recipes .................................................................................................................
13.2.1. Required ....................................................................................................
13.2.2. Dependencies ............................................................................................
13.2.3. Paths ..........................................................................................................
13.2.4. Extra Build Information ...............................................................................
14. FAQ .................................................................................................................................
15. Contributing to the Yocto Project ......................................................................................
15.1. Introduction ..........................................................................................................
15.2. Tracking Bugs .......................................................................................................
15.3. Mailing lists ...........................................................................................................
15.4. Internet Relay Chat (IRC) .......................................................................................
15.5. Links .....................................................................................................................
15.6. Contributions ........................................................................................................

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Chapter 1. Introduction
1.1. Introduction
This manual provides reference information for the current release of the Yocto Project. The Yocto
Project is an open-source collaboration project focused on embedded Linux developers. Amongst
other things, the Yocto Project uses the OpenEmbedded build system, which is based on the Poky
project, to construct complete Linux images. You can find complete introductory and getting started
information on the Yocto Project by reading the Yocto Project Quick Start [http://www.yoctoproject.org/
docs/1.8/yocto-project-qs/yocto-project-qs.html]. For task-based information using the Yocto Project,
see the Yocto Project Development Manual [http://www.yoctoproject.org/docs/1.8/dev-manual/devmanual.html] and the Yocto Project Linux Kernel Development Manual [http://www.yoctoproject.org/
docs/1.8/kernel-dev/kernel-dev.html]. For Board Support Package (BSP) structure information, see
the Yocto Project Board Support Package (BSP) Developer's Guide [http://www.yoctoproject.org/
docs/1.8/bsp-guide/bsp-guide.html]. You can find information on tracing and profiling in the Yocto
Project Profiling and Tracing Manual [http://www.yoctoproject.org/docs/1.8/profile-manual/profilemanual.html#profile-manual]. For information on BitBake, which is the task execution tool the
OpenEmbedded build system is based on, see the BitBake User Manual [http://www.yoctoproject.org/
docs/1.8/bitbake-user-manual/bitbake-user-manual.html#bitbake-user-manual]. Finally, you can also
find lots of Yocto Project information on the Yocto Project website [http://www.yoctoproject.org].

1.2. Documentation Overview
This reference manual consists of the following:
• Using the Yocto Project: Provides an overview of the components that make up the Yocto Project
followed by information about debugging images created in the Yocto Project.
• A Closer Look at the Yocto Project Development Environment: Provides a more detailed look at the
Yocto Project development environment within the context of development.
• Technical Details: Describes fundamental Yocto Project components as well as an explanation
behind how the Yocto Project uses shared state (sstate) cache to speed build time.
• Migrating to a Newer Yocto Project Release: Describes release-specific information that helps you
move from one Yocto Project Release to another.
• Directory Structure: Describes the Source Directory [http://www.yoctoproject.org/docs/1.8/devmanual/dev-manual.html#source-directory] created either by unpacking a released Yocto
Project tarball on your host development system, or by cloning the upstream Poky [http://
www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#poky] Git repository.
• Classes: Describes the classes used in the Yocto Project.
• Tasks: Describes the tasks defined by the OpenEmbedded build system.
• QA Error and Warning Messages: Lists and describes QA warning and error messages.
• Images: Describes the standard images that the Yocto Project supports.
• Features: Describes mechanisms for creating distribution, machine, and image features during the
build process using the OpenEmbedded build system.
• Variables Glossary: Presents most variables used by the OpenEmbedded build system, which uses
BitBake. Entries describe the function of the variable and how to apply them.
• Variable Context: Provides variable locality or context.
• FAQ: Provides answers for commonly asked questions in the Yocto Project development
environment.
• Contributing to the Yocto Project: Provides guidance on how you can contribute back to the Yocto
Project.

1

Introduction

1.3. System Requirements
For general Yocto Project system requirements, see the "What You Need and How You Get It [http://
www.yoctoproject.org/docs/1.8/yocto-project-qs/yocto-project-qs.html#yp-resources]" section in the
Yocto Project Quick Start. The remainder of this section provides details on system requirements not
covered in the Yocto Project Quick Start.

1.3.1. Supported Linux Distributions
Currently, the Yocto Project is supported on the following distributions:

Note
Yocto Project releases are tested against the stable Linux distributions in the following list. The
Yocto Project should work on other distributions but validation is not performed against them.
In particular, the Yocto Project does not support and currently has no plans to support rollingreleases or development distributions due to their constantly changing nature. We welcome
patches and bug reports, but keep in mind that our priority is on the supported platforms
listed below.
If you encounter problems, please go to Yocto Project Bugzilla [http://
bugzilla.yoctoproject.org] and submit a bug. We are interested in hearing about your
experience.
• Ubuntu 12.04 (LTS)
• Ubuntu 13.10
• Ubuntu 14.04 (LTS)
• Fedora release 19 (Schrödinger's Cat)
• Fedora release 20 (Heisenbug)
• CentOS release 6.4
• CentOS release 6.5
• Debian GNU/Linux 7.0 (Wheezy)
• Debian GNU/Linux 7.1 (Wheezy)
• Debian GNU/Linux 7.2 (Wheezy)
• Debian GNU/Linux 7.3 (Wheezy)
• Debian GNU/Linux 7.4 (Wheezy)
• Debian GNU/Linux 7.5 (Wheezy)
• Debian GNU/Linux 7.6 (Wheezy)
• openSUSE 12.2
• openSUSE 12.3
• openSUSE 13.1

Note
While the Yocto Project Team attempts to ensure all Yocto Project releases are one hundred
percent compatible with each officially supported Linux distribution, instances might exist
where you encounter a problem while using the Yocto Project on a specific distribution.
For example, the CentOS 6.4 distribution does not include the Gtk+ 2.20.0 and PyGtk
2.21.0 (or higher) packages, which are required to run Hob [http://www.yoctoproject.org/
tools-resources/projects/hob].

2

Introduction

1.3.2. Required Packages for the Host Development
System
The list of packages you need on the host development system can be large when covering all
build scenarios using the Yocto Project. This section provides required packages according to Linux
distribution and function.

1.3.2.1. Ubuntu and Debian
The following list shows the required packages by function given a supported Ubuntu or Debian Linux
distribution:
• Essentials: Packages needed to build an image on a headless system:
$ sudo apt-get install gawk wget git-core diffstat unzip texinfo gcc-multilib \
build-essential chrpath socat
• Graphical and Eclipse Plug-In Extras: Packages recommended if the host system has graphics
support or if you are going to use the Eclipse IDE:
$ sudo apt-get install libsdl1.2-dev xterm
• Documentation: Packages needed if you are going to build out the Yocto Project documentation
manuals:
$ sudo apt-get install make xsltproc docbook-utils fop dblatex xmlto
• ADT Installer Extras: Packages needed if you are going to be using the Application Development
Toolkit (ADT) Installer [http://www.yoctoproject.org/docs/1.8/adt-manual/adt-manual.html#usingthe-adt-installer]:
$ sudo apt-get install autoconf automake libtool libglib2.0-dev

1.3.2.2. Fedora Packages
The following list shows the required packages by function given a supported Fedora Linux
distribution:
• Essentials: Packages needed to build an image for a headless system:
$ sudo yum install gawk make wget tar bzip2 gzip python unzip perl patch \
diffutils diffstat git cpp gcc gcc-c++ glibc-devel texinfo chrpath \
ccache perl-Data-Dumper perl-Text-ParseWords perl-Thread-Queue socat
• Graphical and Eclipse Plug-In Extras: Packages recommended if the host system has graphics
support or if you are going to use the Eclipse IDE:
$ sudo yum install SDL-devel xterm perl-Thread-Queue
• Documentation: Packages needed if you are going to build out the Yocto Project documentation
manuals:
$ sudo yum install make docbook-style-dsssl docbook-style-xsl \

3

Introduction

docbook-dtds docbook-utils fop libxslt dblatex xmlto
• ADT Installer Extras: Packages needed if you are going to be using the Application Development
Toolkit (ADT) Installer [http://www.yoctoproject.org/docs/1.8/adt-manual/adt-manual.html#usingthe-adt-installer]:
$ sudo yum install autoconf automake libtool glib2-devel

1.3.2.3. openSUSE Packages
The following list shows the required packages by function given a supported openSUSE Linux
distribution:
• Essentials: Packages needed to build an image for a headless system:
$ sudo zypper install python gcc gcc-c++ git chrpath make wget python-xml \
diffstat texinfo python-curses patch socat
• Graphical and Eclipse Plug-In Extras: Packages recommended if the host system has graphics
support or if you are going to use the Eclipse IDE:
$ sudo zypper install libSDL-devel xterm
• Documentation: Packages needed if you are going to build out the Yocto Project documentation
manuals:
$ sudo zypper install make fop xsltproc dblatex xmlto
• ADT Installer Extras: Packages needed if you are going to be using the Application Development
Toolkit (ADT) Installer [http://www.yoctoproject.org/docs/1.8/adt-manual/adt-manual.html#usingthe-adt-installer]:
$ sudo zypper install autoconf automake libtool glib2-devel

1.3.2.4. CentOS Packages
The following list shows the required packages by function given a supported CentOS Linux
distribution:

Note
For CentOS 6.x, some of the versions of the components provided by the distribution are too
old (e.g. Git, Python, and tar). It is recommended that you install the buildtools in order to
provide versions that will work with the OpenEmbedded build system. For information on how
to install the buildtools tarball, see the "Required Git, Tar, and Python Versions" section.
• Essentials: Packages needed to build an image for a headless system:
$ sudo yum install gawk make wget tar bzip2 gzip python unzip perl patch \
diffutils diffstat git cpp gcc gcc-c++ glibc-devel texinfo chrpath socat
• Graphical and Eclipse Plug-In Extras: Packages recommended if the host system has graphics
support or if you are going to use the Eclipse IDE:

4

Introduction

$ sudo yum install SDL-devel xterm
• Documentation: Packages needed if you are going to build out the Yocto Project documentation
manuals:
$ sudo yum install make docbook-style-dsssl docbook-style-xsl \
docbook-dtds docbook-utils fop libxslt dblatex xmlto
• ADT Installer Extras: Packages needed if you are going to be using the Application Development
Toolkit (ADT) Installer [http://www.yoctoproject.org/docs/1.8/adt-manual/adt-manual.html#usingthe-adt-installer]:
$ sudo yum install autoconf automake libtool glib2-devel

1.3.3. Required Git, tar, and Python Versions
In order to use the build system, your host development system must meet the following version
requirements for Git, tar, and Python:
• Git 1.7.8 or greater
• tar 1.24 or greater
• Python 2.7.3 or greater not including Python 3.x, which is not supported.
If your host development system does not meet all these requirements, you can resolve this by
installing a buildtools tarball that contains these tools. You can get the tarball one of two ways:
download a pre-built tarball or use BitBake to build the tarball.

1.3.3.1. Downloading a Pre-Builtbuildtools Tarball
Downloading and running a pre-built buildtools installer is the easiest of the two methods by which
you can get these tools:
1. Locate and download the *.sh at http://downloads.yoctoproject.org/releases/yocto/yocto-1.8/
buildtools/.
2. Execute the installation script. Here is an example:
$ sh poky-eglibc-x86_64-buildtools-tarball-x86_64-buildtools-nativesdk-standalone-1.8.sh
During execution, a prompt appears that allows you to choose the installation directory. For
example, you could choose the following:
/home/your-username/buildtools
3. Source the tools environment setup script by using a command like the following:
$ source /home/your-username/buildtools/environment-setup-i586-poky-linux
Of course, you need to supply your installation directory and be sure to use the right file (i.e. i585
or x86-64).
After you have sourced the setup script, the tools are added to PATH and any other environment
variables required to run the tools are initialized. The results are working versions versions of Git,
tar, Python and chrpath.

5

Introduction

1.3.3.2. Building Your Ownbuildtools Tarball
Building and running your own buildtools installer applies only when you have a build host that can
already run BitBake. In this case, you use that machine to build the .sh file and then take steps to
transfer and run it on a machine that does not meet the minimal Git, tar, and Python requirements.
Here are the steps to take to build and run your own buildtools installer:
1. On the machine that is able to run BitBake, be sure you have set up your build environment with
the setup script (oe-init-build-env or oe-init-build-env-memres).
2. Run the BitBake command to build the tarball:
$ bitbake buildtools-tarball

Note
The SDKMACHINE variable in your local.conf file determines whether you build tools for
a 32-bit or 64-bit system.
Once the build completes, you can find the .sh file that installs the tools in the tmp/deploy/
sdk subdirectory of the Build Directory [http://www.yoctoproject.org/docs/1.8/dev-manual/devmanual.html#build-directory]. The installer file has the string "buildtools" in the name.
3. Transfer the .sh file from the build host to the machine that does not meet the Git, tar, or Python
requirements.
4. On the machine that does not meet the requirements, run the .sh file to install the tools. Here
is an example:
$ sh poky-eglibc-x86_64-buildtools-tarball-x86_64-buildtools-nativesdk-standalone-1.8.sh
During execution, a prompt appears that allows you to choose the installation directory. For
example, you could choose the following:
/home/your-username/buildtools
5. Source the tools environment setup script by using a command like the following:
$ source /home/your-username/buildtools/environment-setup-i586-poky-linux
Of course, you need to supply your installation directory and be sure to use the right file (i.e. i585
or x86-64).
After you have sourced the setup script, the tools are added to PATH and any other environment
variables required to run the tools are initialized. The results are working versions versions of Git,
tar, Python and chrpath.

1.4. Obtaining the Yocto Project
The Yocto Project development team makes the Yocto Project available through a number of methods:
• Source Repositories: Working from a copy of the upstream poky repository is the preferred method
for obtaining and using a Yocto Project release. You can view the Yocto Project Source Repositories
at http://git.yoctoproject.org/cgit.cgi. In particular, you can find the poky repository at http://
git.yoctoproject.org/cgit/cgit.cgi/poky/.
• Releases:
Stable,
tested
releases
are
downloads.yoctoproject.org/releases/yocto/.
6

available

as

tarballs

through

http://

Introduction

• Nightly Builds: These tarball releases are available at http://autobuilder.yoctoproject.org/nightly.
These builds include Yocto Project releases, meta-toolchain tarball installation scripts, and
experimental builds.
• Yocto Project Website: You can find tarball releases of the Yocto Project and supported BSPs at the
Yocto Project website [http://www.yoctoproject.org]. Along with these downloads, you can find lots
of other information at this site.

1.5. Development Checkouts
Development using the Yocto Project requires a local Source Directory [http://www.yoctoproject.org/
docs/1.8/dev-manual/dev-manual.html#source-directory]. You can set up the Source Directory
by cloning a copy of the upstream poky [http://www.yoctoproject.org/docs/1.8/dev-manual/devmanual.html#poky] Git repository. For information on how to do this, see the "Getting Set Up
[http://www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#getting-setup]" section in the
Yocto Project Development Manual.

7

Chapter 2. Using the Yocto Project
This chapter describes common usage for the Yocto Project. The information is introductory in nature
as other manuals in the Yocto Project documentation set provide more details on how to use the
Yocto Project.

2.1. Running a Build
This section provides a summary of the build process and provides information for less obvious
aspects of the build process. For general information on how to build an image using the
OpenEmbedded build system, see the "Building an Image [http://www.yoctoproject.org/docs/1.8/
yocto-project-qs/yocto-project-qs.html#building-image]" section of the Yocto Project Quick Start.

2.1.1. Build Overview
The first thing you need to do is set up the OpenEmbedded build environment by sourcing an
environment setup script (i.e. oe-init-build-env or oe-init-build-env-memres). Here is an
example:
$ source oe-init-build-env [build_dir]
The build_dir argument is optional and specifies the directory the OpenEmbedded build system
uses for the build - the Build Directory [http://www.yoctoproject.org/docs/1.8/dev-manual/devmanual.html#build-directory]. If you do not specify a Build Directory, it defaults to a directory named
build in your current working directory. A common practice is to use a different Build Directory for
different targets. For example, ~/build/x86 for a qemux86 target, and ~/build/arm for a qemuarm
target.
Once the build environment is set up, you can build a target using:
$ bitbake target
The target is the name of the recipe you want to build. Common targets are the images in meta/
recipes-core/images, meta/recipes-sato/images, etc. all found in the Source Directory [http://
www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#source-directory]. Or, the target can
be the name of a recipe for a specific piece of software such as BusyBox. For more details about the
images the OpenEmbedded build system supports, see the "Images" chapter.

Note
Building an image without GNU General Public License Version 3 (GPLv3), or similarly licensed,
components is supported for only minimal and base images. See the "Images" chapter for
more information.

2.1.2. Building an Image Using GPL Components
When building an image using GPL components, you need to maintain your original settings and not
switch back and forth applying different versions of the GNU General Public License. If you rebuild
using different versions of GPL, dependency errors might occur due to some components not being
rebuilt.

2.2. Installing and Using the Result
Once an image has been built, it often needs to be installed. The images and kernels built by
the OpenEmbedded build system are placed in the Build Directory [http://www.yoctoproject.org/
docs/1.8/dev-manual/dev-manual.html#build-directory] in tmp/deploy/images. For information on
how to run pre-built images such as qemux86 and qemuarm, see the "Using Pre-Built Binaries
and QEMU [http://www.yoctoproject.org/docs/1.8/yocto-project-qs/yocto-project-qs.html#using-pre-

8

Using the Yocto Project

built]" section in the Yocto Project Quick Start. For information about how to install these images, see
the documentation for your particular board or machine.

2.3. Debugging Build Failures
The exact method for debugging build failures depends on the nature of the problem and on the
system's area from which the bug originates. Standard debugging practices such as comparison
against the last known working version with examination of the changes and the re-application of
steps to identify the one causing the problem are valid for the Yocto Project just as they are for
any other system. Even though it is impossible to detail every possible potential failure, this section
provides some general tips to aid in debugging.
A useful feature for debugging is the error reporting tool. Configuring the Yocto Project to use this
tool causes the OpenEmbedded build system to produce error reporting commands as part of the
console output. You can enter the commands after the build completes to log error information into a
common database, that can help you figure out what might be going wrong. For information on how
to enable and use this feature, see the "Using the Error Reporting Tool [http://www.yoctoproject.org/
docs/1.8/dev-manual/dev-manual.html#using-the-error-reporting-tool]" section in the Yocto Project
Development Manual.
For discussions on debugging, see the "Debugging With the GNU Project Debugger
(GDB) Remotely [http://www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#platdev-gdbremotedebug]" and "Working within Eclipse [http://www.yoctoproject.org/docs/1.8/dev-manual/devmanual.html#adt-eclipse]" sections in the Yocto Project Development Manual.

Note
The remainder of this section presents many examples of the bitbake command. You
can learn about BitBake by reading the BitBake User Manual [http://www.yoctoproject.org/
docs/1.8/bitbake-user-manual/bitbake-user-manual.html#bitbake-user-manual].

2.3.1. Task Failures
The log file for shell tasks is available in ${WORKDIR}/temp/log.do_taskname.pid. For example, the
do_compile task for the QEMU minimal image for the x86 machine (qemux86) might be tmp/work/
qemux86-poky-linux/core-image-minimal/1.0-r0/temp/log.do_compile.20830. To see what
BitBake [http://www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#bitbake-term] runs to
generate that log, look at the corresponding run.do_taskname.pid file located in the same directory.
Presently, the output from Python tasks is sent directly to the console.

2.3.2. Running Specific Tasks
Any given package consists of a set of tasks. The standard BitBake behavior in most
cases is: do_fetch, do_unpack, do_patch, do_configure, do_compile, do_install, do_package,
do_package_write_*, and do_build. The default task is do_build and any tasks on which it depends
build first. Some tasks, such as do_devshell, are not part of the default build chain. If you wish to
run a task that is not part of the default build chain, you can use the -c option in BitBake. Here is
an example:
$ bitbake matchbox-desktop -c devshell
If you wish to rerun a task, use the -f force option. For example, the following sequence forces
recompilation after changing files in the work directory.
$ bitbake matchbox-desktop
.
.
make some changes to the source code in the work directory
.
.

9

Using the Yocto Project

$ bitbake matchbox-desktop -c compile -f
$ bitbake matchbox-desktop
This sequence first builds and then recompiles matchbox-desktop. The last command reruns all tasks
(basically the packaging tasks) after the compile. BitBake recognizes that the do_compile task was
rerun and therefore understands that the other tasks also need to be run again.
You can view a list of tasks in a given package by running the do_listtasks task as follows:
$ bitbake matchbox-desktop -c listtasks
The results appear as output to the console and are also in the file ${WORKDIR}/temp/
log.do_listtasks.

2.3.3. Dependency Graphs
Sometimes it can be hard to see why BitBake wants to build other packages before building a given
package you have specified. The bitbake -g targetname command creates the pn-buildlist,
pn-depends.dot, package-depends.dot, and task-depends.dot files in the current directory. These
files show what will be built and the package and task dependencies, which are useful for debugging
problems. You can use the bitbake -g -u depexp targetname command to display the results in
a more human-readable form.

2.3.4. General BitBake Problems
You can see debug output from BitBake by using the -D option. The debug output gives more
information about what BitBake is doing and the reason behind it. Each -D option you use increases
the logging level. The most common usage is -DDD.
The output from bitbake -DDD -v targetname can reveal why BitBake chose a certain version of a
package or why BitBake picked a certain provider. This command could also help you in a situation
where you think BitBake did something unexpected.

2.3.5. Development Host System Issues
Sometimes issues on the host development system can cause your build to fail. Following are known,
host-specific problems. Be sure to always consult the Release Notes [http://www.yoctoproject.org/
download/yocto-project-18-poky-1300] for a look at all release-related issues.
• eglibc-initial fails to build: If your development host system has the unpatched GNU Make 3.82,
the do_install task fails for eglibc-initial during the build.
Typically, every distribution that ships GNU Make 3.82 as the default already has the patched
version. However, some distributions, such as Debian, have GNU Make 3.82 as an option, which
is unpatched. You will see this error on these types of distributions. Switch to GNU Make 3.81 or
patch your make to solve the problem.

2.3.6. Building with No Dependencies
To build a specific recipe (.bb file), you can use the following command form:
$ bitbake -b somepath/somerecipe.bb
This command form does not check for dependencies. Consequently, you should use it only when
you know existing dependencies have been met.

Note
You can also specify fragments of the filename. In this case, BitBake checks for a unique
match.

10

Using the Yocto Project

2.3.7. Variables
You can use the -e BitBake option to display the parsing environment for a configuration. The following
displays the general parsing environment:
$ bitbake -e
This next example shows the parsing environment for a specific recipe:
$ bitbake -e recipename

2.3.8. Recipe Logging Mechanisms
Best practices exist while writing recipes that both log build progress and act on build conditions such
as warnings and errors. Both Python and Bash language bindings exist for the logging mechanism:
• Python: For Python functions, BitBake supports several loglevels: bb.fatal, bb.error, bb.warn,
bb.note, bb.plain, and bb.debug.
• Bash: For Bash functions, the same set of loglevels exist and are accessed with a similar syntax:
bbfatal, bberror, bbwarn, bbnote, bbplain, and bbdebug.
For guidance on how logging is handled in both Python and Bash recipes, see the logging.bbclass
file in the meta/classes folder of the Source Directory [http://www.yoctoproject.org/docs/1.8/devmanual/dev-manual.html#source-directory].

2.3.8.1. Logging With Python
When creating recipes using Python and inserting code that handles build logs, keep in mind the goal
is to have informative logs while keeping the console as "silent" as possible. Also, if you want status
messages in the log, use the "debug" loglevel.
Following is an example written in Python. The code handles logging for a function that determines
the number of tasks needed to be run. See the "do_listtasks" section for additional information:
python do_listtasks() {
bb.debug(2, "Starting to figure out the task list")
if noteworthy_condition:
bb.note("There are 47 tasks to run")
bb.debug(2, "Got to point xyz")
if warning_trigger:
bb.warn("Detected warning_trigger, this might be a problem later.")
if recoverable_error:
bb.error("Hit recoverable_error, you really need to fix this!")
if fatal_error:
bb.fatal("fatal_error detected, unable to print the task list")
bb.plain("The tasks present are abc")
bb.debug(2, "Finished figuring out the tasklist")
}

2.3.8.2. Logging With Bash
When creating recipes using Bash and inserting code that handles build logs, you have the same
goals - informative with minimal console output. The syntax you use for recipes written in Bash is
similar to that of recipes written in Python described in the previous section.
Following is an example written in Bash. The code logs the progress of the do_my_function function.
do_my_function() {

11

Using the Yocto Project

bbdebug 2 "Running do_my_function"
if [ exceptional_condition ]; then
bbnote "Hit exceptional_condition"
fi
bbdebug 2 "Got to point xyz"
if [ warning_trigger ]; then
bbwarn "Detected warning_trigger, this might cause a problem later."
fi
if [ recoverable_error ]; then
bberror "Hit recoverable_error, correcting"
fi
if [ fatal_error ]; then
bbfatal "fatal_error detected"
fi
bbdebug 2 "Completed do_my_function"
}

2.3.9. Other Tips
Here are some other tips that you might find useful:
• When adding new packages, it is worth watching for undesirable items making their way into
compiler command lines. For example, you do not want references to local system files like /usr/
lib/ or /usr/include/.
• If you want to remove the psplash boot splashscreen, add psplash=false to the kernel command
line. Doing so prevents psplash from loading and thus allows you to see the console. It is also
possible to switch out of the splashscreen by switching the virtual console (e.g. Fn+Left or Fn+Right
on a Zaurus).

2.4. Maintaining Build Output Quality
Many factors can influence the quality of a build. For example, if you upgrade a recipe to use a new
version of an upstream software package or you experiment with some new configuration options,
subtle changes can occur that you might not detect until later. Consider the case where your recipe
is using a newer version of an upstream package. In this case, a new version of a piece of software
might introduce an optional dependency on another library, which is auto-detected. If that library has
already been built when the software is building, the software will link to the built library and that
library will be pulled into your image along with the new software even if you did not want the library.
The buildhistory class exists to help you maintain the quality of your build output. You can use the
class to highlight unexpected and possibly unwanted changes in the build output. When you enable
build history, it records information about the contents of each package and image and then commits
that information to a local Git repository where you can examine the information.
The remainder of this section describes the following:
• How you can enable and disable build history
• How to understand what the build history contains
• How to limit the information used for build history
• How to examine the build history from both a command-line and web interface

2.4.1. Enabling and Disabling Build History
Build history is disabled by default. To enable it, add the following INHERIT statement and set the
BUILDHISTORY_COMMIT variable to "1" at the end of your conf/local.conf file found in the Build
Directory [http://www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#build-directory]:
INHERIT += "buildhistory"
BUILDHISTORY_COMMIT = "1"

12

Using the Yocto Project

Enabling build history as previously described causes the build process to collect build output
information and commit it to a local Git [http://www.yoctoproject.org/docs/1.8/dev-manual/devmanual.html#git] repository.

Note
Enabling build history increases your build times slightly, particularly for images, and
increases the amount of disk space used during the build.
You can disable build history by removing the previous statements from your conf/local.conf file.

2.4.2. Understanding What the Build History Contains
Build history information is kept in ${TOPDIR}/buildhistory in the Build Directory as
defined by the BUILDHISTORY_DIR variable. The following is an example abbreviated listing:

At the top level, there is a metadata-revs file that lists the revisions of the repositories for the layers
enabled when the build was produced. The rest of the data splits into separate packages, images
and sdk directories, the contents of which are described below.

2.4.2.1. Build History Package Information
The history for each package contains a text file that has name-value pairs with information about
the package. For example, buildhistory/packages/core2-poky-linux/busybox/busybox/latest
contains the following:
PV = 1.19.3
PR = r3
RDEPENDS = update-rc.d eglibc (>= 2.13)
RRECOMMENDS = busybox-syslog busybox-udhcpc
PKGSIZE = 564701
FILES = /usr/bin/* /usr/sbin/* /usr/libexec/* /usr/lib/lib*.so.* \
/etc /com /var /bin/* /sbin/* /lib/*.so.* /usr/share/busybox \
/usr/lib/busybox/* /usr/share/pixmaps /usr/share/applications \
/usr/share/idl /usr/share/omf /usr/share/sounds /usr/lib/bonobo/servers
FILELIST = /etc/busybox.links /etc/init.d/hwclock.sh /bin/busybox /bin/sh

13

Using the Yocto Project

Most of these name-value pairs correspond to variables used to produce the package. The exceptions
are FILELIST, which is the actual list of files in the package, and PKGSIZE, which is the total size of
files in the package in bytes.
There is also a file corresponding to the recipe from which the package came (e.g. buildhistory/
packages/core2-poky-linux/busybox/latest):
PV = 1.19.3
PR = r3
DEPENDS = virtual/i586-poky-linux-gcc virtual/i586-poky-linux-compilerlibs \
virtual/libc update-rc.d-native
PACKAGES = busybox-httpd busybox-udhcpd busybox-udhcpc busybox-syslog \
busybox-mdev busybox-dbg busybox busybox-doc busybox-dev \
busybox-staticdev busybox-locale
Finally, for those recipes fetched from a version control system (e.g., Git), a file exists that lists source
revisions that are specified in the recipe and lists the actual revisions used during the build. Listed
and actual revisions might differ when SRCREV is set to ${AUTOREV}. Here is an example assuming
buildhistory/packages/emenlow-poky-linux/linux-yocto/latest_srcrev):
# SRCREV_machine = "b5c37fe6e24eec194bb29d22fdd55d73bcc709bf"
SRCREV_machine = "b5c37fe6e24eec194bb29d22fdd55d73bcc709bf"
# SRCREV_emgd = "caea08c988e0f41103bbe18eafca20348f95da02"
SRCREV_emgd = "caea08c988e0f41103bbe18eafca20348f95da02"
# SRCREV_meta = "c2ed0f16fdec628242a682897d5d86df4547cf24"
SRCREV_meta = "c2ed0f16fdec628242a682897d5d86df4547cf24"
You can use the buildhistory-collect-srcrevs command to collect the stored SRCREV values from
build history and report them in a format suitable for use in global configuration (e.g., local.conf
or a distro include file) to override floating AUTOREV values to a fixed set of revisions. Here is some
example output from this command:
# emenlow-poky-linux
SRCREV_machine_pn-linux-yocto = "b5c37fe6e24eec194bb29d22fdd55d73bcc709bf"
SRCREV_emgd_pn-linux-yocto = "caea08c988e0f41103bbe18eafca20348f95da02"
SRCREV_meta_pn-linux-yocto = "c2ed0f16fdec628242a682897d5d86df4547cf24"
# core2-poky-linux
SRCREV_pn-kmod = "62081c0f68905b22f375156d4532fd37fa5c8d33"
SRCREV_pn-blktrace = "d6918c8832793b4205ed3bfede78c2f915c23385"
SRCREV_pn-opkg = "649"

Note
Here are some notes on using the buildhistory-collect-srcrevs command:
• By default, only values where the SRCREV was not hardcoded (usually when AUTOREV was
used) are reported. Use the -a option to see all SRCREV values.
• The output statements might not have any effect if overrides are applied elsewhere in the
build system configuration. Use the -f option to add the forcevariable override to each
output line if you need to work around this restriction.
• The script does apply special handling when building for multiple machines. However, the
script does place a comment before each set of values that specifies which triplet to which
they belong as shown above (e.g., emenlow-poky-linux).

2.4.2.2. Build History Image Information
The files produced for each image are as follows:

14

Using the Yocto Project

• image-files: A directory containing selected files from the root filesystem. The files are defined
by BUILDHISTORY_IMAGE_FILES.
• build-id.txt: Human-readable information about the build configuration and metadata source
revisions. This file contains the full build header as printed by BitBake.
• *.dot: Dependency graphs for the image that are compatible with graphviz.
• files-in-image.txt: A list of files in the image with permissions, owner, group, size, and symlink
information.
• image-info.txt: A text file containing name-value pairs with information about the image. See
the following listing example for more information.
• installed-package-names.txt: A list of installed packages by name only.
• installed-package-sizes.txt: A list of installed packages ordered by size.
• installed-packages.txt: A list of installed packages with full package filenames.

Note
Installed package information is able to be gathered and produced even if package
management is disabled for the final image.
Here is an example of image-info.txt:
DISTRO = poky
DISTRO_VERSION = 1.1+snapshot-20120207
USER_CLASSES = image-mklibs image-prelink
IMAGE_CLASSES = image_types
IMAGE_FEATURES = debug-tweaks x11-base apps-x11-core \
package-management ssh-server-dropbear package-management
IMAGE_LINGUAS = en-us en-gb
IMAGE_INSTALL = packagegroup-core-boot packagegroup-base-extended
BAD_RECOMMENDATIONS =
ROOTFS_POSTPROCESS_COMMAND = buildhistory_get_image_installed ;
rootfs_update_timestamp ;
IMAGE_POSTPROCESS_COMMAND = buildhistory_get_imageinfo ;
IMAGESIZE = 171816
Other than IMAGESIZE, which is the total size of the files in the image in Kbytes, the name-value pairs
are variables that may have influenced the content of the image. This information is often useful
when you are trying to determine why a change in the package or file listings has occurred.

2.4.2.3. Using Build History to Gather Image Information Only
As you can see, build history produces image information, including dependency graphs, so you
can see why something was pulled into the image. If you are just interested in this information
and not interested in collecting specific package or SDK information, you can enable writing only
image information without any history by adding the following to your conf/local.conf file found
in the Build Directory [http://www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#builddirectory]:
INHERIT += "buildhistory"
BUILDHISTORY_COMMIT = "0"
BUILDHISTORY_FEATURES = "image"
Here, you set the BUILDHISTORY_FEATURES variable to use the image feature only.

2.4.2.4. Build History SDK Information
Build history collects similar information on the contents of SDKs (e.g. meta-toolchain or bitbake
-c populate_sdk imagename) as compared to information it collects for images. The following list
shows the files produced for each SDK:

15

Using the Yocto Project

• files-in-sdk.txt: A list of files in the SDK with permissions, owner, group, size, and symlink
information. This list includes both the host and target parts of the SDK.
• sdk-info.txt: A text file containing name-value pairs with information about the SDK. See the
following listing example for more information.
• The following information appears under each of the host and target directories for the portions
of the SDK that run on the host and on the target, respectively:
• depends.dot: Dependency graph for the SDK that is compatible with graphviz.
• installed-package-names.txt: A list of installed packages by name only.
• installed-package-sizes.txt: A list of installed packages ordered by size.
• installed-packages.txt: A list of installed packages with full package filenames.
Here is an example of sdk-info.txt:
DISTRO = poky
DISTRO_VERSION = 1.3+snapshot-20130327
SDK_NAME = poky-eglibc-i686-arm
SDK_VERSION = 1.3+snapshot
SDKMACHINE =
SDKIMAGE_FEATURES = dev-pkgs dbg-pkgs
BAD_RECOMMENDATIONS =
SDKSIZE = 352712
Other than SDKSIZE, which is the total size of the files in the SDK in Kbytes, the name-value pairs are
variables that might have influenced the content of the SDK. This information is often useful when
you are trying to determine why a change in the package or file listings has occurred.

2.4.2.5. Examining Build History Information
You can examine build history output from the command line or from a web interface.
To see any changes that have occurred (assuming you have BUILDHISTORY_COMMIT = "1"), you can
simply use any Git command that allows you to view the history of a repository. Here is one method:
$ git log -p
You need to realize, however, that this method does show changes that are not significant (e.g. a
package's size changing by a few bytes).
A command-line tool called buildhistory-diff does exist, though, that queries the Git repository
and prints just the differences that might be significant in human-readable form. Here is an example:
$ ~/poky/poky/scripts/buildhistory-diff . HEAD^
Changes to images/qemux86_64/eglibc/core-image-minimal (files-in-image.txt):
/etc/anotherpkg.conf was added
/sbin/anotherpkg was added
* (installed-package-names.txt):
*
anotherpkg was added
Changes to images/qemux86_64/eglibc/core-image-minimal (installed-package-names.txt):
anotherpkg was added
packages/qemux86_64-poky-linux/v86d: PACKAGES: added "v86d-extras"
* PR changed from "r0" to "r1"
* PV changed from "0.1.10" to "0.1.12"
packages/qemux86_64-poky-linux/v86d/v86d: PKGSIZE changed from 110579 to 144381 (+30%)
* PR changed from "r0" to "r1"
* PV changed from "0.1.10" to "0.1.12"

16

Using the Yocto Project

To see changes to the build history using a web interface, follow the instruction in the README file
here. http://git.yoctoproject.org/cgit/cgit.cgi/buildhistory-web/.
Here

is

a

sample

screenshot

of

the

interface:

2.5. Speeding Up the Build
Build time can be an issue. By default, the build system uses three simple controls to try and maximize
build efficiency:
• BB_NUMBER_THREADS
• BB_NUMBER_PARSE_THREADS [http://www.yoctoproject.org/docs/1.8/bitbake-user-manual/bitbakeuser-manual.html#var-BB_NUMBER_PARSE_THREADS]
• PARALLEL_MAKE
These three variables all scale to the number of processor cores available on the build system.
This auto-scaling ensures that the build system fundamentally takes advantage of potential parallel
operations during the build based on the build machine's capabilities.

17

Using the Yocto Project

If you need to achieve even faster builds than what the build system produces by default, you can
consider and implement some of the following:
• BB_NUMBER_THREADS, BB_NUMBER_PARSE_THREADS, and PARALLEL_MAKE: As previously mentioned,
the build system scales the values for these variables. However, you can manually override them
in your local.conf file if you are not satisfied with the defaults.
• File system type: The file system type that the build is being performed on can also influence
performance. Using ext4 is recommended as compared to ext2 and ext3 due to ext4 improved
features such as extents.
• Disabling the updating of access time using noatime: The noatime mount option prevents the build
system from updating file and directory access times.
• Setting a longer commit: Using the "commit=" mount option increases the interval in seconds
between disk cache writes. Changing this interval from the five second default to something longer
increases the risk of data loss but decreases the need to write to the disk, thus increasing the build
performance.
• Choosing the packaging backend: Of the available packaging backends, IPK is the fastest.
Additionally, selecting a singular packaging backend also helps.
• Using /tmp as a temporary file system: While this can help speed up the build, the benefits
are limited due to the compiler using -pipe. The build system goes to some lengths to
avoid sync() calls into the file system on the principle that if there was a significant failure,
the Build Directory [http://www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#builddirectory] contents could easily be rebuilt.
• Inheriting the rm_work class: Inheriting this class has shown to speed up builds due to significantly
lower amounts of data stored in the data cache as well as on disk. Inheriting this class also makes
cleanup of TMPDIR faster, at the expense of being easily able to dive into the source code. File
system maintainers have recommended that the fastest way to clean up large numbers of files is
to reformat partitions rather than delete files due to the linear nature of partitions. This, of course,
assumes you structure the disk partitions and file systems in a way that this is practical.
Aside from the previous list, you should keep some trade offs in mind that can help you speed up
the build:
• Exclude debug symbols and other debug information: If you do not need these symbols and other
debug information, disabling the *-dbg package generation can speed up the build. You can disable
this generation by setting the INHIBIT_PACKAGE_DEBUG_SPLIT variable to "1".
• Disable static library generation for recipes derived from autoconf or libtool: Following is an
example showing how to disable static libraries and still provide an override to handle exceptions:
STATICLIBCONF = "--disable-static"
STATICLIBCONF_sqlite3-native = ""
EXTRA_OECONF += "${STATICLIBCONF}"

Notes
• Some recipes need static libraries in order to work correctly (e.g. pseudo-native needs
sqlite3-native). Overrides, as in the previous example, account for these kinds of
exceptions.
• Some packages have packaging code that assumes the presence of the static libraries.
If so, you might need to exclude them as well.

18

Chapter 3. A Closer Look at
the Yocto Project Development
Environment
This chapter takes a more detailed look at the Yocto Project development environment. The
following diagram represents the development environment at a high level. The remainder
of this chapter expands on the fundamental input, output, process, and Metadata [http://
www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#metadata]) blocks in the Yocto Project
development environment.

The generalized Yocto Project Development Environment consists of several functional areas:
• User Configuration: Metadata you can use to control the build process.
• Metadata Layers: Various layers that provide software, machine, and distro Metadata.
• Source Files: Upstream releases, local projects, and SCMs.
• Build System: Processes under the control of BitBake [http://www.yoctoproject.org/docs/1.8/devmanual/dev-manual.html#bitbake-term]. This block expands on how BitBake fetches source,
applies patches, completes compilation, analyzes output for package generation, creates and tests
packages, generates images, and generates cross-development tools.
• Package Feeds: Directories containing output packages (RPM, DEB or IPK), which are subsequently
used in the construction of an image or SDK, produced by the build system. These feeds can also be
copied and shared using a web server or other means to facilitate extending or updating existing
images on devices at runtime if runtime package management is enabled.
• Images: Images produced by the development process.
• Application Development SDK: Cross-development tools that are produced along with an image or
separately with BitBake.

19

A Closer Look at the Yocto Project Development Environment

3.1. User Configuration
User configuration helps define the build. Through user configuration, you can tell BitBake the target
architecture for which you are building the image, where to store downloaded source, and other build
properties.
The following figure shows an expanded representation of the "User Configuration" box of the general
Yocto Project Development Environment figure [19]:

BitBake needs some basic configuration files in order to complete a build. These files are *.conf
files. The minimally necessary ones reside as example files in the Source Directory [http://
www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#source-directory]. For simplicity, this
section refers to the Source Directory as the "Poky Directory."
When you clone the poky Git repository or you download and unpack a Yocto Project release, you can
set up the Source Directory to be named anything you want. For this discussion, the cloned repository
uses the default name poky.

Note
The Poky repository is primarily an aggregation of existing repositories. It is not a canonical
upstream source.
The meta-yocto layer inside Poky contains a conf directory that has example configuration files.
These example files are used as a basis for creating actual configuration files when you source the
build environment script (i.e. oe-init-build-env or oe-init-build-env-memres).
Sourcing the build environment script creates a Build Directory [http://www.yoctoproject.org/docs/1.8/
dev-manual/dev-manual.html#build-directory] if one does not already exist. BitBake uses the Build
Directory for all its work during builds. The Build Directory has a conf directory that contains default
versions of your local.conf and bblayers.conf configuration files. These default configuration files
are created only if versions do not already exist in the Build Directory at the time you source the
build environment setup script.
Because the Poky repository is fundamentally an aggregation of existing repositories, some users
might be familiar with running the oe-init-build-env or oe-init-build-env-memres script in
the context of separate OpenEmbedded-Core and BitBake repositories rather than a single Poky
repository. This discussion assumes the script is executed from within a cloned or unpacked version
of Poky.
Depending on where the script is sourced, different sub-scripts are called to set up the Build Directory
(Yocto or OpenEmbedded). Specifically, the script scripts/oe-setup-builddir inside the poky

20

A Closer Look at the Yocto Project Development Environment

directory sets up the Build Directory and seeds the directory (if necessary) with configuration files
appropriate for the Yocto Project development environment.

Note
The scripts/oe-setup-builddir script uses the $TEMPLATECONF variable to determine
which sample configuration files to locate.
The local.conf file provides many basic variables that define a build environment. Here is a list of
a few. To see the default configurations in a local.conf file created by the build environment script,
see the local.conf.sample in the meta-yocto layer:
• Parallelism Options: Controlled by the BB_NUMBER_THREADS and PARALLEL_MAKE variables.
• Target Machine Selection: Controlled by the MACHINE variable.
• Download Directory: Controlled by the DL_DIR variable.
• Shared State Directory: Controlled by the SSTATE_DIR variable.
• Build Output: Controlled by the TMPDIR variable.

Note
Configurations set in the conf/local.conf file can also be set in the conf/site.conf and
conf/auto.conf configuration files.
The bblayers.conf file tells BitBake what layers you want considered during the build. By default,
the layers listed in this file include layers minimally needed by the build system. However, you must
manually add any custom layers you have created. You can find more information on working with the
bblayers.conf file in the "Enabling Your Layer [http://www.yoctoproject.org/docs/1.8/dev-manual/
dev-manual.html#enabling-your-layer]" section in the Yocto Project Development Manual.
The files site.conf and auto.conf are not created by the environment initialization script. If you
want these configuration files, you must create them yourself:
• site.conf: You can use the conf/site.conf configuration file to configure multiple build
directories. For example, suppose you had several build environments and they shared some
common features. You can set these default build properties here. A good example is perhaps the
level of parallelism you want to use through the BB_NUMBER_THREADS and PARALLEL_MAKE variables.
One useful scenario for using the conf/site.conf file is to extend your BBPATH variable to include
the path to a conf/site.conf. Then, when BitBake looks for Metadata using BBPATH, it finds
the conf/site.conf file and applies your common configurations found in the file. To override
configurations in a particular build directory, alter the similar configurations within that build
directory's conf/local.conf file.
• auto.conf: This file is not hand-created. Rather, the file is usually created and written to by an
autobuilder. The settings put into the file are typically the same as you would find in the conf/
local.conf or the conf/site.conf files.
You can edit all configuration files to further define any particular build environment. This process is
represented by the "User Configuration Edits" box in the figure.
When you launch your build with the bitbake target command, BitBake sorts out the configurations
to ultimately define your build environment.

3.2. Metadata, Machine Configuration, and
Policy Configuration
The previous section described the user configurations that define BitBake's global behavior. This
section takes a closer look at the layers the build system uses to further control the build. These
layers provide Metadata for the software, machine, and policy.
In general, three types of layer input exist:
• Policy Configuration: Distribution Layers provide top-level or general policies for the image or SDK
being built. For example, this layer would dictate whether BitBake produces RPM or IPK packages.

21

A Closer Look at the Yocto Project Development Environment

• Machine Configuration: Board Support Package (BSP) layers provide machine configurations. This
type of information is specific to a particular target architecture.
• Metadata: Software layers contain user-supplied recipe files, patches, and append files.
The following figure shows an expanded representation of the Metadata, Machine Configuration,
and Policy Configuration input (layers) boxes of the general Yocto Project Development Environment
figure [19]:

In general, all layers have a similar structure. They all contain a licensing file (e.g. COPYING) if the
layer is to be distributed, a README file as good practice and especially if the layer is to be distributed,
a configuration directory, and recipe directories.

22

A Closer Look at the Yocto Project Development Environment

The Yocto Project has many layers that can be used. You can see a web-interface listing of
them on the Source Repositories [http://git.yoctoproject.org/] page. The layers are shown at the
bottom categorized under "Yocto Metadata Layers." These layers are fundamentally a subset of the
OpenEmbedded Metadata Index [http://layers.openembedded.org/layerindex/layers/], which lists all
layers provided by the OpenEmbedded community.

Note
Layers exist in the Yocto Project Source Repositories that cannot be found in the
OpenEmbedded Metadata Index. These layers are either deprecated or experimental in
nature.
BitBake uses the conf/bblayers.conf file, which is part of the user configuration, to find what layers
it should be using as part of the build.
For
more
information
on
layers,
see
the
"Understanding
and
Creating
Layers
[http://www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#understanding-andcreating-layers]" section in the Yocto Project Development Manual.

3.2.1. Distro Layer
The distribution layer provides policy configurations for your distribution. Best practices dictate
that you isolate these types of configurations into their own layer. Settings you provide in conf/
distro/distro.conf override similar settings that BitBake finds in your conf/local.conf file in the
Build Directory.
The following list provides some explanation and references for what you typically find in the
distribution layer:
• classes: Class files (.bbclass) hold common functionality that can be shared among recipes in the
distribution. When your recipes inherit a class, they take on the settings and functions for that class.
You can read more about class files in the "Classes" section.
• conf: This area holds configuration files for the layer (conf/layer.conf), the distribution (conf/
distro/distro.conf), and any distribution-wide include files.
• recipes-*: Recipes and append files that affect common functionality across the distribution. This
area could include recipes and append files to add distribution-specific configuration, initialization
scripts, custom image recipes, and so forth.

3.2.2. BSP Layer
The BSP Layer provides machine configurations. Everything in this layer is specific to the machine for
which you are building the image or the SDK. A common structure or form is defined for BSP layers.
You can learn more about this structure in the Yocto Project Board Support Package (BSP) Developer's
Guide [http://www.yoctoproject.org/docs/1.8/bsp-guide/bsp-guide.html].

Note
In order for a BSP layer to be considered compliant with the Yocto Project, it must meet some
structural requirements.
The BSP Layer's configuration directory contains configuration files for the machine (conf/
machine/machine.conf) and, of course, the layer (conf/layer.conf).
The remainder of the layer is dedicated to specific recipes by function: recipes-bsp, recipescore, recipes-graphics, and recipes-kernel. Metadata can exist for multiple formfactors, graphics
support systems, and so forth.

Note
While the figure shows several recipes-* directories, not all these directories appear in all
BSP layers.

3.2.3. Software Layer
The software layer provides the Metadata for additional software packages used during the build.
This layer does not include Metadata that is specific to the distribution or the machine, which are
found in their respective layers.

23

A Closer Look at the Yocto Project Development Environment

This layer contains any new recipes that your project needs in the form of recipe files.

3.3. Sources
In order for the OpenEmbedded build system to create an image or any target, it must be able to
access source files. The general Yocto Project Development Environment figure[19] represents
source files using the "Upstream Project Releases", "Local Projects", and "SCMs (optional)" boxes. The
figure represents mirrors, which also play a role in locating source files, with the "Source Mirror(s)"
box.
The method by which source files are ultimately organized is a function of the project. For example,
for released software, projects tend to use tarballs or other archived files that can capture the state of
a release guaranteeing that it is statically represented. On the other hand, for a project that is more
dynamic or experimental in nature, a project might keep source files in a repository controlled by a
Source Control Manager (SCM) such as Git. Pulling source from a repository allows you to control the
point in the repository (the revision) from which you want to build software. Finally, a combination of
the two might exist, which would give the consumer a choice when deciding where to get source files.
BitBake uses the SRC_URI variable to point to source files regardless of their location. Each recipe
must have a SRC_URI variable that points to the source.
Another area that plays a significant role in where source files come from is pointed to by the DL_DIR
variable. This area is a cache that can hold previously downloaded source. You can also instruct
the OpenEmbedded build system to create tarballs from Git repositories, which is not the default
behavior, and store them in the DL_DIR by using the BB_GENERATE_MIRROR_TARBALLS variable.
Judicious use of a DL_DIR directory can save the build system a trip across the Internet when looking
for files. A good method for using a download directory is to have DL_DIR point to an area outside of
your Build Directory. Doing so allows you to safely delete the Build Directory if needed without fear
of removing any downloaded source file.

24

A Closer Look at the Yocto Project Development Environment

The remainder of this section provides a deeper look into the source files and the
mirrors. Here is a more detailed look at the source file area of the base figure:

3.3.1. Upstream Project Releases
Upstream project releases exist anywhere in the form of an archived file (e.g. tarball or zip file). These
files correspond to individual recipes. For example, the figure uses specific releases each for BusyBox,
Qt, and Dbus. An archive file can be for any released product that can be built using a recipe.

3.3.2. Local Projects
Local projects are custom bits of software the user provides. These bits reside somewhere local to a
project - perhaps a directory into which the user checks in items (e.g. a local directory containing a
development source tree used by the group).

25

A Closer Look at the Yocto Project Development Environment

The canonical method through which to include a local project is to use the externalsrc class to
include that local project. You use either the local.conf or a recipe's append file to override or set
the recipe to point to the local directory on your disk to pull in the whole source tree.
For information on how to use the externalsrc class, see the "externalsrc.bbclass" section.

3.3.3. Source Control Managers (Optional)
Another place the build system can get source files from is through an SCM such as Git or Subversion.
In this case, a repository is cloned or checked out. The do_fetch task inside BitBake uses the SRC_URI
variable and the argument's prefix to determine the correct fetcher module.

Note
For information on how to have the OpenEmbedded build system generate tarballs for Git
repositories and place them in the DL_DIR directory, see the BB_GENERATE_MIRROR_TARBALLS
variable.
When fetching a repository, BitBake uses the SRCREV variable to determine the specific revision from
which to build.

3.3.4. Source Mirror(s)
Two kinds of mirrors exist: pre-mirrors and regular mirrors. The PREMIRRORS and MIRRORS variables
point to these, respectively. BitBake checks pre-mirrors before looking upstream for any source files.
Pre-mirrors are appropriate when you have a shared directory that is not a directory defined by the
DL_DIR variable. A Pre-mirror typically points to a shared directory that is local to your organization.
Regular mirrors can be any site across the Internet that is used as an alternative location for source
code should the primary site not be functioning for some reason or another.

3.4. Package Feeds
When the OpenEmbedded build system generates an image or an SDK, it gets the packages from a
package feed area located in the Build Directory [http://www.yoctoproject.org/docs/1.8/dev-manual/
dev-manual.html#build-directory]. The general Yocto Project Development Environment figure[19]
shows this package feeds area in the upper-right corner.

26

A Closer Look at the Yocto Project Development Environment

This
by

section
looks
a
the
build
system.

little
Here

closer
into
the
package
feeds
is
a
more
detailed
look
at

area
the

used
area:

Package feeds are an intermediary step in the build process. BitBake generates packages whose
types are defined by the PACKAGE_CLASSES variable. Before placing the packages into package feeds,
the build process validates them with generated output quality assurance checks through the insane
class.
The package feed area resides in tmp/deploy of the Build Directory. Folders are created that
correspond to the package type (IPK, DEB, or RPM) created. Further organization is derived through
the value of the PACKAGE_ARCH variable for each package. For example, packages can exist for
the i586 or qemux86 architectures. The package files themselves reside within the appropriate
architecture folder.
BitBake uses the do_package_write_* tasks to place generated packages into the package
holding area (e.g. do_package_write_ipk for IPK packages). See the "do_package_write_deb",
"do_package_write_ipk", "do_package_write_rpm", and "do_package_write_tar" sections for
additional information.

3.5. BitBake
The OpenEmbedded build system uses BitBake [http://www.yoctoproject.org/docs/1.8/dev-manual/
dev-manual.html#bitbake-term] to produce images. You can see from the general Yocto Project

27

A Closer Look at the Yocto Project Development Environment

Development Environment figure [19], the BitBake area consists of several functional areas. This
section takes a closer look at each of those areas.
Separate
documentation
exists
for
the
BitBake
tool.
See
the
BitBake User Manual [http://www.yoctoproject.org/docs/1.8/bitbake-user-manual/bitbake-usermanual.html#bitbake-user-manual] for reference material on BitBake.

3.5.1. Source Fetching
The

first

stages

of

building

a

recipe

are

to

fetch

and

unpack

the

source

code:

The do_fetch and do_unpack tasks fetch the source files and unpack them into the work directory.

Note
For every local file (e.g. file://) that is part of a recipe's SRC_URI statement, the
OpenEmbedded build system takes a checksum of the file for the recipe and inserts the
checksum into the signature for the do_fetch. If any local file has been modified, the
do_fetch task and all tasks that depend on it are re-executed.
By default, everything is accomplished in the Build Directory [http://www.yoctoproject.org/docs/1.8/
dev-manual/dev-manual.html#build-directory], which has a defined structure. For additional general
information on the Build Directory, see the "build/" section.
Unpacked source files are pointed to by the S variable. Each recipe has an area in the Build Directory
where the unpacked source code resides. The name of that directory for any given recipe is defined
from several different variables. You can see the variables that define these directories by looking
at the figure:
• TMPDIR - The base directory where the OpenEmbedded build system performs all its work during
the build.
• PACKAGE_ARCH - The architecture of the built package or packages.

28

A Closer Look at the Yocto Project Development Environment

• TARGET_OS - The operating system of the target device.
• PN - The name of the built package.
• PV - The version of the recipe used to build the package.
• PR - The revision of the recipe used to build the package.
• WORKDIR - The location within TMPDIR where a specific package is built.
• S - Contains the unpacked source files for a given recipe.

3.5.2. Patching
Once
patch

source
files

code
and

is
fetched
and
applies
them

unpacked,
to
the

BitBake
source

locates
files:

The do_patch task processes recipes by using the SRC_URI variable to locate applicable patch files,
which by default are *.patch or *.diff files, or any file if "apply=yes" is specified for the file in
SRC_URI.
BitBake finds and applies multiple patches for a single recipe in the order in which it finds the patches.
Patches are applied to the recipe's source files located in the S directory.
For more information on how the source directories are created, see the "Source Fetching" section.

29

A Closer Look at the Yocto Project Development Environment

3.5.3. Configuration and Compilation
After source code is patched, BitBake executes tasks that configure and compile the source code:

This step in the build process consists of three tasks:
• do_configure: This task configures the source by enabling and disabling any build-time and
configuration options for the software being built. Configurations can come from the recipe itself
as well as from an inherited class. Additionally, the software itself might configure itself depending
on the target for which it is being built.
The configurations handled by the do_configure task are specific to source code configuration for
the source code being built by the recipe.
If you are using the autotools class, you can add additional configuration options by using the
EXTRA_OECONF variable. For information on how this variable works within that class, see the meta/
classes/autotools.bbclass file.
• do_compile: Once a configuration task has been satisfied, BitBake compiles the source using the
do_compile task. Compilation occurs in the directory pointed to by the B variable. Realize that the
B directory is, by default, the same as the S directory.
• do_install: Once compilation is done, BitBake executes the do_install task. This task copies
files from the B directory and places them in a holding area pointed to by the D variable.

30

A Closer Look at the Yocto Project Development Environment

3.5.4. Package Splitting
After
source
code
is
system
analyzes
the

configured
and
compiled,
results
and
splits
the

the
OpenEmbedded
build
output
into
packages:

The do_package and do_packagedata tasks combine to analyze the files found in the D directory
and split them into subsets based on available packages and files. The analyzing process involves
the following as well as other items: splitting out debugging symbols, looking at shared library
dependencies between packages, and looking at package relationships. The do_packagedata task
creates package metadata based on the analysis such that the OpenEmbedded build system can
generate the final packages. Working, staged, and intermediate results of the analysis and package
splitting process use these areas:
• PKGD - The destination directory for packages before they are split.
• PKGDATA_DIR - A shared, global-state directory that holds data generated during the packaging
process.

31

A Closer Look at the Yocto Project Development Environment

• PKGDESTWORK - A temporary work area used by the do_package task.
• PKGDEST - The parent directory for packages after they have been split.
The FILES variable defines the files that go into each package in PACKAGES. If you want details on
how this is accomplished, you can look at the package class.
Depending on the type of packages being created (RPM, DEB, or IPK), the do_package_write_* task
creates the actual packages and places them in the Package Feed area, which is ${TMPDIR}/deploy.
You can see the "Package Feeds" section for more detail on that part of the build process.

Note
Support for creating feeds directly from the deploy/* directories does not exist. Creating
such feeds usually requires some kind of feed maintenance mechanism that would upload the
new packages into an official package feed (e.g. the Ångström distribution). This functionality
is highly distribution-specific and thus is not provided out of the box.

32

A Closer Look at the Yocto Project Development Environment

3.5.5. Image Generation
Once
packages
are
split
OpenEmbedded build system

and
stored
in
the
Package
Feeds
area,
the
uses BitBake to generate the root filesystem image:

The image generation process consists of several stages and depends on many variables. The
do_rootfs task uses these key variables to help create the list of packages to actually install:
• IMAGE_INSTALL: Lists out the base set of packages to install from the Package Feeds area.
• PACKAGE_EXCLUDE: Specifies packages that should not be installed.
• IMAGE_FEATURES: Specifies features to include in the image. Most of these features map to
additional packages for installation.
• PACKAGE_CLASSES: Specifies the package backend to use and consequently helps determine where
to locate packages within the Package Feeds area.

33

A Closer Look at the Yocto Project Development Environment

• IMAGE_LINGUAS: Determines the language(s) for which additional language support packages are
installed.
Package installation is under control of the package manager (e.g. smart/rpm, opkg, or apt/dpkg)
regardless of whether or not package management is enabled for the target. At the end of the process,
if package management is not enabled for the target, the package manager's data files are deleted
from the root filesystem.
During image generation, the build system attempts to run all post-installation scripts. Any that
fail to run on the build host are run on the target when the target system is first booted. If
you are using a read-only root filesystem [http://www.yoctoproject.org/docs/1.8/dev-manual/devmanual.html#creating-a-read-only-root-filesystem], all the post installation scripts must succeed
during the package installation phase since the root filesystem is read-only.
During Optimization, optimizing processes are run across the image. These processes include mklibs
and prelink. The mklibs process optimizes the size of the libraries. A prelink process optimizes
the dynamic linking of shared libraries to reduce start up time of executables.
Along with writing out the root filesystem image, the do_rootfs task creates a manifest file
(.manifest) in the same directory as the root filesystem image that lists out, line-by-line, the installed
packages. This manifest file is useful for the testimage class, for example, to determine whether or
not to run specific tests. See the IMAGE_MANIFEST variable for additional information.
Part of the image generation process includes compressing the root filesystem image. Compression is
accomplished through several optimization routines designed to reduce the overall size of the image.
After the root filesystem has been constructed, the image generation process turns everything
into an image file or a set of image files. The formats used for the root filesystem depend on the
IMAGE_FSTYPES variable.

Note
The entire image generation process is run under Pseudo. Running under Pseudo ensures
that the files in the root filesystem have correct ownership.

34

A Closer Look at the Yocto Project Development Environment

3.5.6. SDK Generation
The OpenEmbedded build system uses BitBake to generate the Software Development Kit (SDK)
installer
script:

Note
For more information on the cross-development toolchain generation, see the "CrossDevelopment Toolchain Generation" section. For information on advantages gained
when building a cross-development toolchain using the do_populate_sdk task, see the
"Optionally Building a Toolchain Installer [http://www.yoctoproject.org/docs/1.8/adt-manual/
adt-manual.html#optionally-building-a-toolchain-installer]" section in the Yocto Project
Application Developer's Guide.
Like image generation, the SDK script process consists of several stages and depends on many
variables. The do_populate_sdk task uses these key variables to help create the list of packages to
actually install. For information on the variables listed in the figure, see the "Application Development
SDK" section.

35

A Closer Look at the Yocto Project Development Environment

The do_populate_sdk task handles two parts: a target part and a host part. The target part is the
part built for the target hardware and includes libraries and headers. The host part is the part of the
SDK that runs on the SDKMACHINE.
Once both parts are constructed, the do_populate_sdk task performs some cleanup on both
parts. After the cleanup, the task creates a cross-development environment setup script and any
configuration files that might be needed.
The final output of the task is the Cross-development toolchain installation script (.sh file), which
includes the environment setup script.

3.6. Images
The images produced by the OpenEmbedded build
the root filesystem that are ready to boot on a
the general Yocto Project Development Environment
in part, consists of images. This section is going to

system are compressed forms of
target device. You can see from
figure [19] that BitBake output,
look more closely at this output:

For a list of example images that the Yocto Project provides, see the "Images" chapter.
Images are written out to the Build Directory [http://www.yoctoproject.org/docs/1.8/dev-manual/devmanual.html#build-directory] inside the tmp/deploy/images/machine/ folder as shown in the figure.
This folder contains any files expected to be loaded on the target device. The DEPLOY_DIR variable
points to the deploy directory, while the DEPLOY_DIR_IMAGE variable points to the appropriate
directory containing images for the current configuration.
• kernel-image: A kernel binary file. The KERNEL_IMAGETYPE variable setting determines the naming
scheme for the kernel image file. Depending on that variable, the file could begin with a variety

36

A Closer Look at the Yocto Project Development Environment

of naming strings. The deploy/images/machine directory can contain multiple image files for the
machine.
• root-filesystem-image: Root filesystems for the target device (e.g. *.ext3 or *.bz2 files).
The IMAGE_FSTYPES variable setting determines the root filesystem image type. The deploy/
images/machine directory can contain multiple root filesystems for the machine.
• kernel-modules: Tarballs that contain all the modules built for the kernel. Kernel module tarballs
exist for legacy purposes and can be suppressed by setting the MODULE_TARBALL_DEPLOY variable
to "0". The deploy/images/machine directory can contain multiple kernel module tarballs for the
machine.
• bootloaders: Bootloaders supporting the image, if applicable to the target machine. The deploy/
images/machine directory can contain multiple bootloaders for the machine.
• symlinks: The deploy/images/machine folder contains a symbolic link that points to the most
recently built file for each machine. These links might be useful for external scripts that need to
obtain the latest version of each file.

3.7. Application Development SDK
In the general Yocto Project Development Environment figure[19], the output labeled "Application
Development SDK" represents an SDK. This section is going to take a closer look at this output:

The specific form of this output is a self-extracting SDK installer (*.sh) that, when run, installs
the SDK, which consists of a cross-development toolchain, a set of libraries and headers, and an
SDK environment setup script. Running this installer essentially sets up your cross-development
environment. You can think of the cross-toolchain as the "host" part because it runs on the SDK
machine. You can think of the libraries and headers as the "target" part because they are built for the
target hardware. The setup script is added so that you can initialize the environment before using
the tools.

Note
The Yocto Project supports several methods by which you can set up this cross-development
environment. These methods include downloading pre-built SDK installers, building and
installing your own SDK installer, or running an Application Development Toolkit (ADT)

37

A Closer Look at the Yocto Project Development Environment

installer to install not just cross-development toolchains but also additional tools to help in
this type of development.
For background information on cross-development toolchains in the Yocto Project
development environment, see the "Cross-Development Toolchain Generation" section.
For information on setting up a cross-development environment, see the
"Installing the ADT and Toolchains [http://www.yoctoproject.org/docs/1.8/adt-manual/adtmanual.html#installing-the-adt]" section in the Yocto Project Application Developer's Guide.
Once built, the SDK installers are written out to the deploy/sdk folder inside the Build Directory
[http://www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#build-directory] as shown in
the figure at the beginning of this section. Several variables exist that help configure these files:
• DEPLOY_DIR: Points to the deploy directory.
• SDKMACHINE: Specifies the architecture of the machine on which the cross-development tools are
run to create packages for the target hardware.
• SDKIMAGE_FEATURES: Lists the features to include in the "target" part of the SDK.
• TOOLCHAIN_HOST_TASK: Lists packages that make up the host part of the SDK (i.e. the part that
runs on the SDKMACHINE). When you use bitbake -c populate_sdk imagename to create the SDK,
a set of default packages apply. This variable allows you to add more packages.
• TOOLCHAIN_TARGET_TASK: Lists packages that make up the target part of the SDK (i.e. the part built
for the target hardware).
• SDKPATH: Defines the default SDK installation path offered by the installation script.

38

Chapter 4. Technical Details
This chapter provides technical details for various parts of the Yocto Project. Currently, topics include
Yocto Project components, cross-toolchain generation, shared state (sstate) cache, x32, Wayland
support, and Licenses.

4.1. Yocto Project Components
The BitBake [http://www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#bitbake-term] task
executor together with various types of configuration files form the OpenEmbedded Core. This section
overviews these components by describing their use and how they interact.
BitBake handles the parsing and execution of the data files. The data itself is of various types:
• Recipes: Provides details about particular pieces of software.
• Class Data: Abstracts common build information (e.g. how to build a Linux kernel).
• Configuration Data: Defines machine-specific settings, policy decisions, and so forth. Configuration
data acts as the glue to bind everything together.
BitBake
knows
how
to
combine
multiple
data
sources
together
and
refers
to
each
data
source
as
a
layer.
For
information
on
layers,
see
the
"Understanding and Creating Layers [http://www.yoctoproject.org/docs/1.8/dev-manual/devmanual.html#understanding-and-creating-layers]" section of the Yocto Project Development Manual.
Following are some brief details on these core components. For additional information on how
these components interact during a build, see the "A Closer Look at the Yocto Project Development
Environment" Chapter.

4.1.1. BitBake
BitBake is the tool at the heart of the OpenEmbedded build system and is
responsible for parsing the Metadata [http://www.yoctoproject.org/docs/1.8/dev-manual/devmanual.html#metadata], generating a list of tasks from it, and then executing those tasks.
This section briefly introduces BitBake. If you want more information on BitBake, see
the BitBake User Manual [http://www.yoctoproject.org/docs/1.8/bitbake-user-manual/bitbake-usermanual.html#bitbake-user-manual].
To see a list of the options BitBake supports, use either of the following commands:
$ bitbake -h
$ bitbake --help
The most common usage for BitBake is bitbake packagename, where packagename is the name of
the package you want to build (referred to as the "target" in this manual). The target often equates to
the first part of a recipe's filename (e.g. "foo" for a recipe named foo_1.3.0-r0.bb). So, to process
the matchbox-desktop_1.2.3.bb recipe file, you might type the following:
$ bitbake matchbox-desktop
Several different versions of matchbox-desktop might exist. BitBake chooses the one selected by
the distribution configuration. You can get more details about how BitBake chooses between different
target versions and providers in the "Preferences [http://www.yoctoproject.org/docs/1.8/bitbake-usermanual/bitbake-user-manual.html#bb-bitbake-preferences]" section of the BitBake User Manual.
BitBake also tries to execute any dependent tasks first. So for example, before building matchboxdesktop, BitBake would build a cross compiler and eglibc if they had not already been built.

39

Technical Details

Note
This release of the Yocto Project does not support the glibc GNU version of the Unix standard
C library. By default, the OpenEmbedded build system builds with eglibc.
A useful BitBake option to consider is the -k or --continue option. This option instructs BitBake to
try and continue processing the job as long as possible even after encountering an error. When an
error occurs, the target that failed and those that depend on it cannot be remade. However, when
you use this option other dependencies can still be processed.

4.1.2. Metadata (Recipes)
Files that have the .bb suffix are "recipes" files. In general, a recipe contains information about a
single piece of software. This information includes the location from which to download the unaltered
source, any source patches to be applied to that source (if needed), which special configuration
options to apply, how to compile the source files, and how to package the compiled output.
The term "package" is sometimes used to refer to recipes. However, since the word "package" is
used for the packaged output from the OpenEmbedded build system (i.e. .ipk or .deb files), this
document avoids using the term "package" when referring to recipes.

4.1.3. Classes
Class files (.bbclass) contain information that is useful to share between Metadata [http://
www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#metadata] files. An example is the
autotools class, which contains common settings for any application that Autotools uses. The
"Classes" chapter provides details about classes and how to use them.

4.1.4. Configuration
The configuration files (.conf) define various configuration variables that govern the OpenEmbedded
build process. These files fall into several areas that define machine configuration options,
distribution configuration options, compiler tuning options, general common configuration options,
and user configuration options in local.conf, which is found in the Build Directory [http://
www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#build-directory].

4.2. Cross-Development Toolchain Generation
The Yocto Project does most of the work for you when it comes to creating cross-development
toolchains [http://www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#cross-developmenttoolchain]. This section provides some technical background on how cross-development toolchains
are created and used. For more information on toolchains, you can also see the Yocto Project
Application Developer's Guide [http://www.yoctoproject.org/docs/1.8/adt-manual/adt-manual.html].
In the Yocto Project development environment, cross-development toolchains are used to build
the image and applications that run on the target hardware. With just a few commands, the
OpenEmbedded build system creates these necessary toolchains for you.
The following figure shows a high-level build environment regarding toolchain construction and use.

40

Technical Details

Most of the work occurs on the Build Host. This is the machine used to build images and generally
work within the the Yocto Project environment. When you run BitBake to create an image, the
OpenEmbedded build system uses the host gcc compiler to bootstrap a cross-compiler named gcccross. The gcc-cross compiler is what BitBake uses to compile source files when creating the target
image. You can think of gcc-cross simply as an automatically generated cross-compiler that is used
internally within BitBake only.
The chain of events that occurs when gcc-cross is bootstrapped is as follows:

gcc -> binutils-cross -> gcc-cross-initial -> linux-libc-headers -> eglibc-initial -> eglibc
• gcc: The build host's GNU Compiler Collection (GCC).
• binutils-cross: The bare minimum binary utilities needed in order to run the gcc-cross-initial
phase of the bootstrap operation.
• gcc-cross-initial: An early stage of the bootstrap process for creating the cross-compiler. This
stage builds enough of the gcc-cross, the C library, and other pieces needed to finish building
the final cross-compiler in later stages. This tool is a "native" package (i.e. it is designed to run
on the build host).
• linux-libc-headers: Headers needed for the cross-compiler.

41

Technical Details

• eglibc-initial: An initial version of the Embedded GLIBC needed to bootstrap eglibc.
• gcc-cross: The final stage of the bootstrap process for the cross-compiler. This stage results in the
actual cross-compiler that BitBake uses when it builds an image for a targeted device.

Note
If you are replacing this cross compiler toolchain with a custom version, you must replace
gcc-cross.
This tool is also a "native" package (i.e. it is designed to run on the build host).
• gcc-runtime: Runtime libraries resulting from the toolchain bootstrapping process. This tool
produces a binary that consists of the runtime libraries need for the targeted device.
You can use the OpenEmbedded build system to build an installer for the relocatable SDK used
to develop applications. When you run the installer, it installs the toolchain, which contains
the development tools (e.g., the gcc-cross-canadian), binutils-cross-canadian, and other
nativesdk-* tools you need to cross-compile and test your software. The figure shows the commands
you use to easily build out this toolchain. This cross-development toolchain is built to execute on the
SDKMACHINE, which might or might not be the same machine as the Build Host.

Note
If your target architecture is supported by the Yocto Project, you can take advantage of prebuilt images that ship with the Yocto Project and already contain cross-development toolchain
installers.
Here is the bootstrap process for the relocatable toolchain:
gcc -> binutils-crosssdk -> gcc-crosssdk-initial -> linux-libc-headers ->
eglibc-initial -> nativesdk-eglibc -> gcc-crosssdk -> gcc-cross-canadian
• gcc: The build host's GNU Compiler Collection (GCC).
• binutils-crosssdk: The bare minimum binary utilities needed in order to run the gcc-crosssdkinitial phase of the bootstrap operation.
• gcc-crosssdk-initial: An early stage of the bootstrap process for creating the cross-compiler.
This stage builds enough of the gcc-crosssdk and supporting pieces so that the final stage of the
bootstrap process can produce the finished cross-compiler. This tool is a "native" binary that runs
on the build host.
• linux-libc-headers: Headers needed for the cross-compiler.
• eglibc-initial: An initial version of the Embedded GLIBC needed to bootstrap nativesdkeglibc.
• nativesdk-eglibc: The Embedded GLIBC needed to bootstrap the gcc-crosssdk.
• gcc-crosssdk: The final stage of the bootstrap process for the relocatable cross-compiler. The
gcc-crosssdk is a transitory compiler and never leaves the build host. Its purpose is to help in
the bootstrap process to create the eventual relocatable gcc-cross-canadian compiler, which is
relocatable. This tool is also a "native" package (i.e. it is designed to run on the build host).
• gcc-cross-canadian: The final relocatable cross-compiler. When run on the SDKMACHINE, this tool
produces executable code that runs on the target device. Only one cross-canadian compiler is
produced per architecture since they can be targeted at different processor optimizations using
configurations passed to the compiler through the compile commands. This circumvents the need
for multiple compilers and thus reduces the size of the toolchains.

Note
For information on advantages gained when building a cross-development toolchain installer,
see the "Optionally Building a Toolchain Installer [http://www.yoctoproject.org/docs/1.8/
adt-manual/adt-manual.html#optionally-building-a-toolchain-installer]" section in the Yocto
Project Application Developer's Guide.

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4.3. Shared State Cache
By design, the OpenEmbedded build system builds everything from scratch unless BitBake can
determine that parts do not need to be rebuilt. Fundamentally, building from scratch is attractive
as it means all parts are built fresh and there is no possibility of stale data causing problems. When
developers hit problems, they typically default back to building from scratch so they know the state
of things from the start.
Building an image from scratch is both an advantage and a disadvantage to the process. As mentioned
in the previous paragraph, building from scratch ensures that everything is current and starts from a
known state. However, building from scratch also takes much longer as it generally means rebuilding
things that do not necessarily need to be rebuilt.
The Yocto Project implements shared state code that supports incremental builds. The implementation
of the shared state code answers the following questions that were fundamental roadblocks within
the OpenEmbedded incremental build support system:
• What pieces of the system have changed and what pieces have not changed?
• How are changed pieces of software removed and replaced?
• How are pre-built components that do not need to be rebuilt from scratch used when they are
available?
For the first question, the build system detects changes in the "inputs" to a given task by creating a
checksum (or signature) of the task's inputs. If the checksum changes, the system assumes the inputs
have changed and the task needs to be rerun. For the second question, the shared state (sstate) code
tracks which tasks add which output to the build process. This means the output from a given task
can be removed, upgraded or otherwise manipulated. The third question is partly addressed by the
solution for the second question assuming the build system can fetch the sstate objects from remote
locations and install them if they are deemed to be valid.

Note
The OpenEmbedded build system does not maintain PR information as part of the shared
state packages. Consequently, considerations exist that affect maintaining shared state
feeds. For information on how the OpenEmbedded build system works with packages
and can track incrementing PR information, see the "Incrementing a Package Revision
Number [http://www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#incrementinga-package-revision-number]" section.
The rest of this section goes into detail about the overall incremental build architecture, the
checksums (signatures), shared state, and some tips and tricks.

4.3.1. Overall Architecture
When determining what parts of the system need to be built, BitBake works on a per-task basis rather
than a per-recipe basis. You might wonder why using a per-task basis is preferred over a per-recipe
basis. To help explain, consider having the IPK packaging backend enabled and then switching to DEB.
In this case, the do_install and do_package task outputs are still valid. However, with a per-recipe
approach, the build would not include the .deb files. Consequently, you would have to invalidate the
whole build and rerun it. Rerunning everything is not the best solution. Also, in this case, the core must
be "taught" much about specific tasks. This methodology does not scale well and does not allow users
to easily add new tasks in layers or as external recipes without touching the packaged-staging core.

4.3.2. Checksums (Signatures)
The shared state code uses a checksum, which is a unique signature of a task's inputs, to determine
if a task needs to be run again. Because it is a change in a task's inputs that triggers a rerun, the
process needs to detect all the inputs to a given task. For shell tasks, this turns out to be fairly easy
because the build process generates a "run" shell script for each task and it is possible to create a
checksum that gives you a good idea of when the task's data changes.
To complicate the problem, there are things that should not be included in the checksum. First, there
is the actual specific build path of a given task - the WORKDIR. It does not matter if the work directory

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Technical Details

changes because it should not affect the output for target packages. Also, the build process has the
objective of making native or cross packages relocatable. The checksum therefore needs to exclude
WORKDIR. The simplistic approach for excluding the work directory is to set WORKDIR to some fixed
value and create the checksum for the "run" script.
Another problem results from the "run" scripts containing functions that might or might not get called.
The incremental build solution contains code that figures out dependencies between shell functions.
This code is used to prune the "run" scripts down to the minimum set, thereby alleviating this problem
and making the "run" scripts much more readable as a bonus.
So far we have solutions for shell scripts. What about Python tasks? The same approach applies
even though these tasks are more difficult. The process needs to figure out what variables a Python
function accesses and what functions it calls. Again, the incremental build solution contains code that
first figures out the variable and function dependencies, and then creates a checksum for the data
used as the input to the task.
Like the WORKDIR case, situations exist where dependencies should be ignored. For these cases, you
can instruct the build process to ignore a dependency by using a line like the following:
PACKAGE_ARCHS[vardepsexclude] = "MACHINE"
This example ensures that the PACKAGE_ARCHS variable does not depend on the value of MACHINE,
even if it does reference it.
Equally, there are cases where we need to add dependencies BitBake is not able to find. You can
accomplish this by using a line like the following:
PACKAGE_ARCHS[vardeps] = "MACHINE"
This example explicitly adds the MACHINE variable as a dependency for PACKAGE_ARCHS.
Consider a case with in-line Python, for example, where BitBake is not able to figure out dependencies.
When running in debug mode (i.e. using -DDD), BitBake produces output when it discovers something
for which it cannot figure out dependencies. The Yocto Project team has currently not managed to
cover those dependencies in detail and is aware of the need to fix this situation.
Thus far, this section has limited discussion to the direct inputs into a task. Information based
on direct inputs is referred to as the "basehash" in the code. However, there is still the question
of a task's indirect inputs - the things that were already built and present in the Build Directory
[http://www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#build-directory]. The checksum
(or signature) for a particular task needs to add the hashes of all the tasks on which the particular task
depends. Choosing which dependencies to add is a policy decision. However, the effect is to generate
a master checksum that combines the basehash and the hashes of the task's dependencies.
At the code level, there are a variety of ways both the basehash and the dependent task hashes can
be influenced. Within the BitBake configuration file, we can give BitBake some extra information to
help it construct the basehash. The following statement effectively results in a list of global variable
dependency excludes - variables never included in any checksum:
BB_HASHBASE_WHITELIST ?= "TMPDIR FILE PATH PWD BB_TASKHASH BBPATH DL_DIR \
SSTATE_DIR THISDIR FILESEXTRAPATHS FILE_DIRNAME HOME LOGNAME SHELL TERM \
USER FILESPATH STAGING_DIR_HOST STAGING_DIR_TARGET COREBASE PRSERV_HOST \
PRSERV_DUMPDIR PRSERV_DUMPFILE PRSERV_LOCKDOWN PARALLEL_MAKE \
CCACHE_DIR EXTERNAL_TOOLCHAIN CCACHE CCACHE_DISABLE LICENSE_PATH SDKPKGSUFFIX"
The previous example excludes WORKDIR since that variable is actually constructed as a path within
TMPDIR, which is on the whitelist.
The rules for deciding which hashes of dependent tasks to include through dependency chains are
more complex and are generally accomplished with a Python function. The code in meta/lib/oe/
sstatesig.py shows two examples of this and also illustrates how you can insert your own policy into

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the system if so desired. This file defines the two basic signature generators OE-Core uses: "OEBasic"
and "OEBasicHash". By default, there is a dummy "noop" signature handler enabled in BitBake. This
means that behavior is unchanged from previous versions. OE-Core uses the "OEBasicHash" signature
handler by default through this setting in the bitbake.conf file:
BB_SIGNATURE_HANDLER ?= "OEBasicHash"
The "OEBasicHash" BB_SIGNATURE_HANDLER is the same as the "OEBasic" version but adds the
task hash to the stamp files. This results in any Metadata [http://www.yoctoproject.org/docs/1.8/
dev-manual/dev-manual.html#metadata] change that changes the task hash, automatically causing
the task to be run again. This removes the need to bump PR values, and changes to Metadata
automatically ripple across the build.
It is also worth noting that the end result of these signature generators is to make some dependency
and hash information available to the build. This information includes:
• BB_BASEHASH_task-taskname: The base hashes for each task in the recipe.
• BB_BASEHASH_filename:taskname: The base hashes for each dependent task.
• BBHASHDEPS_filename:taskname: The task dependencies for each task.
• BB_TASKHASH: The hash of the currently running task.

4.3.3. Shared State
Checksums and dependencies, as discussed in the previous section, solve half the problem of
supporting a shared state. The other part of the problem is being able to use checksum information
during the build and being able to reuse or rebuild specific components.
The sstate class is a relatively generic implementation of how to "capture" a snapshot of a given
task. The idea is that the build process does not care about the source of a task's output. Output
could be freshly built or it could be downloaded and unpacked from somewhere - the build process
does not need to worry about its origin.
There are two types of output, one is just about creating a directory in WORKDIR. A good example is
the output of either do_install or do_package. The other type of output occurs when a set of data
is merged into a shared directory tree such as the sysroot.
The Yocto Project team has tried to keep the details of the implementation hidden in sstate class.
From a user's perspective, adding shared state wrapping to a task is as simple as this do_deploy
example taken from the deploy class:
DEPLOYDIR = "${WORKDIR}/deploy-${PN}"
SSTATETASKS += "do_deploy"
do_deploy[sstate-name] = "deploy"
do_deploy[sstate-inputdirs] = "${DEPLOYDIR}"
do_deploy[sstate-outputdirs] = "${DEPLOY_DIR_IMAGE}"
python do_deploy_setscene () {
sstate_setscene(d)
}
addtask do_deploy_setscene
do_deploy[dirs] = "${DEPLOYDIR} ${B}"
In this example, we add some extra flags to the task, a name field ("deploy"), an input directory where
the task sends data, and the output directory where the data from the task should eventually be
copied. We also add a _setscene variant of the task and add the task name to the SSTATETASKS list.
If you have a directory whose contents you need to preserve, you can do this with a line like the
following:

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do_package[sstate-plaindirs] = "${PKGD} ${PKGDEST}"
This method, as well as the following example, also works for multiple directories.
do_package[sstate-inputdirs] = "${PKGDESTWORK} ${SHLIBSWORKDIR}"
do_package[sstate-outputdirs] = "${PKGDATA_DIR} ${SHLIBSDIR}"
do_package[sstate-lockfile] = "${PACKAGELOCK}"
These methods also include the ability to take a lockfile when manipulating shared state directory
structures since some cases are sensitive to file additions or removals.
Behind the scenes, the shared state code works by looking in SSTATE_DIR and SSTATE_MIRRORS for
shared state files. Here is an example:
SSTATE_MIRRORS ?= "\
file://.* http://someserver.tld/share/sstate/PATH \n \
file://.* file:///some/local/dir/sstate/PATH"

Note
The shared state directory (SSTATE_DIR) is organized into two-character subdirectories,
where the subdirectory names are based on the first two characters of the hash. If the shared
state directory structure for a mirror has the same structure as SSTATE_DIR, you must specify
"PATH" as part of the URI to enable the build system to map to the appropriate subdirectory.
The shared state package validity can be detected just by looking at the filename since the filename
contains the task checksum (or signature) as described earlier in this section. If a valid shared state
package is found, the build process downloads it and uses it to accelerate the task.
The build processes use the *_setscene tasks for the task acceleration phase. BitBake goes through
this phase before the main execution code and tries to accelerate any tasks for which it can find
shared state packages. If a shared state package for a task is available, the shared state package is
used. This means the task and any tasks on which it is dependent are not executed.
As a real world example, the aim is when building an IPK-based image, only the
do_package_write_ipk tasks would have their shared state packages fetched and extracted. Since
the sysroot is not used, it would never get extracted. This is another reason why a task-based
approach is preferred over a recipe-based approach, which would have to install the output from
every task.

4.3.4. Tips and Tricks
The code in the build system that supports incremental builds is not simple code. This section presents
some tips and tricks that help you work around issues related to shared state code.

4.3.4.1. Debugging
When things go wrong, debugging needs to be straightforward. Because of this, the Yocto Project
includes strong debugging tools:
• Whenever a shared state package is written out, so is a corresponding .siginfo file. This practice
results in a pickled Python database of all the metadata that went into creating the hash for a given
shared state package.
• If you run BitBake with the --dump-signatures (or -S) option, BitBake dumps out .siginfo files in
the stamp directory for every task it would have executed instead of building the specified target
package.
• There is a bitbake-diffsigs command that can process .siginfo files. If you specify one of these
files, BitBake dumps out the dependency information in the file. If you specify two files, BitBake
compares the two files and dumps out the differences between the two. This more easily helps
answer the question of "What changed between X and Y?"

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4.3.4.2. Invalidating Shared State
The OpenEmbedded build system uses checksums and shared state cache to avoid unnecessarily
rebuilding tasks. Collectively, this scheme is known as "shared state code."
As with all schemes, this one has some drawbacks. It is possible that you could make implicit changes
to your code that the checksum calculations do not take into account. These implicit changes affect
a task's output but do not trigger the shared state code into rebuilding a recipe. Consider an example
during which a tool changes its output. Assume that the output of rpmdeps changes. The result of the
change should be that all the package and package_write_rpm shared state cache items become
invalid. However, because the change to the output is external to the code and therefore implicit,
the associated shared state cache items do not become invalidated. In this case, the build process
uses the cached items rather than running the task again. Obviously, these types of implicit changes
can cause problems.
To avoid these problems during the build, you need to understand the effects of any changes you
make. Realize that changes you make directly to a function are automatically factored into the
checksum calculation. Thus, these explicit changes invalidate the associated area of shared state
cache. However, you need to be aware of any implicit changes that are not obvious changes to the
code and could affect the output of a given task.
When you identify an implicit change, you can easily take steps to invalidate the cache and force
the tasks to run. The steps you can take are as simple as changing a function's comments in the
source code. For example, to invalidate package shared state files, change the comment statements
of do_package or the comments of one of the functions it calls. Even though the change is purely
cosmetic, it causes the checksum to be recalculated and forces the OpenEmbedded build system to
run the task again.

Note
For an example of a commit that makes a cosmetic change to invalidate shared state, see
this commit [http://git.yoctoproject.org/cgit.cgi/poky/commit/meta/classes/package.bbclass?
id=737f8bbb4f27b4837047cb9b4fbfe01dfde36d54].

4.4. x32
x32 is a processor-specific Application Binary Interface (psABI) for x86_64. An ABI defines the calling
conventions between functions in a processing environment. The interface determines what registers
are used and what the sizes are for various C data types.
Some processing environments prefer using 32-bit applications even when running on Intel 64-bit
platforms. Consider the i386 psABI, which is a very old 32-bit ABI for Intel 64-bit platforms. The i386
psABI does not provide efficient use and access of the Intel 64-bit processor resources, leaving the
system underutilized. Now consider the x86_64 psABI. This ABI is newer and uses 64-bits for data sizes
and program pointers. The extra bits increase the footprint size of the programs, libraries, and also
increases the memory and file system size requirements. Executing under the x32 psABI enables user
programs to utilize CPU and system resources more efficiently while keeping the memory footprint
of the applications low. Extra bits are used for registers but not for addressing mechanisms.

4.4.1. Support
This Yocto Project release supports the final specifications of x32 psABI. Support for x32 psABI exists
as follows:
• You can create packages and images in x32 psABI format on x86_64 architecture targets.
• You can successfully build many recipes with the x32 toolchain.
• You can create and boot core-image-minimal and core-image-sato images.

4.4.2. Completing x32
Future Plans for the x32 psABI in the Yocto Project include the following:
• Enhance and fix the few remaining recipes so they work with and support x32 toolchains.

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• Enhance RPM Package Manager (RPM) support for x32 binaries.
• Support larger images.

4.4.3. Using x32 Right Now
Follow these steps to use the x32 spABI:
• Enable the x32 psABI tuning file for x86_64 machines by editing the conf/local.conf like this:
MACHINE = "qemux86-64"
DEFAULTTUNE = "x86-64-x32"
baselib = "${@d.getVar('BASE_LIB_tune-' + (d.getVar('DEFAULTTUNE', True) \
or 'INVALID'), True) or 'lib'}"
#MACHINE = "genericx86"
#DEFAULTTUNE = "core2-64-x32"
• As usual, use BitBake to build an image that supports the x32 psABI. Here is an example:
$ bitbake core-image-sato
• As usual, run your image using QEMU:
$ runqemu qemux86-64 core-image-sato

4.5. Wayland
Wayland [http://en.wikipedia.org/wiki/Wayland_(display_server_protocol)] is a computer display
server protocol that provides a method for compositing window managers to communicate directly
with applications and video hardware and expects them to communicate with input hardware using
other libraries. Using Wayland with supporting targets can result in better control over graphics frame
rendering than an application might otherwise achieve.
The Yocto Project provides the Wayland protocol libraries and the reference Weston [http://
en.wikipedia.org/wiki/Wayland_(display_server_protocol)#Weston] compositor as part of its release.
This section describes what you need to do to implement Wayland and use the compositor when
building an image for a supporting target.

4.5.1. Support
The Wayland protocol libraries and the reference Weston compositor ship as integrated packages
in the meta layer of the Source Directory [http://www.yoctoproject.org/docs/1.8/dev-manual/devmanual.html#source-directory]. Specifically, you can find the recipes that build both Wayland and
Weston at meta/recipes-graphics/wayland.
You can build both the Wayland and Weston packages for use only with targets that accept the Mesa
3D and Direct Rendering Infrastructure [http://dri.freedesktop.org/wiki/], which is also known as Mesa
DRI. This implies that you cannot build and use the packages if your target uses, for example, the
Intel® Embedded Media and Graphics Driver (Intel® EMGD) that overrides Mesa DRI.

Note
Due to lack of EGL support, Weston 1.0.3 will not run directly on the emulated QEMU hardware.
However, this version of Weston will run under X emulation without issues.

4.5.2. Enabling Wayland in an Image
To enable Wayland, you need to enable it to be built and enable it to be included in the image.

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4.5.2.1. Building
To cause Mesa to build the wayland-egl platform and Weston to build Wayland with Kernel
Mode Setting (KMS [https://wiki.archlinux.org/index.php/Kernel_Mode_Setting]) support, include the
"wayland" flag in the DISTRO_FEATURES statement in your local.conf file:
DISTRO_FEATURES_append = " wayland"

Note
If X11 has been enabled elsewhere, Weston will build Wayland with X11 support

4.5.2.2. Installing
To install the Wayland feature into an image, you
CORE_IMAGE_EXTRA_INSTALL statement in your local.conf file:

must

include

the

following

CORE_IMAGE_EXTRA_INSTALL += "wayland weston"

4.5.3. Running Weston
To run Weston inside X11, enabling it as described earlier and building a Sato image is sufficient. If
you are running your image under Sato, a Weston Launcher appears in the "Utility" category.
Alternatively, you can run Weston through the command-line interpretor (CLI), which is better suited
for development work. To run Weston under the CLI, you need to do the following after your image
is built:
1. Run these commands to export XDG_RUNTIME_DIR:
mkdir -p /tmp/$USER-weston
chmod 0700 /tmp/$USER-weston
export XDG_RUNTIME_DIR=/tmp/$USER-weston
2. Launch Weston in the shell:
weston

4.6. Licenses
This section describes the mechanism by which the OpenEmbedded build system tracks changes
to licensing text. The section also describes how to enable commercially licensed recipes, which by
default are disabled.
For information that can help you maintain compliance with various open source
licensing during the lifecycle of the product, see the "Maintaining Open Source License
Compliance During Your Project's Lifecycle [http://www.yoctoproject.org/docs/1.8/dev-manual/devmanual.html#maintaining-open-source-license-compliance-during-your-products-lifecycle]" section
in the Yocto Project Development Manual.

4.6.1. Tracking License Changes
The license of an upstream project might change in the future. In order to prevent these changes
going unnoticed, the LIC_FILES_CHKSUM variable tracks changes to the license text. The checksums
are validated at the end of the configure step, and if the checksums do not match, the build will fail.

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4.6.1.1. Specifying theLIC_FILES_CHKSUM Variable
The LIC_FILES_CHKSUM variable contains checksums of the license text in the source code for the
recipe. Following is an example of how to specify LIC_FILES_CHKSUM:
LIC_FILES_CHKSUM = "file://COPYING;md5=xxxx \
file://licfile1.txt;beginline=5;endline=29;md5=yyyy \
file://licfile2.txt;endline=50;md5=zzzz \
..."
The build system uses the S variable as the default directory when searching files listed in
LIC_FILES_CHKSUM. The previous example employs the default directory.
Consider this next example:
LIC_FILES_CHKSUM = "file://src/ls.c;beginline=5;endline=16;\
md5=bb14ed3c4cda583abc85401304b5cd4e"
LIC_FILES_CHKSUM = "file://${WORKDIR}/license.html;md5=5c94767cedb5d6987c902ac850ded2c6"
The first line locates a file in ${S}/src/ls.c. The second line refers to a file in WORKDIR.
Note that LIC_FILES_CHKSUM variable is mandatory for all recipes, unless the LICENSE variable is
set to "CLOSED".

4.6.1.2. Explanation of Syntax
As mentioned in the previous section, the LIC_FILES_CHKSUM variable lists all the important files that
contain the license text for the source code. It is possible to specify a checksum for an entire file, or
a specific section of a file (specified by beginning and ending line numbers with the "beginline" and
"endline" parameters, respectively). The latter is useful for source files with a license notice header,
README documents, and so forth. If you do not use the "beginline" parameter, then it is assumed
that the text begins on the first line of the file. Similarly, if you do not use the "endline" parameter,
it is assumed that the license text ends with the last line of the file.
The "md5" parameter stores the md5 checksum of the license text. If the license text changes in any
way as compared to this parameter then a mismatch occurs. This mismatch triggers a build failure
and notifies the developer. Notification allows the developer to review and address the license text
changes. Also note that if a mismatch occurs during the build, the correct md5 checksum is placed
in the build log and can be easily copied to the recipe.
There is no limit to how many files you can specify using the LIC_FILES_CHKSUM variable. Generally,
however, every project requires a few specifications for license tracking. Many projects have a
"COPYING" file that stores the license information for all the source code files. This practice allows
you to just track the "COPYING" file as long as it is kept up to date.

Tip
If you specify an empty or invalid "md5" parameter, BitBake returns an md5 mis-match error
and displays the correct "md5" parameter value during the build. The correct parameter is
also captured in the build log.

Tip
If the whole file contains only license text, you do not need to use the "beginline" and "endline"
parameters.

4.6.2. Enabling Commercially Licensed Recipes
By default, the OpenEmbedded build system disables components that have commercial or other
special licensing requirements. Such requirements are defined on a recipe-by-recipe basis through
the LICENSE_FLAGS variable definition in the affected recipe. For instance, the poky/meta/recipesmultimedia/gstreamer/gst-plugins-ugly recipe contains the following statement:

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LICENSE_FLAGS = "commercial"
Here is a slightly more complicated example that contains both an explicit recipe name and version
(after variable expansion):
LICENSE_FLAGS = "license_${PN}_${PV}"
In order for a component restricted by a LICENSE_FLAGS definition to be enabled and included
in an image, it needs to have a matching entry in the global LICENSE_FLAGS_WHITELIST
variable, which is a variable typically defined in your local.conf file. For example, to
enable the poky/meta/recipes-multimedia/gstreamer/gst-plugins-ugly package, you could
add either the string "commercial_gst-plugins-ugly" or the more general string "commercial" to
LICENSE_FLAGS_WHITELIST. See the "License Flag Matching" section for a full explanation of how
LICENSE_FLAGS matching works. Here is the example:
LICENSE_FLAGS_WHITELIST = "commercial_gst-plugins-ugly"
Likewise, to additionally enable the package built from the recipe containing LICENSE_FLAGS
= "license_${PN}_${PV}", and assuming that the actual recipe name was emgd_1.10.bb, the
following string would enable that package as well as the original gst-plugins-ugly package:
LICENSE_FLAGS_WHITELIST = "commercial_gst-plugins-ugly license_emgd_1.10"
As a convenience, you do not need to specify the complete license string in the whitelist for every
package. You can use an abbreviated form, which consists of just the first portion or portions of the
license string before the initial underscore character or characters. A partial string will match any
license that contains the given string as the first portion of its license. For example, the following
whitelist string will also match both of the packages previously mentioned as well as any other
packages that have licenses starting with "commercial" or "license".
LICENSE_FLAGS_WHITELIST = "commercial license"

4.6.2.1. License Flag Matching
License flag matching allows you to control what recipes the OpenEmbedded build system includes in
the build. Fundamentally, the build system attempts to match LICENSE_FLAGS strings found in recipes
against LICENSE_FLAGS_WHITELIST strings found in the whitelist. A match causes the build system to
include a recipe in the build, while failure to find a match causes the build system to exclude a recipe.
In general, license flag matching is simple. However, understanding some concepts will help you
correctly and effectively use matching.
Before a flag defined by a particular recipe is tested against the contents of the whitelist, the
expanded string _${PN} is appended to the flag. This expansion makes each LICENSE_FLAGS value
recipe-specific. After expansion, the string is then matched against the whitelist. Thus, specifying
LICENSE_FLAGS = "commercial" in recipe "foo", for example, results in the string "commercial_foo".
And, to create a match, that string must appear in the whitelist.
Judicious use of the LICENSE_FLAGS strings and the contents of the LICENSE_FLAGS_WHITELIST
variable allows you a lot of flexibility for including or excluding recipes based on licensing. For
example, you can broaden the matching capabilities by using license flags string subsets in the
whitelist.

Note
When using a string subset, be sure to use the part of the expanded string that precedes the
appended underscore character (e.g. usethispart_1.3, usethispart_1.4, and so forth).

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Technical Details

For example, simply specifying the string "commercial" in the whitelist matches any expanded
LICENSE_FLAGS definition that starts with the string "commercial" such as "commercial_foo" and
"commercial_bar", which are the strings the build system automatically generates for hypothetical
recipes named "foo" and "bar" assuming those recipes simply specify the following:
LICENSE_FLAGS = "commercial"
Thus, you can choose to exhaustively enumerate each license flag in the whitelist and allow only
specific recipes into the image, or you can use a string subset that causes a broader range of matches
to allow a range of recipes into the image.
This scheme works even if the LICENSE_FLAGS string already has _${PN} appended. For example, the
build system turns the license flag "commercial_1.2_foo" into "commercial_1.2_foo_foo" and would
match both the general "commercial" and the specific "commercial_1.2_foo" strings found in the
whitelist, as expected.
Here are some other scenarios:
• You can specify a versioned string in the recipe such as "commercial_foo_1.2" in a "foo" recipe.
The build system expands this string to "commercial_foo_1.2_foo". Combine this license flag with
a whitelist that has the string "commercial" and you match the flag along with any other flag that
starts with the string "commercial".
• Under the same circumstances, you can use "commercial_foo" in the whitelist and the build
system not only matches "commercial_foo_1.2" but also matches any license flag with the string
"commercial_foo", regardless of the version.
• You can be very specific and use both the package and version parts in the whitelist (e.g.
"commercial_foo_1.2") to specifically match a versioned recipe.

4.6.2.2. Other Variables Related to Commercial Licenses
Other helpful variables related to commercial license handling exist and are defined in the poky/
meta/conf/distro/include/default-distrovars.inc file:
COMMERCIAL_AUDIO_PLUGINS ?= ""
COMMERCIAL_VIDEO_PLUGINS ?= ""
COMMERCIAL_QT = ""
If you want to enable these components, you can do so by making sure you have statements similar
to the following in your local.conf configuration file:

COMMERCIAL_AUDIO_PLUGINS = "gst-plugins-ugly-mad \
gst-plugins-ugly-mpegaudioparse"
COMMERCIAL_VIDEO_PLUGINS = "gst-plugins-ugly-mpeg2dec \
gst-plugins-ugly-mpegstream gst-plugins-bad-mpegvideoparse"
COMMERCIAL_QT ?= "qmmp"
LICENSE_FLAGS_WHITELIST = "commercial_gst-plugins-ugly commercial_gst-plugins-bad commercial
Of course, you could also create a matching whitelist for those components using the more general
"commercial" in the whitelist, but that would also enable all the other packages with LICENSE_FLAGS
containing "commercial", which you may or may not want:
LICENSE_FLAGS_WHITELIST = "commercial"
Specifying audio and video plug-ins as part of the COMMERCIAL_AUDIO_PLUGINS and
COMMERCIAL_VIDEO_PLUGINS statements or commercial Qt components as part of the COMMERCIAL_QT
statement (along with the enabling LICENSE_FLAGS_WHITELIST) includes the plug-ins or components
into built images, thus adding support for media formats or components.

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Chapter 5. Migrating to a Newer
Yocto Project Release
This chapter provides information you can use to migrate work to a newer Yocto Project release. You
can find the same information in the release notes for a given release.

5.1. General Migration Considerations
Some considerations are not tied to a specific Yocto Project release. This section presents information
you should consider when migrating to any new Yocto Project release.
• Dealing with Customized Recipes: Issues could arise if you take older recipes that contain
customizations and simply copy them forward expecting them to work after you migrate to new
Yocto Project metadata. For example, suppose you have a recipe in your layer that is a customized
version of a core recipe copied from the earlier release, rather than through the use of an append
file. When you migrate to a newer version of Yocto Project, the metadata (e.g. perhaps an include
file used by the recipe) could have changed in a way that would break the build. Say, for example,
a function is removed from an include file and the customized recipe tries to call that function.
You could "forward-port" all your customizations in your recipe so that everything works for the new
release. However, this is not the optimal solution as you would have to repeat this process with
each new release if changes occur that give rise to problems.
The better solution (where practical) is to use append files (*.bbappend) to capture any
customizations you want to make to a recipe. Doing so, isolates your changes from the main recipe
making them much more manageable. However, sometimes it is not practical to use an append
file. A good example of this is when introducing a newer or older version of a recipe in another layer.
• Updating Append Files: Since append files generally only contain your customizations, they often
do not need to be adjusted for new releases. However, if the .bbappend file is specific to a particular
version of the recipe (i.e. its name does not use the % wildcard) and the version of the recipe to
which it is appending has changed, then you will at a minimum need to rename the append file to
match the name of the recipe file. A mismatch between an append file and its corresponding recipe
file (.bb) will trigger an error during parsing.
Depending on the type of customization the append file applies, other incompatibilities might occur
when you upgrade. For example, if your append file applies a patch and the recipe to which it is
appending is updated to a newer version, the patch might no longer apply. If this is the case and
assuming the patch is still needed, you must modify the patch file so that it does apply.

5.2. Moving to the Yocto Project 1.3 Release
This section provides migration information for moving to the Yocto Project 1.3 Release from the prior
release.

5.2.1. Local Configuration
Differences include changes for SSTATE_MIRRORS and bblayers.conf.

5.2.1.1. SSTATE_MIRRORS
The shared state cache (sstate-cache), as pointed to by SSTATE_DIR, by default now has twocharacter subdirectories to prevent issues arising from too many files in the same directory. Also,
native sstate-cache packages will go into a subdirectory named using the distro ID string. If you copy
the newly structured sstate-cache to a mirror location (either local or remote) and then point to it
in SSTATE_MIRRORS, you need to append "PATH" to the end of the mirror URL so that the path used
by BitBake before the mirror substitution is appended to the path used to access the mirror. Here
is an example:

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Migrating to a Newer Yocto Project Release

SSTATE_MIRRORS = "file://.* http://someserver.tld/share/sstate/PATH"

5.2.1.2. bblayers.conf
The meta-yocto layer consists of two parts that correspond to the Poky reference distribution and the
reference hardware Board Support Packages (BSPs), respectively: meta-yocto and meta-yocto-bsp.
When running BitBake or Hob for the first time after upgrading, your conf/bblayers.conf file will be
updated to handle this change and you will be asked to re-run or restart for the changes to take effect.

5.2.2. Recipes
Differences include changes for the following:
• Python function whitespace
• proto= in SRC_URI
• nativesdk
• Task recipes
• IMAGE_FEATURES
• Removed recipes

5.2.2.1. Python Function Whitespace
All Python functions must now use four spaces for indentation. Previously, an inconsistent mix
of spaces and tabs existed, which made extending these functions using _append or _prepend
complicated given that Python treats whitespace as syntactically significant. If you are defining or
extending any Python functions (e.g. populate_packages, do_unpack, do_patch and so forth) in
custom recipes or classes, you need to ensure you are using consistent four-space indentation.

5.2.2.2. proto= in SRC_URI
Any use of proto= in SRC_URI needs to be changed to protocol=. In particular, this applies to the
following URIs:
• svn://
• bzr://
• hg://
• osc://
Other URIs were already using protocol=. This change improves consistency.

5.2.2.3. nativesdk
The suffix nativesdk is now implemented as a prefix, which simplifies a lot of the packaging code
for nativesdk recipes. All custom nativesdk recipes and any references need to be updated to use
nativesdk-* instead of *-nativesdk.

5.2.2.4. Task Recipes
"Task" recipes are now known as "Package groups" and have been renamed from task-*.bb to
packagegroup-*.bb. Existing references to the previous task-* names should work in most cases as
there is an automatic upgrade path for most packages. However, you should update references in your
own recipes and configurations as they could be removed in future releases. You should also rename
any custom task-* recipes to packagegroup-*, and change them to inherit packagegroup instead of
task, as well as taking the opportunity to remove anything now handled by packagegroup.bbclass,
such as providing -dev and -dbg packages, setting LIC_FILES_CHKSUM, and so forth. See the
"packagegroup.bbclass" section for further details.

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Migrating to a Newer Yocto Project Release

5.2.2.5. IMAGE_FEATURES
Image recipes that previously included "apps-console-core" in IMAGE_FEATURES should now include
"splash" instead to enable the boot-up splash screen. Retaining "apps-console-core" will still
include the splash screen but generates a warning. The "apps-x11-core" and "apps-x11-games"
IMAGE_FEATURES features have been removed.

5.2.2.6. Removed Recipes
The following recipes have been removed. For most of them, it is unlikely that you would have
any references to them in your own Metadata [http://www.yoctoproject.org/docs/1.8/dev-manual/devmanual.html#metadata]. However, you should check your metadata against this list to be sure:
• libx11-trim: Replaced by libx11, which has a negligible size difference with modern Xorg.
• xserver-xorg-lite: Use xserver-xorg, which has a negligible size difference when DRI and GLX
modules are not installed.
• xserver-kdrive: Effectively unmaintained for many years.
• mesa-xlib: No longer serves any purpose.
• galago: Replaced by telepathy.
• gail: Functionality was integrated into GTK+ 2.13.
• eggdbus: No longer needed.
• gcc-*-intermediate: The build has been restructured to avoid the need for this step.
• libgsmd: Unmaintained for many years. Functionality now provided by ofono instead.
• contacts, dates, tasks, eds-tools: Largely unmaintained PIM application suite. It has been moved
to meta-gnome in meta-openembedded.
In addition to the previously listed changes, the meta-demoapps directory has also been removed
because the recipes in it were not being maintained and many had become obsolete or broken.
Additionally, these recipes were not parsed in the default configuration. Many of these recipes are
already provided in an updated and maintained form within the OpenEmbedded community layers
such as meta-oe and meta-gnome. For the remainder, you can now find them in the meta-extras
repository, which is in the Yocto Project Source Repositories [http://www.yoctoproject.org/docs/1.8/
dev-manual/dev-manual.html#source-repositories].

5.2.3. Linux Kernel Naming
The naming scheme for kernel output binaries has been changed to now include PE as part of the
filename:
KERNEL_IMAGE_BASE_NAME ?= "${KERNEL_IMAGETYPE}-${PE}-${PV}-${PR}-${MACHINE}-${DATETIME}"
Because the PE variable is not set by default, these binary files could result with names that include
two dash characters. Here is an example:
bzImage--3.10.9+git0+cd502a8814_7144bcc4b8-r0-qemux86-64-20130830085431.bin

5.3. Moving to the Yocto Project 1.4 Release
This section provides migration information for moving to the Yocto Project 1.4 Release from the prior
release.

5.3.1. BitBake
Differences include the following:

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Migrating to a Newer Yocto Project Release

• Comment Continuation: If a comment ends with a line continuation (\) character, then the next line
must also be a comment. Any instance where this is not the case, now triggers a warning. You must
either remove the continuation character, or be sure the next line is a comment.
• Package Name Overrides: The runtime package specific variables RDEPENDS, RRECOMMENDS,
RSUGGESTS, RPROVIDES, RCONFLICTS, RREPLACES, FILES, ALLOW_EMPTY, and the pre, post, install,
and uninstall script functions pkg_preinst, pkg_postinst, pkg_prerm, and pkg_postrm should
always have a package name override. For example, use RDEPENDS_${PN} for the main package
instead of RDEPENDS. BitBake uses more strict checks when it parses recipes.

5.3.2. Build Behavior
Differences include the following:
• Shared State Code: The shared state code has been optimized to avoid running unnecessary tasks.
For example, the following no longer populates the target sysroot since that is not necessary:
$ bitbake -c rootfs some-image
Instead, the system just needs to extract the output package contents, re-create the packages,
and construct the root filesystem. This change is unlikely to cause any problems unless you have
missing declared dependencies.
• Scanning Directory Names: When scanning for files in SRC_URI, the build system now uses
FILESOVERRIDES instead of OVERRIDES for the directory names. In general, the values previously in
OVERRIDES are now in FILESOVERRIDES as well. However, if you relied upon an additional value you
previously added to OVERRIDES, you might now need to add it to FILESOVERRIDES unless you are
already adding it through the MACHINEOVERRIDES or DISTROOVERRIDES variables, as appropriate.
For more related changes, see the "Variables" section.

5.3.3. Proxies and Fetching Source
A new oe-git-proxy script has been added to replace previous methods of handling proxies and
fetching source from Git. See the meta-yocto/conf/site.conf.sample file for information on how
to use this script.

5.3.4. Custom Interfaces File (netbase change)
If you have created your own custom etc/network/interfaces file by creating an append file for
the netbase recipe, you now need to create an append file for the init-ifupdown recipe instead,
which you can find in the Source Directory [http://www.yoctoproject.org/docs/1.8/dev-manual/devmanual.html#source-directory] at meta/recipes-core/init-ifupdown. For information on how to
use append files, see the "Using .bbappend Files [http://www.yoctoproject.org/docs/1.8/dev-manual/
dev-manual.html#using-bbappend-files]" in the Yocto Project Development Manual.

5.3.5. Remote Debugging
Support for remote debugging with the Eclipse IDE is now separated into an image feature (eclipsedebug) that corresponds to the packagegroup-core-eclipse-debug package group. Previously, the
debugging feature was included through the tools-debug image feature, which corresponds to the
packagegroup-core-tools-debug package group.

5.3.6. Variables
The following variables have changed:
• SANITY_TESTED_DISTROS: This variable now uses a distribution ID, which is composed of the host
distributor ID followed by the release. Previously, SANITY_TESTED_DISTROS was composed of the
description field. For example, "Ubuntu 12.10" becomes "Ubuntu-12.10". You do not need to worry
about this change if you are not specifically setting this variable, or if you are specifically setting
it to "".

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Migrating to a Newer Yocto Project Release

• SRC_URI: The ${PN}, ${PF}, ${P}, and FILE_DIRNAME directories have been dropped from the
default value of the FILESPATH variable, which is used as the search path for finding files referred
to in SRC_URI. If you have a recipe that relied upon these directories, which would be unusual, then
you will need to add the appropriate paths within the recipe or, alternatively, rearrange the files.
The most common locations are still covered by ${BP}, ${BPN}, and "files", which all remain in the
default value of FILESPATH.

5.3.7. Target Package Management with RPM
If runtime package management is enabled and the RPM backend is selected, Smart is now installed
for package download, dependency resolution, and upgrades instead of Zypper. For more information
on how to use Smart, run the following command on the target:
smart --help

5.3.8. Recipes Moved
The following recipes were moved from their previous locations because they are no longer used by
anything in the OpenEmbedded-Core:
• clutter-box2d: Now resides in the meta-oe layer.
• evolution-data-server: Now resides in the meta-gnome layer.
• gthumb: Now resides in the meta-gnome layer.
• gtkhtml2: Now resides in the meta-oe layer.
• gupnp: Now resides in the meta-multimedia layer.
• gypsy: Now resides in the meta-oe layer.
• libcanberra: Now resides in the meta-gnome layer.
• libgdata: Now resides in the meta-gnome layer.
• libmusicbrainz: Now resides in the meta-multimedia layer.
• metacity: Now resides in the meta-gnome layer.
• polkit: Now resides in the meta-oe layer.
• zeroconf: Now resides in the meta-networking layer.

5.3.9. Removals and Renames
The following list shows what has been removed or renamed:
• evieext: Removed because it has been removed from xserver since 2008.
• Gtk+ DirectFB: Removed support because upstream Gtk+ no longer supports it as of version 2.18.
• libxfontcache / xfontcacheproto: Removed because they were removed from the Xorg server
in 2008.
• libxp / libxprintapputil / libxprintutil / printproto: Removed because the XPrint server
was removed from Xorg in 2008.
• libxtrap / xtrapproto: Removed because their functionality was broken upstream.
• linux-yocto 3.0 kernel: Removed with linux-yocto 3.8 kernel being added. The linux-yocto 3.2 and
linux-yocto 3.4 kernels remain as part of the release.
• lsbsetup: Removed with functionality now provided by lsbtest.
• matchbox-stroke: Removed because it was never more than a proof-of-concept.

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Migrating to a Newer Yocto Project Release

• matchbox-wm-2 / matchbox-theme-sato-2: Removed because they are not maintained. However,
matchbox-wm and matchbox-theme-sato are still provided.
• mesa-dri: Renamed to mesa.
• mesa-xlib: Removed because it was no longer useful.
• mutter: Removed because nothing ever uses it and the recipe is very old.
• orinoco-conf: Removed because it has become obsolete.
• update-modules: Removed because it is no longer used. The kernel module postinstall and
postrm scripts can now do the same task without the use of this script.
• web: Removed because it is not maintained. Superseded by web-webkit.
• xf86bigfontproto: Removed because upstream it has been disabled by default since 2007.
Nothing uses xf86bigfontproto.
• xf86rushproto: Removed because its dependency in xserver was spurious and it was removed
in 2005.
• zypper / libzypp / sat-solver: Removed and been functionally replaced with Smart (pythonsmartpm) when RPM packaging is used and package management is enabled on the target.

5.4. Moving to the Yocto Project 1.5 Release
This section provides migration information for moving to the Yocto Project 1.5 Release from the prior
release.

5.4.1. Host Dependency Changes
The OpenEmbedded build system now has some additional requirements on the host system:
• Python 2.7.3+
• Tar 1.24+
• Git 1.7.8+
• Patched version of Make if you are using 3.82. Most distributions that provide Make 3.82 use the
patched version.
If the Linux distribution you are using on your build host does not provide packages for these, you
can install and use the Buildtools tarball, which provides an SDK-like environment containing them.
For more information on this requirement, see the "Required Git, tar, and Python Versions" section.

5.4.2. atom-pc Board Support Package (BSP)
The atom-pc hardware reference BSP has been replaced by a genericx86 BSP. This BSP is not
necessarily guaranteed to work on all x86 hardware, but it will run on a wider range of systems than
the atom-pc did.

Note
Additionally, a genericx86-64 BSP has been added for 64-bit Atom systems.

5.4.3. BitBake
The following changes have been made that relate to BitBake:
• BitBake now supports a _remove operator. The addition of this operator means you will have to
rename any items in recipe space (functions, variables) whose names currently contain _remove_
or end with _remove to avoid unexpected behavior.
• BitBake's global method pool has been removed. This method is not particularly useful and led to
clashes between recipes containing functions that had the same name.

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• The "none" server backend has been removed. The "process" server backend has been serving well
as the default for a long time now.
• The bitbake-runtask script has been removed.
• ${P} and ${PF} are no longer added to PROVIDES by default in bitbake.conf. These versionspecific PROVIDES items were seldom used. Attempting to use them could result in two versions
being built simultaneously rather than just one version due to the way BitBake resolves
dependencies.

5.4.4. QA Warnings
The following changes have been made to the package QA checks:
• If you have customized ERROR_QA or WARN_QA values in your configuration, check that they contain
all of the issues that you wish to be reported. Previous Yocto Project versions contained a bug
that meant that any item not mentioned in ERROR_QA or WARN_QA would be treated as a warning.
Consequently, several important items were not already in the default value of WARN_QA. All of the
possible QA checks are now documented in the "insane.bbclass" section.
• An additional QA check has been added to check if /usr/share/info/dir is being installed. Your
recipe should delete this file within do_install if "make install" is installing it.
• If you are using the buildhistory class, the check for the package version going backwards is now
controlled using a standard QA check. Thus, if you have customized your ERROR_QA or WARN_QA
values and still wish to have this check performed, you should add "version-going-backwards" to
your value for one or the other variables depending on how you wish it to be handled. See the
documented QA checks in the "insane.bbclass" section.

5.4.5. Directory Layout Changes
The following directory changes exist:
• Output SDK installer files are now named to include the image name and tuning architecture
through the SDK_NAME variable.
• Images and related files are now installed into a directory that is specific to the machine, instead of
a parent directory containing output files for multiple machines. The DEPLOY_DIR_IMAGE variable
continues to point to the directory containing images for the current MACHINE and should be used
anywhere there is a need to refer to this directory. The runqemu script now uses this variable to find
images and kernel binaries and will use BitBake to determine the directory. Alternatively, you can
set the DEPLOY_DIR_IMAGE variable in the external environment.
• When buildhistory is enabled, its output is now written under the Build Directory [http://
www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#build-directory] rather than TMPDIR.
Doing so makes it easier to delete TMPDIR and preserve the build history. Additionally, data for
produced SDKs is now split by IMAGE_NAME.
• The pkgdata directory produced as part of the packaging process has been collapsed into a single
machine-specific directory. This directory is located under sysroots and uses a machine-specific
name (i.e. tmp/sysroots/machine/pkgdata).

5.4.6. Shortened GitSRCREV Values
BitBake will now shorten revisions from Git repositories from the normal 40 characters down to 10
characters within SRCPV for improved usability in path and file names. This change should be safe
within contexts where these revisions are used because the chances of spatially close collisions is
very low. Distant collisions are not a major issue in the way the values are used.

5.4.7. IMAGE_FEATURES
The following changes have been made that relate to IMAGE_FEATURES:
• The value of IMAGE_FEATURES is now validated to ensure invalid feature items are not added.
Some users mistakenly add package names to this variable instead of using IMAGE_INSTALL in

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Migrating to a Newer Yocto Project Release

order to have the package added to the image, which does not work. This change is intended to
catch those kinds of situations. Valid IMAGE_FEATURES are drawn from PACKAGE_GROUP definitions,
COMPLEMENTARY_GLOB and a new "validitems" varflag on IMAGE_FEATURES. The "validitems" varflag
change allows additional features to be added if they are not provided using the previous two
mechanisms.
• The previously deprecated "apps-console-core" IMAGE_FEATURES item is no longer supported. Add
"splash" to IMAGE_FEATURES if you wish to have the splash screen enabled, since this is all that
apps-console-core was doing.

5.4.8. /run
The /run directory from the Filesystem Hierarchy Standard 3.0 has been introduced. You can find
some of the implications for this change here [http://cgit.openembedded.org/openembedded-core/
commit/?id=0e326280a15b0f2c4ef2ef4ec441f63f55b75873]. The change also means that recipes
that install files to /var/run must be changed. You can find a guide on how to make these changes
here [http://permalink.gmane.org/gmane.comp.handhelds.openembedded/58530].

5.4.9. Removal of Package Manager Database Within
Image Recipes
The image core-image-minimal no longer adds remove_packaging_data_files to
ROOTFS_POSTPROCESS_COMMAND. This addition is now handled automatically when "packagemanagement" is not in IMAGE_FEATURES. If you have custom image recipes that make this addition,
you should remove the lines, as they are not needed and might interfere with correct operation of
postinstall scripts.

5.4.10. Images Now Rebuild Only on Changes Instead of
Every Time
The do_rootfs and other related image construction tasks are no longer marked as "nostamp".
Consequently, they will only be re-executed when their inputs have changed. Previous versions of
the OpenEmbedded build system always rebuilt the image when requested rather when necessary.

5.4.11. Task Recipes
The previously deprecated task.bbclass has now been dropped. For recipes that previously inherited
from this class, you should rename them from task-* to packagegroup-* and inherit packagegroup
instead.
For more information, see the "packagegroup.bbclass" section.

5.4.12. BusyBox
By default, we now split BusyBox into two binaries: one that is suid root for those components that
need it, and another for the rest of the components. Splitting BusyBox allows for optimization that
eliminates the tinylogin recipe as recommended by upstream. You can disable this split by setting
BUSYBOX_SPLIT_SUID to "0".

5.4.13. Automated Image Testing
A new automated image testing framework has been added through the testimage*.bbclass class.
This framework replaces the older imagetest-qemu framework.
You can learn more about performing automated image tests in the "Performing Automated
Runtime Testing [http://www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#performingautomated-runtime-testing]" section.

5.4.14. Build History
Following are changes to Build History:

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• Installed package sizes: installed-package-sizes.txt for an image now records the size of the
files installed by each package instead of the size of each compressed package archive file.
• The dependency graphs (depends*.dot) now use the actual package names instead of replacing
dashes, dots and plus signs with underscores.
• The buildhistory-diff and buildhistory-collect-srcrevs utilities have improved commandline handling. Use the ##help option for each utility for more information on the new syntax.
For more information on Build History, see the "Maintaining Build Output Quality" section.

5.4.15. udev
Following are changes to udev:
• udev no longer brings in udev-extraconf automatically through RRECOMMENDS, since this was
originally intended to be optional. If you need the extra rules, then add udev-extraconf to your
image.
• udev no longer brings in pciutils-ids or usbutils-ids through RRECOMMENDS. These are not
needed by udev itself and removing them saves around 350KB.

5.4.16. Removed and Renamed Recipes
• The linux-yocto 3.2 kernel has been removed.
• libtool-nativesdk has been renamed to nativesdk-libtool.
• tinylogin has been removed. It has been replaced by a suid portion of Busybox. See the "BusyBox"
section for more information.
• external-python-tarball has been renamed to buildtools-tarball.
• web-webkit has been removed. It has been functionally replaced by midori.
• imake has been removed. It is no longer needed by any other recipe.
• transfig-native has been removed. It is no longer needed by any other recipe.
• anjuta-remote-run has been removed. Anjuta IDE integration has not been officially supported
for several releases.

5.4.17. Other Changes
Following is a list of short entries describing other changes:
• run-postinsts: Make this generic.
• base-files: Remove the unnecessary media/xxx directories.
• alsa-state: Provide an empty asound.conf by default.
• classes/image: Ensure BAD_RECOMMENDATIONS supports pre-renamed package names.
• classes/rootfs_rpm: Implement BAD_RECOMMENDATIONS for RPM.
• systemd: Remove systemd_unitdir if systemd is not in DISTRO_FEATURES.
• systemd: Remove init.d dir if systemd unit file is present and sysvinit is not a distro feature.
• libpam: Deny all services for the OTHER entries.
• image.bbclass: Move runtime_mapping_rename to avoid conflict with multilib. See YOCTO #4993
[https://bugzilla.yoctoproject.org/show_bug.cgi?id=4993] in Bugzilla for more information.
• linux-dtb: Use kernel build system to generate the dtb files.
• kern-tools: Switch from guilt to new kgit-s2q tool.

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5.5. Moving to the Yocto Project 1.6 Release
This section provides migration information for moving to the Yocto Project 1.6 Release from the prior
release.

5.5.1. archiver Class
The archiver class has been rewritten and its configuration has been simplified.
For more details on the source archiver, see the "Maintaining Open Source License
Compliance During Your Product's Lifecycle [http://www.yoctoproject.org/docs/1.8/dev-manual/devmanual.html#maintaining-open-source-license-compliance-during-your-products-lifecycle]" section
in the Yocto Project Development Manual.

5.5.2. Packaging Changes
The following packaging changes have been made:
• The binutils recipe no longer produces a binutils-symlinks package. update-alternatives is
now used to handle the preferred binutils variant on the target instead.
• The tc (traffic control) utilities have been split out of the main iproute2 package and put into the
iproute2-tc package.
• The gtk-engines schemas have been moved to a dedicated gtk-engines-schemas package.
• The armv7a with thumb package architecture suffix has changed. The suffix for these packages
with the thumb optimization enabled is "t2" as it should be. Use of this suffix was not the case in
the 1.5 release. Architecture names will change within package feeds as a result.

5.5.3. BitBake
The following changes have been made to BitBake [http://www.yoctoproject.org/docs/1.8/devmanual/dev-manual.html#bitbake-term].

5.5.3.1. Matching Branch Requirement for Git Fetching
When fetching source from a Git repository using SRC_URI, BitBake will now validate the SRCREV value
against the branch. You can specify the branch using the following form:
SRC_URI = "git://server.name/repository;branch=branchname"
If you do not specify a branch, BitBake looks in the default "master" branch.
Alternatively, if you need to bypass this check (e.g. if you are fetching a revision corresponding to a
tag that is not on any branch), you can add ";nobranch=1" to the end of the URL within SRC_URI.

5.5.3.2. Python Definition substitutions
BitBake had some previously deprecated Python definitions within its bb module removed. You should
use their sub-module counterparts instead:
• bb.MalformedUrl: Use bb.fetch.MalformedUrl.
• bb.fetch.encodeurl: Use bb.fetch.encodeurl.
• bb.decodeurl: Use bb.fetch.decodeurl
• bb.mkdirhier: Use bb.utils.mkdirhier.
• bb.movefile: Use bb.utils.movefile.
• bb.copyfile: Use bb.utils.copyfile.
• bb.which: Use bb.utils.which.

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• bb.vercmp_string: Use bb.utils.vercmp_string.
• bb.vercmp: Use bb.utils.vercmp.

5.5.3.3. SVK Fetcher
The SVK fetcher has been removed from BitBake.

5.5.3.4. Console Output Error Redirection
The BitBake console UI will now output errors to stderr instead of stdout. Consequently, if you are
piping or redirecting the output of bitbake to somewhere else, and you wish to retain the errors, you
will need to add 2>&1 (or something similar) to the end of your bitbake command line.

5.5.3.5. task-taskname Overrides
task-taskname overrides have been adjusted so that tasks whose names contain underscores have
the underscores replaced by hyphens for the override so that they now function properly. For example,
the task override for do_populate_sdk is task-populate-sdk.

5.5.4. Changes to Variables
The following variables have changed. For information on the OpenEmbedded build system variables,
see the "Variables Glossary" Chapter.

5.5.4.1. TMPDIR
TMPDIR can no longer be on an NFS mount. NFS does not offer full POSIX locking and inode consistency
and can cause unexpected issues if used to store TMPDIR.
The check for this occurs on startup. If TMPDIR is detected on an NFS mount, an error occurs.

5.5.4.2. PRINC
The PRINC variable has been deprecated and triggers a warning if detected during a build.
For PR increments on changes, use the PR service instead. You can find out more about this
service in the "Working With a PR Service [http://www.yoctoproject.org/docs/1.8/dev-manual/devmanual.html#working-with-a-pr-service]" section in the Yocto Project Development Manual.

5.5.4.3. IMAGE_TYPES
The "sum.jffs2" option for IMAGE_TYPES has been replaced by the "jffs2.sum" option, which fits the
processing order.

5.5.4.4. COPY_LIC_MANIFEST
The COPY_LIC_MANIFEST variable must now be set to "1" rather than any value in order to enable it.

5.5.4.5. COPY_LIC_DIRS
The COPY_LIC_DIRS variable must now be set to "1" rather than any value in order to enable it.

5.5.4.6. PACKAGE_GROUP
The PACKAGE_GROUP variable has been renamed to FEATURE_PACKAGES to more accurately reflect its
purpose. You can still use PACKAGE_GROUP but the OpenEmbedded build system produces a warning
message when it encounters the variable.

5.5.5. Directory Layout Changes
The meta-hob layer has been removed from the top-level of the Source Directory [http://
www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#source-directory]. The contents of this
layer are no longer needed by the Hob user interface for building images and toolchains.

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5.5.6. Package Test (ptest)
Package Tests (ptest) are built but not installed by default. For information on using Package Tests, see
the "Setting up and running package test (ptest) [http://www.yoctoproject.org/docs/1.8/dev-manual/
dev-manual.html#testing-packages-with-ptest]" section in the Yocto Project Development Manual.
For information on the ptest class, see the "ptest.bbclass" section.

5.5.7. Build Changes
Separate build and source directories have been enabled by default for selected recipes where it
is known to work (a whitelist) and for all recipes that inherit the cmake class. In future releases the
autotools class will enable a separate build directory by default as well. Recipes building Autotoolsbased software that fails to build with a separate build directory should be changed to inherit from
the autotools-brokensep class instead of the autotools class.

5.5.8. qemu-native
qemu-native now builds without SDL-based graphical output support by default. The following
additional lines are needed in your local.conf to enable it:
PACKAGECONFIG_pn-qemu-native = "sdl"
ASSUME_PROVIDED += "libsdl-native"

Note
The default local.conf contains these statements. Consequently, if you are building a
headless system and using a default local.conf file, you will need comment these two lines
out.

5.5.9. core-image-basic
core-image-basic has been renamed to core-image-full-cmdline.
In addition to core-image-basic being renamed, packagegroup-core-basic has been renamed to
packagegroup-core-full-cmdline to match.

5.5.10. Licensing
The top-level LICENSE file has been changed to better describe the license of the various components
of OE-Core. However, the licensing itself remains unchanged.
Normally, this change would not cause any side-effects. However, some recipes point to this file
within LIC_FILES_CHKSUM (as ${COREBASE}/LICENSE) and thus the accompanying checksum must be
changed from 3f40d7994397109285ec7b81fdeb3b58 to 4d92cd373abda3937c2bc47fbc49d690. A
better alternative is to have LIC_FILES_CHKSUM point to a file describing the license that is distributed
with the source that the recipe is building, if possible, rather than pointing to ${COREBASE}/LICENSE.

5.5.11. CFLAGS Options
The "-fpermissive" option has been removed from the default CFLAGS value. You need to take action
on individual recipes that fail when building with this option. You need to either patch the recipes to
fix the issues reported by the compiler, or you need to add "-fpermissive" to CFLAGS in the recipes.

5.5.12. Custom Image Output Types
Custom image output types, as selected using IMAGE_FSTYPES, must declare their dependencies on
other image types (if any) using a new IMAGE_TYPEDEP variable.

5.5.13. Tasks
The do_package_write task has been removed. The task is no longer needed.

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5.5.14. update-alternative Provider
The default update-alternatives provider has been changed from opkg to opkg-utils. This change
resolves some troublesome circular dependencies. The runtime package has also been renamed from
update-alternatives-cworth to update-alternatives-opkg.

5.5.15. virtclass Overrides
The virtclass overrides are now deprecated. Use the equivalent class overrides instead (e.g.
virtclass-native becomes class-native.)

5.5.16. Removed and Renamed Recipes
The following recipes have been removed:
• packagegroup-toolset-native - This recipe is largely unused.
• linux-yocto-3.8 - Support for the Linux yocto 3.8 kernel has been dropped. Support for the 3.10
and 3.14 kernels have been added with the linux-yocto-3.10 and linux-yocto-3.14 recipes.
• ocf-linux - This recipe has been functionally replaced using cryptodev-linux.
• genext2fs - genext2fs is no longer used by the build system and is unmaintained upstream.
• js - This provided an ancient version of Mozilla's javascript engine that is no longer needed.
• zaurusd - The recipe has been moved to the meta-handheld layer.
• eglibc 2.17 - Replaced by the eglibc 2.19 recipe.
• gcc 4.7.2 - Replaced by the now stable gcc 4.8.2.
• external-sourcery-toolchain - this recipe is now maintained in the meta-sourcery layer.
• linux-libc-headers-yocto 3.4+git - Now using version 3.10 of the linux-libc-headers by
default.
• meta-toolchain-gmae - This recipe is obsolete.
• packagegroup-core-sdk-gmae - This recipe is obsolete.
• packagegroup-core-standalone-gmae-sdk-target - This recipe is obsolete.

5.5.17. Removed Classes
The following classes have become obsolete and have been removed:
• module_strip
• pkg_metainfo
• pkg_distribute
• image-empty

5.5.18. Reference Board Support Packages (BSPs)
The following reference BSPs changes occurred:
• The BeagleBoard (beagleboard) ARM reference hardware has been replaced by the BeagleBone
(beaglebone) hardware.
• The RouterStation Pro (routerstationpro) MIPS reference hardware has been replaced by the
EdgeRouter Lite (edgerouter) hardware.
The previous reference BSPs for the beagleboard and routerstationpro machines are still available
in a new meta-yocto-bsp-old layer in the Source Repositories [http://git.yoctoproject.org] at http://
git.yoctoproject.org/cgit/cgit.cgi/meta-yocto-bsp-old/.

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5.6. Moving to the Yocto Project 1.7 Release
This section provides migration information for moving to the Yocto Project 1.7 Release from the prior
release.

5.6.1. Changes to Setting QEMUPACKAGECONFIG Options
in local.conf
The QEMU recipe now uses a number of PACKAGECONFIG options to enable various optional features.
The method used to set defaults for these options means that existing local.conf files will need to be
be modified to append to PACKAGECONFIG for qemu-native and nativesdk-qemu instead of setting it.
In other words, to enable graphical output for QEMU, you should now have these lines in local.conf:
PACKAGECONFIG_append_pn-qemu-native = " sdl"
PACKAGECONFIG_append_pn-nativesdk-qemu = " sdl"

5.6.2. Minimum Git version
The minimum Git [http://www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#git] version
required on the build host is now 1.7.8 because the ##list option is now required by BitBake's
Git fetcher. As always, if your host distribution does not provide a version of Git that meets this
requirement, you can use the buildtools-tarball that does. See the "Required Git, tar, and Python
Versions" section for more information.

5.6.3. Autotools Class Changes
The following autotools class changes occurred:
• A separate build directory is now used by default: The autotools class has been changed to use a
directory for building (B), which is separate from the source directory (S). This is commonly referred
to as B != S, or an out-of-tree build.
If the software being built is already capable of building in a directory separate from the source, you
do not need to do anything. However, if the software is not capable of being built in this manner,
you will need to either patch the software so that it can build separately, or you will need to change
the recipe to inherit the autotools-brokensep class instead of the autotools class.
• The ##foreign option is no longer passed to automake when running autoconf: This option tells
automake that a particular software package does not follow the GNU standards and therefore
should not be expected to distribute certain files such as ChangeLog, AUTHORS, and so forth.
Because the majority of upstream software packages already tell automake to enable foreign mode
themselves, the option is mostly superfluous. However, some recipes will need patches for this
change. You can easily make the change by patching configure.ac so that it passes "foreign"
to AM_INIT_AUTOMAKE(). See this commit [http://cgit.openembedded.org/openembedded-core/
commit/?id=01943188f85ce6411717fb5bf702d609f55813f2] for an example showing how to make
the patch.

5.6.4. Binary Configuration Scripts Disabled
Some of the core recipes that package binary configuration scripts now disable the scripts due to the
scripts previously requiring error-prone path substitution. Software that links against these libraries
using these scripts should use the much more robust pkg-config instead. The list of recipes changed
in this version (and their configuration scripts) is as follows:
directfb (directfb-config)
freetype (freetype-config)
gpgme (gpgme-config)
libassuan (libassuan-config)
libcroco (croco-6.0-config)
libgcrypt (libgcrypt-config)

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libgpg-error (gpg-error-config)
libksba (ksba-config)
libpcap (pcap-config)
libpcre (pcre-config)
libpng (libpng-config, libpng16-config)
libsdl (sdl-config)
libusb-compat (libusb-config)
libxml2 (xml2-config)
libxslt (xslt-config)
ncurses (ncurses-config)
neon (neon-config)
npth (npth-config)
pth (pth-config)
taglib (taglib-config)
Additionally, support for pkg-config has been added to some recipes in the previous list in the rare
cases where the upstream software package does not already provide it.

5.6.5. eglibc 2.19 Replaced with glibc 2.20
Because eglibc and glibc were already fairly close, this replacement should not require any
significant changes to other software that links to eglibc. However, there were a number of minor
changes in glibc 2.20 upstream that could require patching some software (e.g. the removal of the
_BSD_SOURCE feature test macro).
glibc 2.20 requires version 2.6.32 or greater of the Linux kernel. Thus, older kernels will no longer
be usable in conjunction with it.
For full details on the changes in glibc 2.20, see the upstream release notes here [https://
sourceware.org/ml/libc-alpha/2014-09/msg00088.html].

5.6.6. Kernel Module Autoloading
The module_autoload_* variable is now deprecated and a new KERNEL_MODULE_AUTOLOAD variable
should be used instead. Also, module_conf_* must now be used in conjunction with a new
KERNEL_MODULE_PROBECONF variable. The new variables no longer require you to specify the module
name as part of the variable name. This change not only simplifies usage but also allows the values of
these variables to be appropriately incorporated into task signatures and thus trigger the appropriate
tasks to re-execute when changed. You should replace any references to module_autoload_*
with KERNEL_MODULE_AUTOLOAD, and add any modules for which module_conf_* is specified to
KERNEL_MODULE_PROBECONF.
For more information, see the KERNEL_MODULE_AUTOLOAD and KERNEL_MODULE_PROBECONF variables.

5.6.7. QA Check Changes
The following changes have occurred to the QA check process:
• Additional QA checks file-rdeps and build-deps have been added in order to verify that file
dependencies are satisfied (e.g. package contains a script requiring /bin/bash) and build-time
dependencies are declared, respectively. For more information, please see the "QA Error and
Warning Messages" chapter.
• Package QA checks are now performed during a new do_package_qa task rather than being part
of the do_package task. This allows more parallel execution. This change is unlikely to be an issue
except for highly customized recipes that disable packaging tasks themselves by marking them as
noexec. For those packages, you will need to disable the do_package_qa task as well.
• Files being overwritten during the do_populate_sysroot task now trigger an error instead of a
warning. Recipes should not be overwriting files written to the sysroot by other recipes. If you have
these types of recipes, you need to alter them so that they do not overwrite these files.
You might now receive this error after changes in configuration or metadata resulting in orphaned
files being left in the sysroot. If you do receive this error, the way to resolve the issue is to delete

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your TMPDIR or to move it out of the way and then re-start the build. Anything that has been fully
built up to that point and does not need rebuilding will be restored from the shared state cache and
the rest of the build will be able to proceed as normal.

5.6.8. Removed Recipes
The following recipes have been removed:
• x-load: This recipe has been superseded by U-boot SPL for all Cortex-based TI SoCs. For legacy
boards, the meta-ti layer, which contains a maintained recipe, should be used instead.
• ubootchart: This recipe is obsolete. A bootchart2 recipe has been added to functionally replace it.
• linux-yocto 3.4: Support for the linux-yocto 3.4 kernel has been dropped. Support for the 3.10
and 3.14 kernels remains, while support for version 3.17 has been added.
• eglibc has been removed in favor of glibc. See the "eglibc 2.19 Replaced with glibc 2.20"
section for more information.

5.6.9. Miscellaneous Changes
The following miscellaneous change occurred:
• The build history feature now writes build-id.txt instead of build-id. Additionally, buildid.txt now contains the full build header as printed by BitBake upon starting the build. You should
manually remove old "build-id" files from your existing build history repositories to avoid confusion.
For information on the build history feature, see the "Maintaining Build Output Quality" section.

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Chapter 6. Source Directory
Structure
The Source Directory [http://www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#sourcedirectory] consists of several components. Understanding them and knowing where they are located
is key to using the Yocto Project well. This chapter describes the Source Directory and gives
information about the various files and directories.
For information on how to establish a local Source Directory on your development system, see
the "Getting Set Up [http://www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#gettingsetup]" section in the Yocto Project Development Manual.

Note
The OpenEmbedded build system does not support file or directory names that contain
spaces. Be sure that the Source Directory you use does not contain these types of names.

6.1. Top-Level Core Components
This section describes the top-level components of the Source Directory [http://www.yoctoproject.org/
docs/1.8/dev-manual/dev-manual.html#source-directory].

6.1.1. bitbake/
This directory includes a copy of BitBake for ease of use. The copy usually matches the current
stable BitBake release from the BitBake project. BitBake, a Metadata [http://www.yoctoproject.org/
docs/1.8/dev-manual/dev-manual.html#metadata] interpreter, reads the Yocto Project Metadata and
runs the tasks defined by that data. Failures are usually from the Metadata and not from BitBake
itself. Consequently, most users do not need to worry about BitBake.
When you run the bitbake command, the main BitBake executable, which resides in the bitbake/
bin/ directory, starts. Sourcing an environment setup script (e.g. oe-init-build-env or oe-initbuild-env-memres) places the scripts and bitbake/bin directories (in that order) into the shell's
PATH environment variable.
For more information on BitBake, see the BitBake User Manual [http://www.yoctoproject.org/docs/1.8/
bitbake-user-manual/bitbake-user-manual.html].

6.1.2. build/
This directory contains user configuration files and the output generated by the OpenEmbedded
build system in its standard configuration where the source tree is combined with the output. The
Build Directory [http://www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#build-directory]
is created initially when you source the OpenEmbedded build environment setup script (i.e. oe-initbuild-env or oe-init-build-env-memres).
It is also possible to place output and configuration files in a directory separate from the Source
Directory [http://www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#source-directory] by
providing a directory name when you source the setup script. For information on separating output
from your local Source Directory files, see the "oe-init-build-env and "oe-init-build-envmemres" sections.

6.1.3. documentation/
This directory holds the source for the Yocto Project documentation as well as templates and tools
that allow you to generate PDF and HTML versions of the manuals. Each manual is contained in a
sub-folder. For example, the files for this manual reside in the ref-manual/ directory.

6.1.4. meta/
This directory contains the OpenEmbedded Core metadata. The directory holds recipes, common
classes, and machine configuration for emulated targets (qemux86, qemuarm, and so forth.)

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Source Directory Structure

6.1.5. meta-yocto/
This directory contains the configuration for the Poky reference distribution.

6.1.6. meta-yocto-bsp/
This directory contains the Yocto Project reference hardware Board Support Packages (BSPs). For more
information on BSPs, see the Yocto Project Board Support Package (BSP) Developer's Guide [http://
www.yoctoproject.org/docs/1.8/bsp-guide/bsp-guide.html].

6.1.7. meta-selftest/
This directory adds additional recipes and append files used by the OpenEmbedded selftests to verify
the behavior of the build system.
You do not have to add this layer to your bblayers.conf file unless you want to run the selftests.

6.1.8. meta-skeleton/
This directory contains template recipes for BSP and kernel development.

6.1.9. scripts/
This directory contains various integration scripts that implement extra functionality in the Yocto
Project environment (e.g. QEMU scripts). The oe-init-build-env and oe-init-build-env-memres
scripts append this directory to the shell's PATH environment variable.
The scripts directory has useful scripts that assist in contributing back to the Yocto Project, such as
create-pull-request and send-pull-request.

6.1.10. oe-init-build-env
This script is one of two scripts that set up the OpenEmbedded build environment. For information
on the other script, see the "oe-init-build-env-memres" section.
Running this script with the source command in a shell makes changes to PATH and sets other core
BitBake variables based on the current working directory. You need to run an environment setup script
before running BitBake commands. The script uses other scripts within the scripts directory to do
the bulk of the work.
When you run this script, your Yocto Project environment is set up, a Build Directory [http://
www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#build-directory] is created, your
working directory becomes the Build Directory, and you are presented with a list of common BitBake
targets. Here is an example:
$ source oe-init-build-env
### Shell environment set up for builds. ###
You can now run 'bitbake '
Common targets are:
core-image-minimal
core-image-sato
meta-toolchain
adt-installer
meta-ide-support
You can also run generated qemu images with a command like 'runqemu qemux86'
The script gets its default list of common targets from the conf-notes.txt file, which is found
in the meta-yocto directory within the Source Directory [http://www.yoctoproject.org/docs/1.8/

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dev-manual/dev-manual.html#source-directory]. Should you have custom distributions, it is very
easy to modify this configuration file to include your targets for your distribution. See the
"Creating a Custom Template Configuration Directory [http://www.yoctoproject.org/docs/1.8/devmanual/dev-manual.html#creating-a-custom-template-configuration-directory]" section in the Yocto
Project Development Manual for more information.
By default, running this script without a Build Directory [http://www.yoctoproject.org/docs/1.8/devmanual/dev-manual.html#build-directory] argument creates the build directory in your current
working directory. If you provide a Build Directory argument when you source the script, you direct
the OpenEmbedded build system to create a Build Directory of your choice. For example, the following
command creates a Build Directory named mybuilds that is outside of the Source Directory [http://
www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#source-directory]:
$ source oe-init-build-env ~/mybuilds
The OpenEmbedded build system uses the template configuration files, which are found by default
in the meta-yocto/conf directory in the Source Directory [http://www.yoctoproject.org/docs/1.8/
dev-manual/dev-manual.html#source-directory]. See the "Creating a Custom Template Configuration
Directory [http://www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#creating-a-customtemplate-configuration-directory]" section in the Yocto Project Development Manual for more
information.

Note
The OpenEmbedded build system does not support file or directory names that contain
spaces. If you attempt to run the oe-init-build-env script from a Source Directory that
contains spaces in either the filenames or directory names, the script returns an error
indicating no such file or directory. Be sure to use a Source Directory free of names containing
spaces.

6.1.11. oe-init-build-env-memres
This script is one of two scripts that set up the OpenEmbedded build environment. Aside from setting
up the environment, this script starts a memory-resident BitBake server. For information on the other
setup script, see the "oe-init-build-env" section.
Memory-resident BitBake resides in memory until you specifically remove it using the following
BitBake command:
$ bitbake -m
Running this script with the source command in a shell makes changes to PATH and sets other core
BitBake variables based on the current working directory. One of these variables is the BBSERVER
variable, which allows the OpenEmbedded build system to locate the server that is running BitBake.
You need to run an environment setup script before using BitBake commands. Following is the script
syntax:
$ source oe-init-build-env-memres port_number build_dir
The script uses other scripts within the scripts directory to do the bulk of the work.
If you do not provide a port number with the script, the BitBake server at port "12345" is started.
When you run this script, your Yocto Project environment is set up, a Build Directory [http://
www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#build-directory] is created, your
working directory becomes the Build Directory, and you are presented with a list of common BitBake
targets. Here is an example:

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Source Directory Structure

$ source oe-init-build-env-memres
No port specified, using dynamically selected port
### Shell environment set up for builds. ###
You can now run 'bitbake '
Common targets are:
core-image-minimal
core-image-sato
meta-toolchain
adt-installer
meta-ide-support
You can also run generated qemu images with a command like 'runqemu qemux86'
Bitbake server started on demand as needed, use bitbake -m to shut it down
The script gets its default list of common targets from the conf-notes.txt file, which is found
in the meta-yocto directory within the Source Directory [http://www.yoctoproject.org/docs/1.8/
dev-manual/dev-manual.html#source-directory]. Should you have custom distributions, it is very
easy to modify this configuration file to include your targets for your distribution. See the
"Creating a Custom Template Configuration Directory [http://www.yoctoproject.org/docs/1.8/devmanual/dev-manual.html#creating-a-custom-template-configuration-directory]" section in the Yocto
Project Development Manual for more information.
By default, running this script without a Build Directory [http://www.yoctoproject.org/docs/1.8/devmanual/dev-manual.html#build-directory] argument creates a build directory named build. If you
provide a Build Directory argument when you source the script, the Build Directory is created using
that name. For example, the following command starts the BitBake server using the default port
"12345" and creates a Build Directory named mybuilds that is outside of the Source Directory [http://
www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#source-directory]:
$ source oe-init-build-env-memres ~/mybuilds
The OpenEmbedded build system uses the template configuration files, which are found by default
in the meta-yocto/conf directory in the Source Directory [http://www.yoctoproject.org/docs/1.8/
dev-manual/dev-manual.html#source-directory]. See the "Creating a Custom Template Configuration
Directory [http://www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#creating-a-customtemplate-configuration-directory]" section in the Yocto Project Development Manual for more
information.

Note
The OpenEmbedded build system does not support file or directory names that contain
spaces. If you attempt to run the oe-init-build-env-memres script from a Source Directory
that contains spaces in either the filenames or directory names, the script returns an error
indicating no such file or directory. Be sure to use a Source Directory free of names containing
spaces.

6.1.12. LICENSE, README, and README.hardware
These files are standard top-level files.

6.2. The Build Directory -build/
The OpenEmbedded build system creates the Build Directory [http://www.yoctoproject.org/docs/1.8/
dev-manual/dev-manual.html#build-directory] when you run one of the build environment setup
scripts (i.e. oe-init-build-env or oe-init-build-env-memres).
If you do not give the Build Directory a specific name when you run a setup script, the name defaults
to build.

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The TOPDIR variable points to the Build Directory.

6.2.1. build/buildhistory
The OpenEmbedded build system creates this directory when you enable the build history feature.
The directory tracks build information into image, packages, and SDK subdirectories. For information
on the build history feature, see the "Maintaining Build Output Quality" section.

6.2.2. build/conf/local.conf
This configuration file contains all the local user configurations for your build environment. The
local.conf file contains documentation on the various configuration options. Any variable set here
overrides any variable set elsewhere within the environment unless that variable is hard-coded within
a file (e.g. by using '=' instead of '?='). Some variables are hard-coded for various reasons but these
variables are relatively rare.
Edit this file to set the MACHINE for which you want to build, which package types you wish to use
(PACKAGE_CLASSES), the location from which you want to access downloaded files (DL_DIR), and how
you want your host machine to use resources (BB_NUMBER_THREADS and PARALLEL_MAKE).
If local.conf is not present when you start the build, the OpenEmbedded build system creates it
from local.conf.sample when you source the top-level build environment setup script (i.e. oeinit-build-env or oe-init-build-env-memres).
The source local.conf.sample file used depends on the $TEMPLATECONF script variable, which
defaults to meta-yocto/conf when you are building from the Yocto Project development environment
and defaults to meta/conf when you are building from the OpenEmbedded Core environment.
Because the script variable points to the source of the local.conf.sample file, this implies that you
can configure your build environment from any layer by setting the variable in the top-level build
environment setup script as follows:
TEMPLATECONF=your_layer/conf
Once the build process gets the sample file, it uses sed to substitute final ${OEROOT} values for all
##OEROOT## values.

Note
You can see how the TEMPLATECONF variable is used by looking at the scripts/oesetup-builddir script in the Source Directory [http://www.yoctoproject.org/docs/1.8/devmanual/dev-manual.html#source-directory]. You can find the Yocto Project version of the
local.conf.sample file in the meta-yocto/conf directory.

6.2.3. build/conf/bblayers.conf
This configuration file defines layers [http://www.yoctoproject.org/docs/1.8/dev-manual/devmanual.html#understanding-and-creating-layers], which are directory trees, traversed (or walked)
by BitBake. The bblayers.conf file uses the BBLAYERS variable to list the layers BitBake tries to find,
and uses the BBLAYERS_NON_REMOVABLE variable to list layers that must not be removed.
If bblayers.conf is not present when you start the build, the OpenEmbedded build system creates
it from bblayers.conf.sample when you source the top-level build environment setup script (i.e.
oe-init-build-env or oe-init-build-env-memres).
The source bblayers.conf.sample file used depends on the $TEMPLATECONF script variable, which
defaults to meta-yocto/conf when you are building from the Yocto Project development environment
and defaults to meta/conf when you are building from the OpenEmbedded Core environment.
Because the script variable points to the source of the bblayers.conf.sample file, this implies that
you can base your build from any layer by setting the variable in the top-level build environment
setup script as follows:
TEMPLATECONF=your_layer/conf

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Source Directory Structure

Once the build process gets the sample file, it uses sed to substitute final ${OEROOT} values for all
##OEROOT## values.

Note
You
can
see
how
the
TEMPLATECONF
variable
scripts/oe-setup-builddir
script in the Source Directory [http://www.yoctoproject.org/docs/1.8/dev-manual/devmanual.html#source-directory]. You can find the Yocto Project version of the
bblayers.conf.sample file in the meta-yocto/conf directory.

6.2.4. build/conf/sanity_info
This file indicates the state of the sanity checks and is created during the build.

6.2.5. build/downloads/
This directory contains downloaded upstream source tarballs. You can reuse the directory for multiple
builds or move the directory to another location. You can control the location of this directory through
the DL_DIR variable.

6.2.6. build/sstate-cache/
This directory contains the shared state cache. You can reuse the directory for multiple builds or
move the directory to another location. You can control the location of this directory through the
SSTATE_DIR variable.

6.2.7. build/tmp/
The OpenEmbedded build system creates and uses this directory for all the build system's output.
The TMPDIR variable points to this directory.
BitBake creates this directory if it does not exist. As a last resort, to clean up a build and start it
from scratch (other than the downloads), you can remove everything in the tmp directory or get rid
of the directory completely. If you do, you should also completely remove the build/sstate-cache
directory.

6.2.8. build/tmp/buildstats/
This directory stores the build statistics.

6.2.9. build/tmp/cache/
When BitBake parses the metadata, it creates a cache file of the result that can be used when
subsequently running commands. BitBake stores these results here on a per-machine basis.

6.2.10. build/tmp/deploy/
This directory contains any "end result" output from the OpenEmbedded build process. The
DEPLOY_DIR variable points to this directory. For more detail on the contents of the deploy directory,
see the "Images" and "Application Development SDK" sections.

6.2.11. build/tmp/deploy/deb/
This directory receives any .deb packages produced by the build process. The packages are sorted
into feeds for different architecture types.

6.2.12. build/tmp/deploy/rpm/
This directory receives any .rpm packages produced by the build process. The packages are sorted
into feeds for different architecture types.

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Source Directory Structure

6.2.13. build/tmp/deploy/ipk/
This directory receives .ipk packages produced by the build process.

6.2.14. build/tmp/deploy/licenses/
This directory receives package licensing information. For example, the directory contains
sub-directories for bash, busybox, and eglibc (among others) that in turn contain
appropriate COPYING license files with other licensing information. For information on
licensing, see the "Maintaining Open Source License Compliance During Your Product's
Lifecycle
[http://www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#maintaining-opensource-license-compliance-during-your-products-lifecycle]" section.

6.2.15. build/tmp/deploy/images/
This directory receives complete filesystem images. If you want to flash the resulting image from a
build onto a device, look here for the image.
Be careful when deleting files in this directory. You can safely delete old images from this directory
(e.g. core-image-*, hob-image-*, etc.). However, the kernel (*zImage*, *uImage*, etc.), bootloader
and other supplementary files might be deployed here prior to building an image. Because these
files are not directly produced from the image, if you delete them they will not be automatically recreated when you build the image again.
If you do accidentally delete files here, you will need to force them to be re-created. In order to do
that, you will need to know the target that produced them. For example, these commands rebuild
and re-create the kernel files:
$ bitbake -c clean virtual/kernel
$ bitbake virtual/kernel

6.2.16. build/tmp/deploy/sdk/
The OpenEmbedded build system creates this directory to hold toolchain installer scripts, which
when executed, install the sysroot that matches your target hardware. You can find out more about
these installers in the "Optionally Building a Toolchain Installer [http://www.yoctoproject.org/docs/1.8/
adt-manual/adt-manual.html#optionally-building-a-toolchain-installer]" section in the Yocto Project
Application Developer's Guide.

6.2.17. build/tmp/sstate-control/
The OpenEmbedded build system uses this directory for the shared state manifest files. The shared
state code uses these files to record the files installed by each sstate task so that the files can be
removed when cleaning the recipe or when a newer version is about to be installed. The build system
also uses the manifests to detect and produce a warning when files from one task are overwriting
those from another.

6.2.18. build/tmp/sysroots/
This directory contains shared header files and libraries as well as other shared data. Packages that
need to share output with other packages do so within this directory. The directory is subdivided by
architecture so multiple builds can run within the one Build Directory.

6.2.19. build/tmp/stamps/
This directory holds information that BitBake uses for accounting purposes to track what tasks have
run and when they have run. The directory is sub-divided by architecture, package name, and version.
Following is an example:

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Source Directory Structure

stamps/all-poky-linux/distcc-config/1.0-r0.do_build-2fdd....2do
Although the files in the directory are empty of data, BitBake uses the filenames and timestamps
for tracking purposes.

6.2.20. build/tmp/log/
This directory contains general logs that are not otherwise placed using the package's WORKDIR.
Examples of logs are the output from the do_check_pkg or do_distro_check tasks. Running a build
does not necessarily mean this directory is created.

6.2.21. build/tmp/work/
This directory contains architecture-specific work sub-directories for packages built by BitBake. All
tasks execute from the appropriate work directory. For example, the source for a particular package
is unpacked, patched, configured and compiled all within its own work directory. Within the work
directory, organization is based on the package group and version for which the source is being
compiled as defined by the WORKDIR.
It is worth considering the structure of a typical work directory. As an example, consider linux-yoctokernel-3.0 on the machine qemux86 built within the Yocto Project. For this package, a work directory
of tmp/work/qemux86-poky-linux/linux-yocto/3.0+git1+<.....>, referred to as the WORKDIR, is
created. Within this directory, the source is unpacked to linux-qemux86-standard-build and then
patched by Quilt. (See the "Using a Quilt Flow [http://www.yoctoproject.org/docs/1.8/dev-manual/
dev-manual.html#using-a-quilt-workflow]" section in the Yocto Project Development Manual for
more information.) Within the linux-qemux86-standard-build directory, standard Quilt directories
linux-3.0/patches and linux-3.0/.pc are created, and standard Quilt commands can be used.
There are other directories generated within WORKDIR. The most important directory is WORKDIR/
temp/, which has log files for each task (log.do_*.pid) and contains the scripts BitBake runs for
each task (run.do_*.pid). The WORKDIR/image/ directory is where "make install" places its output
that is then split into sub-packages within WORKDIR/packages-split/.

6.2.22. build/tmp/work-shared/
For efficiency, the OpenEmbedded build system creates and uses this directory to hold recipes that
share a work directory with other recipes. In practice, this is only used for gcc and its variants (e.g.
gcc-cross, libgcc, gcc-runtime, and so forth).

6.3. The Metadata -meta/
As mentioned previously, Metadata [http://www.yoctoproject.org/docs/1.8/dev-manual/devmanual.html#metadata] is the core of the Yocto Project. Metadata has several important subdivisions:

6.3.1. meta/classes/
This directory contains the *.bbclass files. Class files are used to abstract common code so it can
be reused by multiple packages. Every package inherits the base.bbclass file. Examples of other
important classes are autotools.bbclass, which in theory allows any Autotool-enabled package to
work with the Yocto Project with minimal effort. Another example is kernel.bbclass that contains
common code and functions for working with the Linux kernel. Functions like image generation
or packaging also have their specific class files such as image.bbclass, rootfs_*.bbclass and
package*.bbclass.
For reference information on classes, see the "Classes" chapter.

6.3.2. meta/conf/
This directory contains the core set of configuration files that start from bitbake.conf and from which
all other configuration files are included. See the include statements at the end of the bitbake.conf
file and you will note that even local.conf is loaded from there. While bitbake.conf sets up the

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Source Directory Structure

defaults, you can often override these by using the (local.conf) file, machine file or the distribution
configuration file.

6.3.3. meta/conf/machine/
This directory contains all the machine configuration files. If you set MACHINE = "qemux86", the
OpenEmbedded build system looks for a qemux86.conf file in this directory. The include directory
contains various data common to multiple machines. If you want to add support for a new machine
to the Yocto Project, look in this directory.

6.3.4. meta/conf/distro/
The contents of this directory controls any distribution-specific configurations. For the Yocto Project,
the defaultsetup.conf is the main file here. This directory includes the versions and the SRCDATE
definitions for applications that are configured here. An example of an alternative configuration might
be poky-bleeding.conf. Although this file mainly inherits its configuration from Poky.

6.3.5. meta/conf/machine-sdk/
The OpenEmbedded build system searches this directory for configuration files that correspond to the
value of SDKMACHINE. By default, 32-bit and 64-bit x86 files ship with the Yocto Project that support
some SDK hosts. However, it is possible to extend that support to other SDK hosts by adding additional
configuration files in this subdirectory within another layer.

6.3.6. meta/files/
This directory contains common license files and several text files used by the build system. The text
files contain minimal device information and lists of files and directories with known permissions.

6.3.7. meta/lib/
This directory contains OpenEmbedded Python library code used during the build process.

6.3.8. meta/recipes-bsp/
This directory contains anything linking to specific hardware or hardware configuration information
such as "u-boot" and "grub".

6.3.9. meta/recipes-connectivity/
This directory contains libraries and applications related to communication with other devices.

6.3.10. meta/recipes-core/
This directory contains what is needed to build a basic working Linux image including commonly used
dependencies.

6.3.11. meta/recipes-devtools/
This directory contains tools that are primarily used by the build system. The tools, however, can
also be used on targets.

6.3.12. meta/recipes-extended/
This directory contains non-essential applications that add features compared to the alternatives
in core. You might need this directory for full tool functionality or for Linux Standard Base (LSB)
compliance.

6.3.13. meta/recipes-gnome/
This directory contains all things related to the GTK+ application framework.

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Source Directory Structure

6.3.14. meta/recipes-graphics/
This directory contains X and other graphically related system libraries

6.3.15. meta/recipes-kernel/
This directory contains the kernel and generic applications and libraries that have strong kernel
dependencies.

6.3.16. meta/recipes-lsb4/
This directory contains recipes specifically added to support the Linux Standard Base (LSB) version
4.x.

6.3.17. meta/recipes-multimedia/
This directory contains codecs and support utilities for audio, images and video.

6.3.18. meta/recipes-qt/
This directory contains all things related to the Qt application framework.

6.3.19. meta/recipes-rt/
This directory contains package and image recipes for using and testing the PREEMPT_RT kernel.

6.3.20. meta/recipes-sato/
This directory contains the Sato demo/reference UI/UX and its associated applications and
configuration data.

6.3.21. meta/recipes-support/
This directory contains recipes used by other recipes, but that are not directly included in images
(i.e. dependencies of other recipes).

6.3.22. meta/site/
This directory contains a list of cached results for various architectures. Because certain "autoconf"
test results cannot be determined when cross-compiling due to the tests not able to run on a live
system, the information in this directory is passed to "autoconf" for the various architectures.

6.3.23. meta/recipes.txt
This file is a description of the contents of recipes-*.

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Chapter 7. Classes
Class files are used to abstract common functionality and share it amongst multiple recipe (.bb) files.
To use a class file, you simply make sure the recipe inherits the class. In most cases, when a recipe
inherits a class it is enough to enable its features. There are cases, however, where in the recipe you
might need to set variables or override some default behavior.
Any
Metadata
[http://www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#metadata]
usually found in a recipe can also be placed in a class file. Class files are identified by the extension
.bbclass and are usually placed in a classes/ directory beneath the meta*/ directory found
in the Source Directory [http://www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#sourcedirectory]. Class files can also be pointed to by BUILDDIR (e.g. build/) in the same way as .conf
files in the conf directory. Class files are searched for in BBPATH using the same method by which
.conf files are searched.
This chapter discusses only the most useful and important classes. Other classes do exist within
the meta/classes directory in the Source Directory [http://www.yoctoproject.org/docs/1.8/devmanual/dev-manual.html#source-directory]. You can reference the .bbclass files directly for more
information.

7.1. allarch.bbclass
The allarch class is inherited by recipes that do not produce architecture-specific output. The class
disables functionality that is normally needed for recipes that produce executable binaries (such as
building the cross-compiler and a C library as pre-requisites, and splitting out of debug symbols during
packaging).
By default, all recipes inherit the base and package classes, which enable functionality needed for
recipes that produce executable output. If your recipe, for example, only produces packages that
contain configuration files, media files, or scripts (e.g. Python and Perl), then it should inherit the
allarch class.

7.2. archiver.bbclass
The archiver class supports releasing source code and other materials with the binaries.
For more details on the source archiver, see the "Maintaining Open Source License
Compliance During Your Product's Lifecycle [http://www.yoctoproject.org/docs/1.8/dev-manual/devmanual.html#maintaining-open-source-license-compliance-during-your-products-lifecycle]" section
in the Yocto Project Development Manual.

7.3. autotools.bbclass
The autotools class supports Autotooled packages.
The autoconf, automake, and libtool bring standardization. This class defines a set of
tasks (configure, compile etc.) that work for all Autotooled packages. It should usually be
enough to define a few standard variables and then simply inherit
autotools. This
class can also work with software that emulates Autotools. For more information, see
the "Autotooled Package [http://www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#newrecipe-autotooled-package]" section in the Yocto Project Development Manual.
By default, the autotools class uses out-of-tree builds (B != S). If the software being built by a
recipe does not support using out-of-tree builds, you should have the recipe inherit the autotoolsbrokensep class.
It's useful to have some idea of how the tasks defined by this class work and what they do behind
the scenes.
• do_configure # Regenerates the configure script (using autoreconf) and then launches it with a
standard set of arguments used during cross-compilation. You can pass additional parameters to
configure through the EXTRA_OECONF variable.

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Classes

• do_compile # Runs make with arguments that specify the compiler and linker. You can pass
additional arguments through the EXTRA_OEMAKE variable.
• do_install # Runs make install and passes in ${D} as DESTDIR.

7.4. autotools-brokensep.bbclass
The autotools-brokensep class behaves the same as the autotools class but builds with B == S.
This method is useful when out-of-tree build support is either not present or is broken.

Note
It is recommended that out-of-tree support be fixed and used if at all possible.

7.5. base.bbclass
The base class is special in that every .bb file implicitly inherits the class. This class contains
definitions for standard basic tasks such as fetching, unpacking, configuring (empty by default),
compiling (runs any Makefile present), installing (empty by default) and packaging (empty by
default). These classes are often overridden or extended by other classes such as the autotools class
or the package class. The class also contains some commonly used functions such as oe_runmake.

7.6. bin_package.bbclass
The bin_package class is a helper class for recipes that extract the contents of a binary package (e.g.
an RPM) and install those contents rather than building the binary from source. The binary package
is extracted and new packages in the configured output package format are created. Extraction and
installation of proprietary binaries is a good example use for this class.

Note
For RPMs and other packages that do not contain a subdirectory, you should specify a "subdir"
parameter. Here is an example where ${BP} is used so that the files are extracted into the
subdirectory expected by the default value of S:
SRC_URI = "http://example.com/downloads/somepackage.rpm;subdir=${BP}"

7.7. binconfig.bbclass
The binconfig class helps to correct paths in shell scripts.
Before pkg-config had become widespread, libraries shipped shell scripts to give information about
the libraries and include paths needed to build software (usually named LIBNAME-config). This class
assists any recipe using such scripts.
During staging, the OpenEmbedded build system installs such scripts into the sysroots/ directory.
Inheriting this class results in all paths in these scripts being changed to point into the sysroots/
directory so that all builds that use the script use the correct directories for the cross compiling layout.
See the BINCONFIG_GLOB variable for more information.

7.8. binconfig-disabled.bbclass
An alternative version of the binconfig class, which disables binary configuration scripts by making
them return an error in favor of using pkg-config to query the information. The scripts to be disabled
should be specified using the BINCONFIG variable within the recipe inheriting the class.

7.9. blacklist.bbclass
The blacklist class prevents the OpenEmbedded build system from building specific recipes
(blacklists them). To use this class, inherit the class globally and set PNBLACKLIST for each recipe
you wish to blacklist. Specify the PN value as a variable flag (varflag) and provide a reason, which is

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Classes

reported, if the package is requested to be built as the value. For example, if you want to blacklist a
recipe called "exoticware", you add the following to your local.conf or distribution configuration:
INHERIT += "blacklist"
PNBLACKLIST[exoticware] = "Not supported by our organization."

7.10. boot-directdisk.bbclass
The boot-directdisk class creates an image that can be placed directly onto a hard disk using dd
and then booted. The image uses SYSLINUX.
The end result is a 512 boot sector populated with a Master Boot Record (MBR) and partition table
followed by an MSDOS FAT16 partition containing SYSLINUX and a Linux kernel completed by the
ext2 and ext3 root filesystems.

7.11. bootimg.bbclass
The bootimg class creates a bootable image using SYSLINUX, your kernel, and an optional initial RAM
disk (initrd).
When you use this class, two things happen:
• A .hddimg file is created. This file is an MSDOS filesystem that contains SYSLINUX, a kernel, an
initrd, and a root filesystem image. All three of these can be written to hard drives directly and
also booted on a USB flash disks using dd.
• A CD .iso image is created. When this file is booted, the initrd boots and processes the label
selected in SYSLINUX. Actions based on the label are then performed (e.g. installing to a hard drive).
The bootimg class supports the INITRD, NOISO, NOHDD, and ROOTFS variables.

7.12. bugzilla.bbclass
The bugzilla class supports setting up an instance of Bugzilla in which you can automatically files
bug reports in response to build failures. For this class to work, you need to enable the XML-RPC
interface in the instance of Bugzilla.

7.13. buildhistory.bbclass
The buildhistory class records a history of build output metadata, which can be used to detect
possible regressions as well as used for analysis of the build output. For more information on using
Build History, see the "Maintaining Build Output Quality" section.

7.14. buildstats.bbclass
The buildstats class records performance statistics about each task executed during the build (e.g.
elapsed time, CPU usage, and I/O usage).
When you use this class, the output goes into the BUILDSTATS_BASE directory, which defaults
to ${TMPDIR}/buildstats/. You can analyze the elapsed time using scripts/pybootchartgui/
pybootchartgui.py, which produces a cascading chart of the entire build process and can be useful
for highlighting bottlenecks.
Collecting build statistics is enabled by default through the USER_CLASSES variable from your
local.conf file. Consequently, you do not have to do anything to enable the class. However, if you
want to disable the class, simply remove "buildstats" from the USER_CLASSES list.

7.15. buildstats-summary.bbclass
When inherited globally, prints statistics at the end of the build on sstate re-use. In order to function,
this class requires the buildstats class be enabled.

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Classes

7.16. ccache.bbclass
The ccache class enables the C/C++ Compiler Cache [http://ccache.samba.org/] for the build. This
class is used to give a minor performance boost during the build. However, using the class can
lead to unexpected side-effects. Thus, it is recommended that you do not use this class. See http://
ccache.samba.org/ for information on the C/C++ Compiler Cache.

7.17. chrpath.bbclass
The chrpath class is a wrapper around the "chrpath" utility, which is used during the build process
for nativesdk, cross, and cross-canadian recipes to change RPATH records within binaries in order
to make them relocatable.

7.18. clutter.bbclass
The clutter class consolidates the major and minor version naming and other common items used
by Clutter and related recipes.

Note
Unlike some other classes related to specific libraries, recipes building other software that
uses Clutter do not need to inherit this class unless they use the same recipe versioning
scheme that the Clutter and related recipes do.

7.19. cmake.bbclass
The cmake class allows for recipes that need to build software using the CMake build system. You
can use the EXTRA_OECMAKE variable to specify additional configuration options to be passed on the
cmake command line.

7.20. cml1.bbclass
The cml1 class provides basic support for the Linux kernel style build configuration system.

7.21. compress_doc.bbclass
Enables compression for man pages and info pages. This class is intended to be inherited globally.
The default compression mechanism is gz (gzip) but you can select an alternative mechanism by
setting the DOC_COMPRESS variable.

7.22. copyleft_compliance.bbclass
The copyleft_compliance class preserves source code for the purposes of license compliance. This
class is an alternative to the archiver class and is still used by some users even though it has been
deprecated in favor of the archiver class.

7.23. copyleft_filter.bbclass
A class used by the archiver and copyleft_compliance classes for filtering licenses. The
copyleft_filter class is an internal class and is not intended to be used directly.

7.24. core-image.bbclass
The core-image class provides common definitions for the core-image-* image recipes, such as
support for additional IMAGE_FEATURES.

7.25. cpan.bbclass
The cpan class supports Perl modules.

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Recipes for Perl modules are simple. These recipes usually only need to point to the source's archive
and then inherit the proper class file. Building is split into two methods depending on which method
the module authors used.
• Modules that use old Makefile.PL-based build system require cpan.bbclass in their recipes.
• Modules that use Build.PL-based build system require using cpan_build.bbclass in their recipes.

7.26. cross.bbclass
The cross class provides support for the recipes that build the cross-compilation tools.

7.27. cross-canadian.bbclass
The cross-canadian class provides support for the recipes that build the Canadian Cross-compilation
tools for SDKs. See the "Cross-Development Toolchain Generation" section for more discussion on
these cross-compilation tools.

7.28. crosssdk.bbclass
The crosssdk class provides support for the recipes that build the cross-compilation tools used for
building SDKs. See the "Cross-Development Toolchain Generation" section for more discussion on
these cross-compilation tools.

7.29. debian.bbclass
The debian class renames output packages so that they follow the Debian naming policy (i.e. eglibc
becomes libc6 and eglibc-devel becomes libc6-dev.) Renaming includes the library name and
version as part of the package name.
If a recipe creates packages for multiple libraries (shared object files of .so type), use the
LEAD_SONAME variable in the recipe to specify the library on which to apply the naming scheme.

7.30. deploy.bbclass
The deploy class handles deploying files to the DEPLOY_DIR_IMAGE directory. The main function of
this class is to allow the deploy step to be accelerated by shared state. Recipes that inherit this class
should define their own do_deploy function to copy the files to be deployed to DEPLOYDIR, and use
addtask to add the task at the appropriate place, which is usually after do_compile or do_install.
The class then takes care of staging the files from DEPLOYDIR to DEPLOY_DIR_IMAGE.

7.31. devshell.bbclass
The devshell class adds the do_devshell task. Distribution policy dictates whether to include this
class. See the "Using a Development Shell [http://www.yoctoproject.org/docs/1.8/dev-manual/devmanual.html#platdev-appdev-devshell]" section in the Yocto Project Development Manual for more
information about using devshell.

7.32. distro_features_check.bbclass
The distro_features_check class allows individual recipes to check for required and conflicting
DISTRO_FEATURES.
This class provides support for the REQUIRED_DISTRO_FEATURES and CONFLICT_DISTRO_FEATURES
variables. If any conditions specified in the recipe using the above variables are not met, the recipe
will be skipped.

7.33. distrodata.bbclass
The distrodata class provides for automatic checking for upstream recipe updates. The class
creates a comma-separated value (CSV) spreadsheet that contains information about the recipes. The

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information provides the do_distrodata and do_distro_check tasks, which do upstream checking
and also verify if a package is used in multiple major distributions.
The class is not included by default. To use it, you must include the following files and set the INHERIT
variable:
include conf/distro/include/distro_alias.inc
include conf/distro/include/recipe_color.inc
include conf/distro/include/maintainers.inc
include conf/distro/include/upstream_tracking.inc
include conf/distro/include/package_regex.inc
INHERIT+= "distrodata"

7.34. distutils.bbclass
The distutils class supports recipes for Python version 2.x extensions, which are simple. These
recipes usually only need to point to the source's archive and then inherit the proper class. Building
is split into two methods depending on which method the module authors used.
• Extensions that use an Autotools-based build system require Autotools and distutils-based
classes in their recipes.
• Extensions that use build systems based on distutils require the distutils class in their recipes.
• Extensions that use build systems based on setuptools require the setuptools class in their
recipes.

7.35. distutils3.bbclass
The distutils3 class supports recipes for Python version 3.x extensions, which are simple. These
recipes usually only need to point to the source's archive and then inherit the proper class. Building
is split into two methods depending on which method the module authors used.
• Extensions that use an Autotools-based build system require Autotools and distutils-based
classes in their recipes.
• Extensions that use distutils-based build systems require the distutils class in their recipes.
• Extensions that use build systems based on setuptools3 require the setuptools3 class in their
recipes.

7.36. externalsrc.bbclass
The externalsrc class supports building software from source code that is external to the
OpenEmbedded build system. Building software from an external source tree means that the build
system's normal fetch, unpack, and patch process is not used.
By default, the OpenEmbedded build system uses the S and B variables to locate unpacked recipe
source code and to build it, respectively. When your recipe inherits the externalsrc class, you use
the EXTERNALSRC and EXTERNALSRC_BUILD variables to ultimately define S and B.
By default, this class expects the source code to support recipe builds that use the B variable to
point to the directory in which the OpenEmbedded build system places the generated objects built
from the recipes. By default, the B directory is set to the following, which is separate from the source
directory (S):
${WORKDIR}/${BPN}/{PV}/
See these variables for more information: WORKDIR, BPN, and PV,
For more information on the externalsrc class, see the comments in meta/classes/
externalsrc.bbclass in the Source Directory [http://www.yoctoproject.org/docs/1.8/dev-manual/

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dev-manual.html#source-directory]. For information on how to use the externalsrc class, see the
"Building Software from an External Source [http://www.yoctoproject.org/docs/1.8/dev-manual/devmanual.html#building-software-from-an-external-source]" section in the Yocto Project Development
Manual.

7.37. extrausers.bbclass
The extrausers class allows additional user and group configuration to be applied at the image
level. Inheriting this class either globally or from an image recipe allows additional user and group
operations to be performed using the EXTRA_USERS_PARAMS variable.

Note
The user and group operations added using the extrausers class are not tied to a specific
recipe outside of the recipe for the image. Thus, the operations can be performed across the
image as a whole. Use the useradd class to add user and group configuration to a specific
recipe.
Here is an example that uses this class in an image recipe:
inherit extrausers
EXTRA_USERS_PARAMS = "\
useradd -p '' tester; \
groupadd developers; \
userdel nobody; \
groupdel -g video; \
groupmod -g 1020 developers; \
usermod -s /bin/sh tester; \
"
Here is an example that adds two users named "tester-jim" and "tester-sue" and assigns passwords:
inherit extrausers
EXTRA_USERS_PARAMS = "\
useradd -P tester01 tester-jim; \
useradd -P tester01 tester-sue; \
"
Finally, here is an example that sets the root password to "1876*18":
inherit extrausers
EXTRA_USERS_PARAMS = "\
useradd -P 1876*18 root; \
"

7.38. fontcache.bbclass
The fontcache class generates the proper post-install and post-remove (postinst and postrm)
scriptlets for font packages. These scriptlets call fc-cache (part of Fontconfig) to add the fonts to
the font information cache. Since the cache files are architecture-specific, fc-cache runs using QEMU
if the postinst scriptlets need to be run on the build host during image creation.
If the fonts being installed are in packages other than the main package, set FONT_PACKAGES to specify
the packages containing the fonts.

7.39. gconf.bbclass
The gconf class provides common functionality for recipes that need to install GConf schemas. The
schemas will be put into a separate package (${PN}-gconf) that is created automatically when this

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class is inherited. This package uses the appropriate post-install and post-remove (postinst/postrm)
scriptlets to register and unregister the schemas in the target image.

7.40. gettext.bbclass
The gettext class provides support for building software that uses the GNU gettext
internationalization and localization system. All recipes building software that use gettext should
inherit this class.

7.41. gnome.bbclass
The gnome class supports recipes that build software from the GNOME stack. This class inherits the
gnomebase, gtk-icon-cache, gconf and mime classes. The class also disables GObject introspection
where applicable.

7.42. gnomebase.bbclass
The gnomebase class is the base class for recipes that build software from the GNOME stack. This
class sets SRC_URI to download the source from the GNOME mirrors as well as extending FILES with
the typical GNOME installation paths.

7.43. grub-efi.bbclass
The grub-efi class provides grub-efi-specific functions for building bootable images.
This class supports several variables:
• INITRD: Indicates list of filesystem images to concatenate and use as an initial RAM disk (initrd)
(optional).
• ROOTFS: Indicates a filesystem image to include as the root filesystem (optional).
• GRUB_GFXSERIAL: Set this to "1" to have graphics and serial in the boot menu.
• LABELS: A list of targets for the automatic configuration.
• APPEND: An override list of append strings for each LABEL.
• GRUB_OPTS: Additional options to add to the configuration (optional). Options are delimited using
semi-colon characters (;).
• GRUB_TIMEOUT: Timeout before executing the default LABEL (optional).

7.44. gsettings.bbclass
The gsettings class provides common functionality for recipes that need to install GSettings (glib)
schemas. The schemas are assumed to be part of the main package. Appropriate post-install and
post-remove (postinst/postrm) scriptlets are added to register and unregister the schemas in the
target image.

7.45. gtk-doc.bbclass
The gtk-doc class is a helper class to pull in the appropriate gtk-doc dependencies and disable gtkdoc.

7.46. gtk-icon-cache.bbclass
The gtk-icon-cache class generates the proper post-install and post-remove (postinst/postrm)
scriptlets for packages that use GTK+ and install icons. These scriptlets call gtk-update-icon-cache
to add the fonts to GTK+'s icon cache. Since the cache files are architecture-specific, gtk-update-

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Classes

icon-cache is run using QEMU if the postinst scriptlets need to be run on the build host during image
creation.

7.47. gtk-immodules-cache.bbclass
The gtk-immodules-cache class generates the proper post-install and post-remove (postinst/postrm)
scriptlets for packages that install GTK+ input method modules for virtual keyboards. These scriptlets
call gtk-update-icon-cache to add the input method modules to the cache. Since the cache files
are architecture-specific, gtk-update-icon-cache is run using QEMU if the postinst scriptlets need
to be run on the build host during image creation.
If the input method modules being installed are in packages other than the main package, set
GTKIMMODULES_PACKAGES to specify the packages containing the modules.

7.48. gummiboot.bbclass
The gummiboot class provides functions specific to the gummiboot bootloader for building bootable
images. This is an internal class and is not intended to be used directly. Set the EFI_PROVIDER variable
to "gummiboot" to use this class.
For information on more variables used and supported in this class, see the GUMMIBOOT_CFG,
GUMMIBOOT_ENTRIES, and GUMMIBOOT_TIMEOUT variables.
You can also see the Gummiboot documentation [http://freedesktop.org/wiki/Software/gummiboot/]
for more information.

7.49. gzipnative.bbclass
The gzipnative class enables the use of native versions of gzip and pigz rather than the versions
of these tools from the build host.

7.50. icecc.bbclass
The icecc class supports Icecream [https://github.com/icecc/icecream], which facilitates taking
compile jobs and distributing them among remote machines.
The class stages directories with symlinks from gcc and g++ to icecc, for both native and cross
compilers. Depending on each configure or compile, the OpenEmbedded build system adds the
directories at the head of the PATH list and then sets the ICECC_CXX and ICEC_CC variables, which
are the paths to the g++ and gcc compilers, respectively.
For the cross compiler, the class creates a tar.gz file that contains the Yocto Project toolchain and sets
ICECC_VERSION, which is the version of the cross-compiler used in the cross-development toolchain,
accordingly.
The class handles all three different compile stages (i.e native ,cross-kernel and target) and creates
the necessary environment tar.gz file to be used by the remote machines. The class also supports
SDK generation.
If ICECC_PATH is not set in your local.conf file, then the class tries to locate the icecc binary using
which. If ICECC_ENV_EXEC is set in your local.conf file, the variable should point to the icecccreate-env script provided by the user. If you do not point to a user-provided script, the build system
uses the default script provided by the recipe icecc-create-env-native.bb.

Note
This script is a modified version and not the one that comes with icecc.
If you do not want the Icecream distributed compile support to apply to specific recipes or classes, you
can effectively "blacklist" them by listing the recipes and classes using the ICECC_USER_PACKAGE_BL
and ICECC_USER_CLASS_BL, variables, respectively, in your local.conf file. Doing so causes the
OpenEmbedded build system to handle these compilations locally.
Additionally, you can list recipes using the ICECC_USER_PACKAGE_WL variable in your local.conf file
to force icecc to be enabled for recipes using an empty PARALLEL_MAKE variable.

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Inheriting the icecc class changes all sstate signatures. Consequently, if a development team
has a dedicated build system that populates STATE_MIRRORS and they want to reuse sstate from
STATE_MIRRORS, then all developers and the build system need to either inherit the icecc class or
nobody should.
At the distribution level, you can inherit the icecc class to be sure that all builders start with the
same sstate signatures. After inheriting the class, you can then disable the feature by setting the
ICECC_DISABLED variable to "1" as follows:
INHERIT_DISTRO += "icecc"
ICECC_DISABLED ??= "1"
This practice makes sure everyone is using the same signatures but also requires individuals that do
want to use Icecream to enable the feature individually as follows in your local.conf file:
ICECC_DISABLED = ""

7.51. image.bbclass
The image class helps support creating images in different formats. First, the root filesystem is created
from packages using one of the rootfs*.bbclass files (depending on the package format used) and
then one or more image files are created.
• The IMAGE_FSTYPES variable controls the types of images to generate.
• The IMAGE_INSTALL variable controls the list of packages to install into the image.
For information on customizing images, see the "Customizing Images [http://www.yoctoproject.org/
docs/1.8/dev-manual/dev-manual.html#usingpoky-extend-customimage]" section in the Yocto
Project Development Manual. For information on how images are created, see the "Images" section
elsewhere in this manual.

7.52. image_types.bbclass
The image_types class defines all of the standard image output types that you can enable through
the IMAGE_FSTYPES variable. You can use this class as a reference on how to add support for custom
image output types.
By default, this class is enabled through the IMAGE_CLASSES variable in image.bbclass. If you define
your own image types using a custom BitBake class and then use IMAGE_CLASSES to enable it, the
custom class must either inherit image_types or image_types must also appear in IMAGE_CLASSES.

7.53. image_types_uboot.bbclass
The image_types_uboot class defines additional image types specifically for the U-Boot bootloader.

7.54. image-live.bbclass
The image-live class supports building "live" images.
Normally, you do not use this class directly. Instead, you add "live" to IMAGE_FSTYPES. For example,
if you were building an ISO image, you would add "live" to IMAGE_FSTYPES, set the NOISO variable to
"0" and the build system would use the image-live class to build the ISO image.

7.55. image-mklibs.bbclass
The image-mklibs class enables the use of the mklibs utility during the do_rootfs task, which
optimizes the size of libraries contained in the image.

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By default, the class is enabled in the local.conf.template using the USER_CLASSES variable as
follows:
USER_CLASSES ?= "buildstats image-mklibs image-prelink"

7.56. image-prelink.bbclass
The image-prelink class enables the use of the prelink utility during the do_rootfs task, which
optimizes the dynamic linking of shared libraries to reduce executable startup time.
By default, the class is enabled in the local.conf.template using the USER_CLASSES variable as
follows:
USER_CLASSES ?= "buildstats image-mklibs image-prelink"

7.57. image-swab.bbclass
The image-swab class enables the Swabber [http://www.yoctoproject.org/tools-resources/projects/
swabber] tool in order to detect and log accesses to the host system during the OpenEmbedded build
process.

Note
This class is currently unmaintained.

7.58. image-vmdk.bbclass
The image-vmdk class supports building VMware VMDK images. Normally, you do not use this class
directly. Instead, you add "vmdk" to IMAGE_FSTYPES.

7.59. insane.bbclass
The insane class adds a step to the package generation process so that output quality assurance
checks are generated by the OpenEmbedded build system. A range of checks are performed that
check the build's output for common problems that show up during runtime. Distribution policy usually
dictates whether to include this class.
You can configure the sanity checks so that specific test failures either raise a warning or an error
message. Typically, failures for new tests generate a warning. Subsequent failures for the same test
would then generate an error message once the metadata is in a known and good condition. See the
"QA Error and Warning Messages" Chapter for a list of all the warning and error messages you might
encounter using a default configuration.
Use the WARN_QA and ERROR_QA variables to control the behavior of these checks at the global level
(i.e. in your custom distro configuration). However, to skip one or more checks in recipes, you should
use INSANE_SKIP. For example, to skip the check for symbolic link .so files in the main package of
a recipe, add the following to the recipe. You need to realize that the package name override, in this
example ${PN}, must be used:
INSANE_SKIP_${PN} += "dev-so"
Please keep in mind that the QA checks exist in order to detect real or potential problems in the
packaged output. So exercise caution when disabling these checks.
The following list shows the tests you can list with the WARN_QA and ERROR_QA variables:
• already-stripped: Checks that produced binaries have not already been stripped prior to the
build system extracting debug symbols. It is common for upstream software projects to default to

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stripping debug symbols for output binaries. In order for debugging to work on the target using dbg packages, this stripping must be disabled.
• arch: Checks the Executable and Linkable Format (ELF) type, bit size, and endianness of any
binaries to ensure they match the target architecture. This test fails if any binaries do not match
the type since there would be an incompatibility. The test could indicate that the wrong compiler
or compiler options have been used. Sometimes software, like bootloaders, might need to bypass
this check.
• buildpaths: Checks for paths to locations on the build host inside the output files. Currently, this
test triggers too many false positives and thus is not normally enabled.
• build-deps: Determines if a build-time dependency that is specified through DEPENDS, explicit
RDEPENDS, or task-level dependencies exists to match any runtime dependency. This determination
is particularly useful to discover where runtime dependencies are detected and added during
packaging. If no explicit dependency has been specified within the metadata, at the packaging
stage it is too late to ensure that the dependency is built, and thus you can end up with an
error when the package is installed into the image during the do_rootfs task because the autodetected dependency was not satisfied. An example of this would be where the update-rc.d
class automatically adds a dependency on the initscripts-functions package to packages that
install an initscript that refers to /etc/init.d/functions. The recipe should really have an explicit
RDEPENDS for the package in question on initscripts-functions so that the OpenEmbedded build
system is able to ensure that the initscripts recipe is actually built and thus the initscriptsfunctions package is made available.
• compile-host-path: Checks the do_compile log for indications that paths to locations on the build
host were used. Using such paths might result in host contamination of the build output.
• debug-deps: Checks that all packages except -dbg packages do not depend on -dbg packages,
which would cause a packaging bug.
• debug-files: Checks for .debug directories in anything but the -dbg package. The debug files
should all be in the -dbg package. Thus, anything packaged elsewhere is incorrect packaging.
• dep-cmp: Checks for invalid version comparison statements in runtime dependency relationships
between packages (i.e. in RDEPENDS, RRECOMMENDS, RSUGGESTS, RPROVIDES, RREPLACES, and
RCONFLICTS variable values). Any invalid comparisons might trigger failures or undesirable behavior
when passed to the package manager.
• desktop: Runs the desktop-file-validate program against any .desktop files to validate their
contents against the specification for .desktop files.
• dev-deps: Checks that all packages except -dev or -staticdev packages do not depend on -dev
packages, which would be a packaging bug.
• dev-so: Checks that the .so symbolic links are in the -dev package and not in any of the other
packages. In general, these symlinks are only useful for development purposes. Thus, the -dev
package is the correct location for them. Some very rare cases do exist for dynamically loaded
modules where these symlinks are needed instead in the main package.
• file-rdeps: Checks that file-level dependencies identified by the OpenEmbedded build system
at packaging time are satisfied. For example, a shell script might start with the line #!/bin/bash.
This line would translate to a file dependency on /bin/bash. Of the three package managers
that the OpenEmbedded build system supports, only RPM directly handles file-level dependencies,
resolving them automatically to packages providing the files. However, the lack of that functionality
in the other two package managers does not mean the dependencies do not still need resolving.
This QA check attempts to ensure that explicitly declared RDEPENDS exist to handle any file-level
dependency detected in packaged files.
• files-invalid: Checks for FILES variable values that contain "//", which is invalid.
• incompatible-license: Report when packages are excluded from being created due to being
marked with a license that is in INCOMPATIBLE_LICENSE.
• install-host-path: Checks the do_install log for indications that paths to locations on the build
host were used. Using such paths might result in host contamination of the build output.

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• installed-vs-shipped: Reports when files have been installed within do_install but have not
been included in any package by way of the FILES variable. Files that do not appear in any package
cannot be present in an image later on in the build process. Ideally, all installed files should be
packaged or not installed at all. These files can be deleted at the end of do_install if the files
are not needed in any package.
• la: Checks .la files for any TMPDIR paths. Any .la file containing these paths is incorrect since
libtool adds the correct sysroot prefix when using the files automatically itself.
• ldflags: Ensures that the binaries were linked with the LDFLAGS options provided by the build
system. If this test fails, check that the LDFLAGS variable is being passed to the linker command.
• libdir: Checks for libraries being installed into incorrect (possibly hardcoded) installation paths.
For example, this test will catch recipes that install /lib/bar.so when ${base_libdir} is "lib32".
Another example is when recipes install /usr/lib64/foo.so when ${libdir} is "/usr/lib".
• libexec: Checks if a package contains files in /usr/libexec. This check is not performed if the
libexecdir variable has been set explicitly to /usr/libexec.
• packages-list: Checks for the same package being listed multiple times through the PACKAGES
variable value. Installing the package in this manner can cause errors during packaging.
• perm-config: Reports lines in fs-perms.txt that have an invalid format.
• perm-line: Reports lines in fs-perms.txt that have an invalid format.
• perm-link: Reports lines in fs-perms.txt that specify 'link' where the specified target already
exists.
• perms: Currently, this check is unused but reserved.
• pkgconfig: Checks .pc files for any TMPDIR/WORKDIR paths. Any .pc file containing these paths is
incorrect since pkg-config itself adds the correct sysroot prefix when the files are accessed.
• pkgname: Checks that all packages in PACKAGES have names that do not contain invalid characters
(i.e. characters other than 0-9, a-z, ., +, and -).
• pkgv-undefined: Checks to see if the PKGV variable is undefined during do_package.
• pkgvarcheck: Checks through the variables RDEPENDS, RRECOMMENDS, RSUGGESTS, RCONFLICTS,
RPROVIDES, RREPLACES, FILES, ALLOW_EMPTY, pkg_preinst, pkg_postinst, pkg_prerm and
pkg_postrm, and reports if there are variable sets that are not package-specific. Using
these variables without a package suffix is bad practice, and might unnecessarily complicate
dependencies of other packages within the same recipe or have other unintended consequences.
• pn-overrides: Checks that a recipe does not have a name (PN) value that appears in OVERRIDES. If
a recipe is named such that its PN value matches something already in OVERRIDES (e.g. PN happens
to be the same as MACHINE or DISTRO), it can have unexpected consequences. For example,
assignments such as FILES_${PN} = "xyz" effectively turn into FILES = "xyz".
• rpaths: Checks for rpaths in the binaries that contain build system paths such as TMPDIR. If this
test fails, bad -rpath options are being passed to the linker commands and your binaries have
potential security issues.
• split-strip: Reports that splitting or stripping debug symbols from binaries has failed.
• staticdev: Checks for static library files (*.a) in non-staticdev packages.
• symlink-to-sysroot: Checks for symlinks in packages that point into TMPDIR on the host. Such
symlinks will work on the host, but are clearly invalid when running on the target.
• textrel: Checks for ELF binaries that contain relocations in their .text sections, which can result
in a performance impact at runtime.
• unsafe-references-in-binaries: Reports when a binary installed in ${base_libdir},
${base_bindir}, or ${base_sbindir}, depends on another binary installed under
${exec_prefix}. This dependency is a concern if you want the system to remain basically operable
if /usr is mounted separately and is not mounted.

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Note
Defaults for binaries installed in ${base_libdir}, ${base_bindir}, and ${base_sbindir}
are /lib, /bin, and /sbin, respectively. The default for a binary installed under
${exec_prefix} is /usr.
• unsafe-references-in-scripts: Reports when a script file installed in ${base_libdir},
${base_bindir}, or ${base_sbindir}, depends on files installed under ${exec_prefix}. This
dependency is a concern if you want the system to remain basically operable if /usr is mounted
separately and is not mounted.

Note
Defaults for binaries installed in ${base_libdir}, ${base_bindir}, and ${base_sbindir}
are /lib, /bin, and /sbin, respectively. The default for a binary installed under
${exec_prefix} is /usr.
• useless-rpaths: Checks for dynamic library load paths (rpaths) in the binaries that by default on
a standard system are searched by the linker (e.g. /lib and /usr/lib). While these paths will not
cause any breakage, they do waste space and are unnecessary.
• var-undefined: Reports when variables fundamental to packaging (i.e. WORKDIR, DEPLOY_DIR, D,
PN, and PKGD) are undefined during do_package.
• version-going-backwards: If Build History is enabled, reports when a package being written out
has a lower version than the previously written package under the same name. If you are placing
output packages into a feed and upgrading packages on a target system using that feed, the version
of a package going backwards can result in the target system not correctly upgrading to the "new"
version of the package.

Note
If you are not using runtime package management on your target system, then you do not
need to worry about this situation.
• xorg-driver-abi: Checks that all packages containing Xorg drivers have ABI dependencies. The
xserver-xorg recipe provides driver ABI names. All drivers should depend on the ABI versions
that they have been built against. Driver recipes that include xorg-driver-input.inc or xorgdriver-video.inc will automatically get these versions. Consequently, you should only need to
explicitly add dependencies to binary driver recipes.

7.60. insserv.bbclass
The insserv class uses the insserv utility to update the order of symbolic links in /etc/rc?.d/
within an image based on dependencies specified by LSB headers in the init.d scripts themselves.

7.61. kernel.bbclass
The kernel class handles building Linux kernels. The class contains code to build all kernel trees.
All needed headers are staged into the STAGING_KERNEL_DIR directory to allow out-of-tree module
builds using the module class.
This means that each built kernel module is packaged separately and inter-module dependencies
are created by parsing the modinfo output. If all modules are required, then installing the kernelmodules package installs all packages with modules and various other kernel packages such as
kernel-vmlinux.
Various other classes are used by the kernel and module classes internally including the kernelarch, module-base, and linux-kernel-base classes.

7.62. kernel-arch.bbclass
The kernel-arch class sets the ARCH environment variable for Linux kernel compilation (including
modules).

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7.63. kernel-module-split.bbclass
The kernel-module-split class provides common functionality for splitting Linux kernel modules
into separate packages.

7.64. kernel-yocto.bbclass
The kernel-yocto class provides common functionality for building from linux-yocto style kernel
source repositories.

7.65. lib_package.bbclass
The lib_package class supports recipes that build libraries and produce executable binaries, where
those binaries should not be installed by default along with the library. Instead, the binaries are added
to a separate ${PN}-bin package to make their installation optional.

7.66. license.bbclass
The license class provides license manifest creation and license exclusion. This class is enabled by
default using the default value for the INHERIT_DISTRO variable.

7.67. linux-kernel-base.bbclass
The linux-kernel-base class provides common functionality for recipes that build out of the Linux
kernel source tree. These builds goes beyond the kernel itself. For example, the Perf recipe also
inherits this class.

7.68. logging.bbclass
The logging class provides the standard shell functions used to log messages for various BitBake
severity levels (i.e. bbplain, bbnote, bbwarn, bberror, bbfatal, and bbdebug).
This class is enabled by default since it is inherited by the base class.

7.69. meta.bbclass
The meta class is inherited by recipes that do not build any output packages themselves, but act as
a "meta" target for building other recipes.

7.70. metadata_scm.bbclass
The metadata_scm class provides functionality for querying the branch and revision of a Source Code
Manager (SCM) repository.
The base class uses this class to print the revisions of each layer before starting every build. The
metadata_scm class is enabled by default because it is inherited by the base class.

7.71. mime.bbclass
The mime class generates the proper post-install and post-remove (postinst/postrm) scriptlets for
packages that install MIME type files. These scriptlets call update-mime-database to add the MIME
types to the shared database.

7.72. mirrors.bbclass
The mirrors class sets up some standard MIRRORS entries for source code mirrors. These mirrors
provide a fall-back path in case the upstream source specified in SRC_URI within recipes is unavailable.

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This class is enabled by default since it is inherited by the base class.

7.73. module.bbclass
The module class provides support for building out-of-tree Linux kernel modules. The class inherits the
module-base and kernel-module-split classes, and implements the do_compile and do_install
tasks. The class provides everything needed to build and package a kernel module.
For general information on out-of-tree Linux kernel modules, see the "Incorporating Out-of-Tree
Modules
[http://www.yoctoproject.org/docs/1.8/kernel-manual/kernel-manual.html#incorporatingout-of-tree-modules]" section in the Yocto Project Linux Kernel Development Manual.

7.74. module-base.bbclass
The module-base class provides the base functionality for building Linux kernel modules. Typically,
a recipe that builds software that includes one or more kernel modules and has its own means of
building the module inherits this class as opposed to inheriting the module class.

7.75. multilib*.bbclass
The multilib* classes provide support for building libraries with different target optimizations or
target architectures and installing them side-by-side in the same image.
For more information on using the Multilib feature, see the "Combining Multiple
Versions of Library Files into One Image [http://www.yoctoproject.org/docs/1.8/dev-manual/devmanual.html#combining-multiple-versions-library-files-into-one-image]" section in the Yocto Project
Development Manual.

7.76. native.bbclass
The native class provides common functionality for recipes that wish to build tools to run on the
build host (i.e. tools that use the compiler or other tools from the build host).
You can create a recipe that builds tools that run natively on the host a couple different ways:
• Create a myrecipe-native.bb that inherits the native class. If you use this method, you must
order the inherit statement in the recipe after all other inherit statements so that the native class
is inherited last.
• Create or modify a target recipe that contains the following:
BBCLASSEXTEND = "native"
Inside the recipe, use _class-native and _class-target overrides to specify any functionality
specific to the respective native or target case.
Although applied differently, the native class is used with both methods. The advantage of the
second method is that you do not need to have two separate recipes (assuming you need both) for
native and target. All common parts of the recipe are automatically shared.

7.77. nativesdk.bbclass
The nativesdk class provides common functionality for recipes that wish to build tools to run as part
of an SDK (i.e. tools that run on SDKMACHINE).
You can create a recipe that builds tools that run on the SDK machine a couple different ways:
• Create a myrecipe-nativesdk.bb recipe that inherits the nativesdk class. If you use this method,
you must order the inherit statement in the recipe after all other inherit statements so that the
nativesdk class is inherited last.

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• Create a nativesdk variant of any recipe by adding the following:
BBCLASSEXTEND = "nativesdk"
Inside the recipe, use _class-nativesdk and _class-target overrides to specify any functionality
specific to the respective SDK machine or target case.
Although applied differently, the nativesdk class is used with both methods. The advantage of the
second method is that you do not need to have two separate recipes (assuming you need both) for
the SDK machine and the target. All common parts of the recipe are automatically shared.

7.78. oelint.bbclass
The oelint class is an obsolete lint checking tool that exists in meta/classes in the Source Directory
[http://www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#source-directory].
A number of classes exist that are could be generally useful in OE-Core but are never actually used
within OE-Core itself. The oelint class is one such example. However, being aware of this class can
reduce the proliferation of different versions of similar classes across multiple layers.

7.79. own-mirrors.bbclass
The own-mirrors class makes it easier to set up your own PREMIRRORS from which to first fetch source
before attempting to fetch it from the upstream specified in SRC_URI within each recipe.
To use this class, inherit it globally and specify SOURCE_MIRROR_URL. Here is an example:
INHERIT += "own-mirrors"
SOURCE_MIRROR_URL = "http://example.com/my-source-mirror"
You can specify only a single URL in SOURCE_MIRROR_URL.

7.80. package.bbclass
The package class supports generating packages from a build's output. The core generic functionality
is in package.bbclass. The code specific to particular package types resides in these packagespecific classes: package_deb, package_rpm, package_ipk, and package_tar.
You can control the list of resulting package formats by using the PACKAGE_CLASSES variable
defined in your conf/local.conf configuration file, which is located in the Build Directory [http://
www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#build-directory]. When defining the
variable, you can specify one or more package types. Since images are generated from packages, a
packaging class is needed to enable image generation. The first class listed in this variable is used
for image generation.
If you take the optional step to set up a repository (package feed) on the development host that
can be used by Smart, you can install packages from the feed while you are running the image
on the target (i.e. runtime installation of packages). For more information, see the "Using Runtime
Package Management [http://www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#usingruntime-package-management]" section in the Yocto Project Development Manual.
The package-specific class you choose can affect build-time performance and has space ramifications.
In general, building a package with IPK takes about thirty percent less time as compared to using
RPM to build the same or similar package. This comparison takes into account a complete build of
the package with all dependencies previously built. The reason for this discrepancy is because the
RPM package manager creates and processes more Metadata [http://www.yoctoproject.org/docs/1.8/
dev-manual/dev-manual.html#metadata] than the IPK package manager. Consequently, you might
consider setting PACKAGE_CLASSES to "package_ipk" if you are building smaller systems.
Before making your package manager decision, however, you should consider some further things
about using RPM:

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Classes

• RPM starts to provide more abilities than IPK due to the fact that it processes more Metadata. For
example, this information includes individual file types, file checksum generation and evaluation on
install, sparse file support, conflict detection and resolution for Multilib systems, ACID style upgrade,
and repackaging abilities for rollbacks.
• For smaller systems, the extra space used for the Berkeley Database and the amount of metadata
when using RPM can affect your ability to perform on-device upgrades.
You can find additional information on the effects of the package class at these two Yocto Project
mailing list links:
• https://lists.yoctoproject.org/pipermail/poky/2011-May/006362.html
pipermail/poky/2011-May/006362.html]

[http://lists.yoctoproject.org/

• https://lists.yoctoproject.org/pipermail/poky/2011-May/006363.html
pipermail/poky/2011-May/006363.html]

[http://lists.yoctoproject.org/

7.81. package_deb.bbclass
The package_deb class provides support for creating packages that use the .deb file format. The
class ensures the packages are written out to the ${DEPLOY_DIR}/deb directory in a .deb file format.
This class inherits the package class and is enabled through the PACKAGE_CLASSES variable in the
local.conf file.

7.82. package_ipk.bbclass
The package_ipk class provides support for creating packages that use the .ipk file format. The
class ensures the packages are written out to the ${DEPLOY_DIR}/ipk directory in a .ipk file format.
This class inherits the package class and is enabled through the PACKAGE_CLASSES variable in the
local.conf file.

7.83. package_rpm.bbclass
The package_deb class provides support for creating packages that use the .rpm file format. The
class ensures the packages are written out to the ${DEPLOY_DIR}/rpm directory in a .rpm file format.
This class inherits the package class and is enabled through the PACKAGE_CLASSES variable in the
local.conf file.

7.84. package_tar.bbclass
The package_tar class provides support for creating packages that use the .tar file format. The
class ensures the packages are written out to the ${DEPLOY_DIR}/tar directory in a .tar file format.
This class inherits the package class and is enabled through the PACKAGE_CLASSES variable in the
local.conf file.

Note
You cannot specify the package_tar class first using the PACKAGE_CLASSES variable. You must
use .deb, .ipk, or .rpm file formats for your image or SDK.

7.85. packagedata.bbclass
The packagedata class provides common functionality for reading pkgdata files found in
PKGDATA_DIR. These files contain information about each output package produced by the
OpenEmbedded build system.
This class is enabled by default because it is inherited by the package class.

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7.86. packagegroup.bbclass
The packagegroup class sets default values appropriate for package group recipes (e.g. PACKAGES,
PACKAGE_ARCH, ALLOW_EMPTY, and so forth). It is highly recommended that all package group recipes
inherit this class.
For information on how to use this class, see the "Customizing Images Using Custom
Package Groups [http://www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#usingpokyextend-customimage-customtasks]" section in the Yocto Project Development Manual.
Previously, this class was called the task class.

7.87. packageinfo.bbclass
The packageinfo class gives a BitBake user interface the ability to retrieve information about output
packages from the pkgdata files.
This class is enabled automatically when using the Hob [http://www.yoctoproject.org/tools-resources/
projects/hob] user interface.

7.88. patch.bbclass
The patch class provides all functionality for applying patches during the do_patch task.
This class is enabled by default because it is inherited by the base class.

7.89. perlnative.bbclass
When inherited by a recipe, the perlnative class supports using the native version of Perl built by
the build system rather than using the version provided by the build host.

7.90. pixbufcache.bbclass
The pixbufcache class generates the proper post-install and post-remove (postinst/postrm) scriptlets
for packages that install pixbuf loaders, which are used with gdk-pixbuf. These scriptlets call
update_pixbuf_cache to add the pixbuf loaders to the cache. Since the cache files are architecturespecific, update_pixbuf_cache is run using QEMU if the postinst scriptlets need to be run on the
build host during image creation.
If the pixbuf loaders being installed are in packages other than the recipe's main package, set
PIXBUF_PACKAGES to specify the packages containing the loaders.

7.91. pkgconfig.bbclass
The pkg-config class provides a standard way to get header and library information. This class aims
to smooth integration of pkg-config into libraries that use it.
During staging, BitBake installs pkg-config data into the sysroots/ directory. By making use of
sysroot functionality within pkg-config, this class no longer has to manipulate the files.

7.92. populate_sdk.bbclass
The populate_sdk class provides support for SDK-only recipes. For information on advantages
gained when building a cross-development toolchain using the do_populate_sdk task, see
the "Optionally Building a Toolchain Installer [http://www.yoctoproject.org/docs/1.8/adt-manual/
adt-manual.html#optionally-building-a-toolchain-installer]" section in the Yocto Project Application
Developer's Guide.

7.93. populate_sdk_*.bbclass
The populate_sdk_* classes support SDK creation and consist of the following classes:

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Classes

• populate_sdk_base: The base class supporting SDK creation under all package managers (i.e. DEB,
RPM, and opkg).
• populate_sdk_deb: Supports creation of the SDK given the Debian package manager.
• populate_sdk_rpm: Supports creation of the SDK given the RPM package manager.
• populate_sdk_ipk: Supports creation of the SDK given the opkg (IPK format) package manager.
The populate_sdk_base class inherits the appropriate populate_sdk_* (i.e. deb, rpm, and ipk) based
on IMAGE_PKGTYPE.
The base class ensures all source and destination directories are established and then populates the
SDK. After populating the SDK, the populate_sdk_base class constructs two sysroots: ${SDK_ARCH}nativesdk, which contains the cross-compiler and associated tooling, and the target, which contains
a target root filesystem that is configured for the SDK usage. These two images reside in SDK_OUTPUT,
which consists of the following:
${SDK_OUTPUT}/${SDK_ARCH}-nativesdk-pkgs
${SDK_OUTPUT}/${SDKTARGETSYSROOT}/target-pkgs
Finally, the base populate SDK class creates the toolchain environment setup script, the tarball of
the SDK, and the installer.
The respective populate_sdk_deb, populate_sdk_rpm, and populate_sdk_ipk classes each support
the specific type of SDK. These classes are inherited by and used with the populate_sdk_base class.
For more information on the cross-development toolchain generation, see the "Cross-Development
Toolchain Generation" section. For information on advantages gained when building a crossdevelopment toolchain using the do_populate_sdk task, see the "Optionally Building a
Toolchain Installer [http://www.yoctoproject.org/docs/1.8/adt-manual/adt-manual.html#optionallybuilding-a-toolchain-installer]" section in the Yocto Project Application Developer's Guide.

7.94. prexport.bbclass
The prexport class provides functionality for exporting PR values.

Note
This class is not intended to be used directly. Rather, it is enabled when using "bitbakeprserv-tool export".

7.95. primport.bbclass
The primport class provides functionality for importing PR values.

Note
This class is not intended to be used directly. Rather, it is enabled when using "bitbakeprserv-tool import".

7.96. prserv.bbclass
The prserv class provides functionality for using a PR service [http://www.yoctoproject.org/docs/1.8/
dev-manual/dev-manual.html#working-with-a-pr-service] in order to automatically manage the
incrementing of the PR variable for each recipe.
This class is enabled by default because it is inherited by the package class. However, the
OpenEmbedded build system will not enable the functionality of this class unless PRSERV_HOST has
been set.

7.97. ptest.bbclass
The ptest class provides functionality for packaging and installing runtime tests for recipes that build
software that provides these tests.

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This class is intended to be inherited by individual recipes. However, the class' functionality is largely
disabled unless "ptest" appears in DISTRO_FEATURES. See the "Testing Packages With ptest [http://
www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#testing-packages-with-ptest]" section
in the Yocto Project Development Manual for more information on ptest.

7.98. ptest-gnome.bbclass
Enables package tests (ptests) specifically for GNOME packages, which have tests intended to be
executed with gnome-desktop-testing.
For information on setting up and running ptests, see the "Testing Packages With ptest [http://
www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#testing-packages-with-ptest]" section
in the Yocto Project Development Manual.

7.99. python-dir.bbclass
The python-dir class provides the base version, location, and site package location for Python.

7.100. pythonnative.bbclass
When inherited by a recipe, the pythonnative class supports using the native version of Python built
by the build system rather than using the version provided by the build host.

7.101. qemu.bbclass
The qemu class provides functionality for recipes that either need QEMU or test for the existence of
QEMU. Typically, this class is used to run programs for a target system on the build host using QEMU's
application emulation mode.

7.102. qmake*.bbclass
The qmake* classes support recipes that need to build software that uses Qt's qmake build system
and are comprised of the following:
• qmake_base: Provides base functionality for all versions of qmake.
• qmake2: Extends base functionality for qmake 2.x as used by Qt 4.x.
If you need to set any configuration variables or pass any options to qmake, you can add these to the
EXTRA_QMAKEVARS_PRE or EXTRA_QMAKEVARS_POST variables, depending on whether the arguments
need to be before or after the .pro file list on the command line, respectively.
By default, all .pro files are built. If you want to specify your own subset of .pro files to be built,
specify them in the QMAKE_PROFILES variable.

7.103. qt4*.bbclass
The qt4* classes support recipes that need to build software that uses the Qt development framework
version 4.x and consist of the following:
• qt4e: Supports building against Qt/Embedded, which uses the framebuffer for graphical output.
• qt4x11: Supports building against Qt/X11.
The classes inherit the qmake2 class.

7.104. relocatable.bbclass
The relocatable class enables relocation of binaries when they are installed into the sysroot.

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Classes

This class makes use of the chrpath class and is used by both the cross and native classes.

7.105. report-error.bbclass
The report-error class supports enabling the error reporting tool [http://www.yoctoproject.org/
docs/1.8/dev-manual/dev-manual.html#using-the-error-reporting-tool], which allows you to submit
build error information to a central database.
The class collects debug information for recipe, recipe version, task, machine, distro, build system,
target system, host distro, branch, commit, and log. From the information, report files using a JSON
format are created and stored in ${LOG_DIR}/error-report.

7.106. rm_work.bbclass
The rm_work class supports deletion of temporary workspace, which can ease your hard drive
demands during builds.
The OpenEmbedded build system can use a substantial amount of disk space during the build process.
A portion of this space is the work files under the ${TMPDIR}/work directory for each recipe. Once the
build system generates the packages for a recipe, the work files for that recipe are no longer needed.
However, by default, the build system preserves these files for inspection and possible debugging
purposes. If you would rather have these files deleted to save disk space as the build progresses,
you can enable rm_work by adding the following to your local.conf file, which is found in the Build
Directory [http://www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#build-directory].
INHERIT += "rm_work"
If you are modifying and building source code out of the work directory for a recipe, enabling rm_work
will potentially result in your changes to the source being lost. To exclude some recipes from having
their work directories deleted by rm_work, you can add the names of the recipe or recipes you are
working on to the RM_WORK_EXCLUDE variable, which can also be set in your local.conf file. Here
is an example:
RM_WORK_EXCLUDE += "busybox eglibc"

7.107. rootfs*.bbclass
The rootfs* classes support creating the root filesystem for an image and consist of the following
classes:
• The rootfs_deb class, which supports creation of root filesystems for images built using .deb
packages.
• The rootfs_rpm class, which supports creation of root filesystems for images built using .rpm
packages.
• The rootfs_ipk class, which supports creation of root filesystems for images built using .ipk
packages.
The root filesystem is created from packages using one of the rootfs*.bbclass files as determined
by the PACKAGE_CLASSES variable.
For information on how root filesystem images are created, see the "Image Generation" section.

7.108. sanity.bbclass
The sanity class checks to see if prerequisite software is present on the host system so that users
can be notified of potential problems that might affect their build. The class also performs basic user

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configuration checks from the local.conf configuration file to prevent common mistakes that cause
build failures. Distribution policy usually determines whether to include this class.

7.109. scons.bbclass
The scons class supports recipes that need to build software that uses the SCons build system. You
can use the EXTRA_OESCONS variable to specify additional configuration options you want to pass
SCons command line.

7.110. sdl.bbclass
The sdl class supports recipes that need to build software that uses the Simple DirectMedia Layer
(SDL) library.

7.111. setuptools.bbclass
The setuptools class supports Python version 2.x extensions that use build systems based on
setuptools. If your recipe uses these build systems, the recipe needs to inherit the setuptools class.

7.112. setuptools3.bbclass
The setuptools3 class supports Python version 3.x extensions that use build systems based on
setuptools3. If your recipe uses these build systems, the recipe needs to inherit the setuptools3
class.

7.113. sip.bbclass
The sip class supports recipes that build or package SIP-based Python bindings.

7.114. siteconfig.bbclass
The siteconfig class provides functionality for handling site configuration. The class is used by the
autotools class to accelerate the do_configure task.

7.115. siteinfo.bbclass
The siteinfo class provides information about the targets that might be needed by other classes
or recipes.
As an example, consider Autotools, which can require tests that must execute on the target hardware.
Since this is not possible in general when cross compiling, site information is used to provide cached
test results so these tests can be skipped over but still make the correct values available. The
meta/site directory contains test results sorted into different categories such as architecture,
endianness, and the libc used. Site information provides a list of files containing data relevant to
the current build in the CONFIG_SITE variable that Autotools automatically picks up.
The class also provides variables like SITEINFO_ENDIANNESS and SITEINFO_BITS that can be used
elsewhere in the metadata.
Because the base class includes the siteinfo class, it is always active.

7.116. spdx.bbclass
The spdx class integrates real-time license scanning, generation of SPDX standard output, and
verification of license information during the build.

Note
This class is currently at the prototype stage in the 1.6 release.

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7.117. sstate.bbclass
The sstate class provides support for Shared State (sstate). By default, the class is enabled through
the INHERIT_DISTRO variable's default value.
For more information on sstate, see the "Shared State Cache" section.

7.118. staging.bbclass
The staging class provides support for staging files into the sysroot during the do_populate_sysroot
task. The class is enabled by default because it is inherited by the base class.

7.119. syslinux.bbclass
The syslinux class provides syslinux-specific functions for building bootable images.
The class supports the following variables:
• INITRD: Indicates list of filesystem images to concatenate and use as an initial RAM disk (initrd).
This variable is optional.
• ROOTFS: Indicates a filesystem image to include as the root filesystem. This variable is optional.
• AUTO_SYSLINUXMENU: Enables creating an automatic menu when set to "1".
• LABELS: Lists targets for automatic configuration.
• APPEND: Lists append string overrides for each label.
• SYSLINUX_OPTS: Lists additional options to add to the syslinux file. Semicolon characters separate
multiple options.
• SYSLINUX_SPLASH: Lists a background for the VGA boot menu when you are using the boot menu.
• SYSLINUX_DEFAULT_CONSOLE: Set to "console=ttyX" to change kernel boot default console.
• SYSLINUX_SERIAL: Sets an alternate serial port. Or, turns off serial when the variable is set with
an empty string.
• SYSLINUX_SERIAL_TTY: Sets an alternate "console=tty..." kernel boot argument.

7.120. systemd.bbclass
The systemd class provides support for recipes that install systemd unit files.
The functionality for this class is disabled unless you have "systemd" in DISTRO_FEATURES.
Under this class, the recipe or Makefile (i.e. whatever the recipe is calling during the do_install
task) installs unit files into ${D}${systemd_unitdir}/system. If the unit files being installed go into
packages other than the main package, you need to set SYSTEMD_PACKAGES in your recipe to identify
the packages in which the files will be installed.
You should set SYSTEMD_SERVICE to the name of the service file. You should also use a package name
override to indicate the package to which the value applies. If the value applies to the recipe's main
package, use ${PN}. Here is an example from the connman recipe:
SYSTEMD_SERVICE_${PN} = "connman.service"
Services are set up to start on boot automatically unless you have set SYSTEMD_AUTO_ENABLE to
"disable".
For more information on systemd, see the "Selecting an Initialization Manager [http://
www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#selecting-an-initialization-manager]"
section in the Yocto Project Development Manual.

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7.121. terminal.bbclass
The terminal class provides support for starting a terminal session. The OE_TERMINAL variable
controls which terminal emulator is used for the session.
Other classes use the terminal class anywhere a separate terminal session needs to be started. For
example, the patch class assuming PATCHRESOLVE is set to "user", the cml1 class, and the devshell
class all use the terminal class.

7.122. testimage.bbclass
The testimage class supports running automated tests against images using QEMU and on actual
hardware. The class handles loading the tests and starting the image.
To use the class, you need to perform steps to set up the environment. The tests are commands that
run on the target system over ssh. they are written in Python and make use of the unittest module.
For information on how to enable, run, and create new tests, see the "Performing Automated
Runtime Testing [http://www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#performingautomated-runtime-testing]" section.

7.123. texinfo.bbclass
This class should be inherited by recipes whose upstream packages invoke the texinfo utilities at
build-time. Native and cross recipes are made to use the dummy scripts provided by texinfo-dummynative, for improved performance. Target architecture recipes use the genuine Texinfo utilities. By
default, they use the Texinfo utilities on the host system.

Note
If you want to use the Texinfo recipe shipped with the build system, you can remove "texinfonative" from ASSUME_PROVIDED and makeinfo from SANITY_REQUIRED_UTILITIES.

7.124. tinderclient.bbclass
The tinderclient class submits build results to an external Tinderbox instance.

Note
This class is currently unmaintained.

7.125. toaster.bbclass
The toaster class collects information about packages and images and sends them as events that
the BitBake user interface can receive. The class is enabled when the Toaster user interface is running.
This class is not intended to be used directly.

7.126. toolchain-scripts.bbclass
The toolchain-scripts class provides the scripts used for setting up the environment for installed
SDKs.

7.127. typecheck.bbclass
The typecheck class provides support for validating the values of variables set at the configuration
level against their defined types. The OpenEmbedded build system allows you to define the type of
a variable using the "type" varflag. Here is an example:
IMAGE_FEATURES[type] = "list"

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7.128. uboot-config.bbclass
The uboot-config class provides support for U-Boot configuration for a machine. Specify the machine
in your recipe as follows:
UBOOT_CONFIG ??= 
UBOOT_CONFIG[foo] = "config,images"
You can also specify the machine using this method:
UBOOT_MACHINE = "config"
See the UBOOT_CONFIG and UBOOT_MACHINE variables for additional information.

7.129. uninative.bbclass
Provides a means of reusing native/cross over multiple distros.

Note
Currently, the method used by the uninative class is experimental.
For more information, see the commit message here [http://cgit.openembedded.org/openembeddedcore/commit/?id=e66c96ae9c7ba21ebd04a4807390f0031238a85a].

7.130. update-alternatives.bbclass
The update-alternatives class helps the alternatives system when multiple sources provide the
same command. This situation occurs when several programs that have the same or similar function
are installed with the same name. For example, the ar command is available from the busybox,
binutils and elfutils packages. The update-alternatives class handles renaming the binaries
so that multiple packages can be installed without conflicts. The ar command still works regardless
of which packages are installed or subsequently removed. The class renames the conflicting binary
in each package and symlinks the highest priority binary during installation or removal of packages.
To use this class, you need to define a number of variables:
• ALTERNATIVE
• ALTERNATIVE_LINK_NAME
• ALTERNATIVE_TARGET
• ALTERNATIVE_PRIORITY
These variables list alternative commands needed by a package, provide pathnames for links,
default links for targets, and so forth. For details on how to use this class, see the comments in
the update-alternatives.bbclass [http://git.yoctoproject.org/cgit/cgit.cgi/poky/tree/meta/classes/
update-alternatives.bbclass].

Note
You can use the update-alternatives command directly in your recipes. However, this class
simplifies things in most cases.

7.131. update-rc.d.bbclass
The update-rc.d class uses update-rc.d to safely install an initialization script on behalf of the
package. The OpenEmbedded build system takes care of details such as making sure the script is
stopped before a package is removed and started when the package is installed.
Three
variables
control
this
class:
INITSCRIPT_PACKAGES,
INITSCRIPT_PARAMS. See the variable links for details.

104

INITSCRIPT_NAME

and

Classes

7.132. useradd.bbclass
The useradd class supports the addition of users or groups for usage by the package on the target.
For example, if you have packages that contain system services that should be run under their
own user or group, you can use this class to enable creation of the user or group. The metaskeleton/recipes-skeleton/useradd/useradd-example.bb recipe in the Source Directory [http://
www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#source-directory] provides a simple
example that shows how to add three users and groups to two packages. See the useraddexample.bb recipe for more information on how to use this class.
The useradd class supports the USERADD_PACKAGES, USERADD_PARAM, GROUPADD_PARAM, and
GROUPMEMS_PARAM variables.

7.133. useradd-staticids.bbclass
The useradd-staticids class supports the addition of users or groups that have static user
identification (uid) and group identification (gid) values.
The default behavior of the OpenEmbedded build system for assigning uid and gid values when
packages add users and groups during package install time is to add them dynamically. This works
fine for programs that do not care what the values of the resulting users and groups become. In
these cases, the order of the installation determines the final uid and gid values. However, if nondeterministic uid and gid values are a problem, you can override the default, dynamic application of
these values by setting static values. When you set static values, the OpenEmbedded build system
looks in BBPATH for files/passwd and files/group files for the values.
To use static uid and gid values, you need to set some variables. See the USERADDEXTENSION,
USERADD_UID_TABLES, USERADD_GID_TABLES, and USERADD_ERROR_DYNAMIC variables. You can also
see the useradd class for additional information.

Notes
You do not use this class directly. You either enable or disable the class by setting the
USERADDEXTENSION variable. If you enable or disable the class in a configured system, TMPDIR
might contain incorrect uid and gid values. Deleting the TMPDIR directory will correct this
condition.

7.134. utility-tasks.bbclass
The utility-tasks class provides support for various "utility" type tasks that are applicable to all
recipes, such as do_clean and do_listtasks.
This class is enabled by default because it is inherited by the base class.

7.135. utils.bbclass
The utils class provides some useful Python functions that are typically used in inline Python
expressions (e.g. ${@...}). One example use is for bb.utils.contains().
This class is enabled by default because it is inherited by the base class.

7.136. vala.bbclass
The vala class supports recipes that need to build software written using the Vala programming
language.

7.137. waf.bbclass
The waf class supports recipes that need to build software that uses the Waf build system. You can
use the EXTRA_OECONF variable to specify additional configuration options to be passed on the Waf
command line.

105

Chapter 8. Tasks
Tasks are units of execution for BitBake. Recipes (.bb files) use tasks to complete configuring,
compiling, and packaging software. This chapter provides a reference of the tasks defined in the
OpenEmbedded build system.

8.1. Normal Recipe Build Tasks
The following sections describe normal tasks associated with building a recipe.

8.1.1. do_build
The default task for all recipes. This task depends on all other normal tasks required to build a recipe.

8.1.2. do_compile
Compiles the source in the compilation directory, which is pointed to by the B variable.

8.1.3. do_compile_ptest_base
Compiles the runtime test suite included in the software being built.

8.1.4. do_configure
Configures the source by enabling and disabling any build-time and configuration options for the
software being built.

8.1.5. do_configure_ptest_base
Configures the runtime test suite included in the software being built.

8.1.6. do_deploy
Writes output files that are to be deployed to the deploy directory, which is defined by the DEPLOYDIR
variable.
The do_deploy task is a shared state (sstate) task, which means that the task can be accelerated
through sstate use. Realize also that if the task is re-executed, any previous output is removed (i.e.
"cleaned").

8.1.7. do_fetch
Fetches the source code. This task uses the SRC_URI variable and the argument's prefix to determine
the correct fetcher module.

8.1.8. do_install
Copies files from the compilation directory, which is defined by the B variable, to a holding area
defined by the D variable.

8.1.9. do_install_ptest_base
Copies the runtime test suite files from the compilation directory to a holding area.

8.1.10. do_package
Analyzes the content of the holding area and splits it into subsets based on available packages and
files.

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Tasks

8.1.11. do_package_qa
Runs QA checks on packaged files. For more information on these checks, see the insane class.

8.1.12. do_package_write_deb
Creates the actual DEB packages and places them in the Package Feeds area.

8.1.13. do_package_write_ipk
Creates the actual IPK packages and places them in the Package Feeds area.

8.1.14. do_package_write_rpm
Creates the actual RPM packages and places them in the Package Feeds area.

8.1.15. do_package_write_tar
Creates tar archives for packages and places them in the Package Feeds area.

8.1.16. do_packagedata
Creates package metadata used by the build system to generate the final packages.

8.1.17. do_patch
Locates patch files and applies them to the source code. See the "Patching" section for more
information.

8.1.18. do_populate_lic
Writes license information for the recipe that is collected later when the image is constructed.

8.1.19. do_populate_sdk
Creates the file and directory structure for an installable SDK. See the "SDK Generation" section for
more information.

8.1.20. do_populate_sysroot
Copies a subset of files installed by the do_install task into the sysroot in order to make them
available to other recipes.
The do_populate_sysroot task is a shared state (sstate) task, which means that the task can be
accelerated through sstate use. Realize also that if the task is re-executed, any previous output is
removed (i.e. "cleaned").

8.1.21. do_rm_work
Removes work files after the OpenEmbedded build system has finished with them. You can learn more
by looking at the "rm_work.bbclass" section.

8.1.22. do_rm_work_all
Top-level task for removing work files after the build system has finished with them.

8.1.23. do_unpack
Unpacks the source code into a working directory pointed to by ${WORKDIR}. The S variable also plays
a role in where unpacked source files ultimately reside. For more information on how source files are
unpacked, see the "Source Fetching" section and the WORKDIR and S variable descriptions.

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Tasks

8.2. Manually Called Tasks
These tasks are typically manually triggered (e.g. by using the bitbake -c command-line option):

8.2.1. do_checkuri
Validates the SRC_URI value.

8.2.2. do_checkuriall
Validates the SRC_URI value for all recipes required to build a target.

8.2.3. do_clean
Removes all output files for a target from the do_unpack task forward (i.e. do_unpack, do_configure,
do_compile, do_install, and do_package).
You can run this task using BitBake as follows:
$ bitbake -c clean recipe
Running this task does not remove the sstate) cache files. Consequently, if no changes have been
made and the recipe is rebuilt after cleaning, output files are simply restored from the sstate cache.
If you want to remove the sstate cache files for the recipe, you need to use the do_cleansstate task
instead (i.e. bitbake -c cleansstate recipe).

8.2.4. do_cleanall
Removes all output files, shared state (sstate) cache, and downloaded source files for a target (i.e.
the contents of DL_DIR). Essentially, the do_cleanall task is identical to the do_cleansstate task
with the added removal of downloaded source files.
You can run this task using BitBake as follows:
$ bitbake -c cleanall recipe
Typically, you would not normally use the cleanall task. Do so only if you want to start fresh with
the do_fetch task.

8.2.5. do_cleansstate
Removes all output files and shared state (sstate) cache for a target. Essentially, the do_cleansstate
task is identical to the do_clean task with the added removal of shared state (sstate) cache.
You can run this task using BitBake as follows:
$ bitbake -c cleansstate recipe
When you run the do_cleansstate task, the OpenEmbedded build system no longer uses any sstate.
Consequently, building the recipe from scratch is guaranteed.

Note
The do_cleansstate task cannot remove sstate from a remote sstate mirror. If you need to
build a target from scratch using remote mirrors, use the "-f" option as follows:
$ bitbake -f -c do_cleansstate target

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Tasks

8.2.6. do_devshell
Starts a shell whose environment is set up for development, debugging, or both. See the "Using
a Development Shell [http://www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#platdevappdev-devshell]" section in the Yocto Project Development Manual for more information about using
devshell.

8.2.7. do_fetchall
Fetches all remote sources required to build a target.

8.2.8. do_listtasks
Lists all defined tasks for a target.

8.2.9. do_package_index
Creates or updates the index in the Package Feeds area.

Note
This task is not triggered with the bitbake -c command-line option as are the other tasks in
this section. Because this task is specifically for the package-index recipe, you run it using
bitbake package-index.

8.3. Image-Related Tasks
The following tasks are applicable to image recipes.

8.3.1. do_bootimg
Creates a bootable live image. See the IMAGE_FSTYPES variable for additional information on live
image types.

8.3.2. do_bundle_initramfs
Combines an initial RAM disk (initramfs) image and kernel together to form a single image. The
CONFIG_INITRAMFS_SOURCE variable has some more information about these types of images.

8.3.3. do_rootfs
Creates the root filesystem (file and directory structure) for an image. See the "Image Generation"
section for more information on how the root filesystem is created.

8.3.4. do_testimage
Boots an image and performs runtime tests within the image. For information on automatically testing
images, see the "Performing Automated Runtime Testing [http://www.yoctoproject.org/docs/1.8/
dev-manual/dev-manual.html#performing-automated-runtime-testing]" section in the Yocto Project
Development Manual.

8.3.5. do_testimage_auto
Boots an image and performs runtime tests within the image immediately after it has been built. This
task is enabled when you set TEST_IMAGE equal to "1".
For information on automatically testing images, see the "Performing Automated
Runtime Testing [http://www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#performingautomated-runtime-testing]" section in the Yocto Project Development Manual.

109

Tasks

8.3.6. do_vmdkimg
Creates a .vmdk image for use with VMware [http://www.vmware.com/] and compatible virtual
machine hosts.

8.4. Kernel-Related Tasks
The following tasks are applicable to kernel recipes. Some of these tasks (e.g. the do_menuconfig
task) are also applicable to recipes that use Linux kernel style configuration such as the BusyBox
recipe.

8.4.1. do_compile_kernelmodules
Compiles loadable modules for the Linux kernel.

8.4.2. do_diffconfig
Compares the old and new config files after running the do_menuconfig task for the kernel.

8.4.3. do_kernel_checkout
Checks out source/meta branches for a linux-yocto style kernel.

8.4.4. do_kernel_configcheck
Validates the kernel configuration for a linux-yocto style kernel.

8.4.5. do_kernel_configme
Assembles the kernel configuration for a linux-yocto style kernel.

8.4.6. do_kernel_link_vmlinux
Creates a symbolic link in arch/$arch/boot for vmlinux kernel images.

8.4.7. do_menuconfig
Runs make menuconfig for the kernel. For information on menuconfig, see the "Using menuconfig
[http://www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#using-menuconfig]" section in
the Yocto Project Development Manual.

8.4.8. do_savedefconfig
Creates a minimal Linux kernel configuration file.

8.4.9. do_sizecheck
Checks the size of the kernel image against KERNEL_IMAGE_MAXSIZE when set.

8.4.10. do_strip
Strips unneeded sections out of the Linux kernel image.

8.4.11. do_uboot_mkimage
Creates a uImage file from the kernel for the U-Boot bootloader.

8.4.12. do_validate_branches
Ensures that the source, metadata (or both) branches are on the locations specified by their SRCREV
values for a linux-yocto style kernel.

110

Tasks

8.5. Miscellaneous Tasks
The following sections describe miscellaneous tasks.

8.5.1. do_generate_qt_config_file
Writes a qt.conf configuration file used for building a Qt-based application.

8.5.2. do_spdx
A build stage that takes the source code and scans it on a remote FOSSOLOGY server in order to
produce an SPDX document. This task applies only to the spdx class.

111

Chapter 9. QA Error and Warning
Messages
9.1. Introduction
When building a recipe, the OpenEmbedded build system performs various QA checks on the output
to ensure that common issues are detected and reported. Sometimes when you create a new recipe
to build new software, it will build with no problems. When this is not the case, or when you have QA
issues building any software, it could take a little time to resolve them.
While it is tempting to ignore a QA message or even to disable QA checks, it is best to try and resolve
any reported QA issues. This chapter provides a list of the QA messages and brief explanations of the
issues you could encounter so that you can properly resolve problems.
The next section provides a list of all QA error and warning messages based on a default configuration.
Each entry provides the message or error form along with an explanation.

Notes
• At the end of each message, the name of the associated QA test (as listed in the
"insane.bbclass" section) appears within square brackets.
• As mentioned, this list of error and warning messages is for QA checks only. The list does
not cover all possible build errors or warnings you could encounter.
• Because some QA checks are disabled by default, this list does not include all possible QA
check errors and warnings.

9.2. Errors and Warnings
• :  is using libexec please relocate to  [libexec]
The specified package contains files in /usr/libexec. By default, libexecdir is set to "${libdir}/
${BPN}" rather than to "/usr/libexec". Thus, installing to /usr/libexec is likely not desirable.

• package  contains bad RPATH  in file  [rpaths]
The specified binary produced by the recipe contains dynamic library load paths (rpaths) that
contain build system paths such as TMPDIR, which are incorrect for the target and could potentially
be a security issue. Check for bad -rpath options being passed to the linker in your do_compile
log. Depending on the build system used by the software being built, there might be a configure
option to disable rpath usage completely within the build of the software.

• :  contains probably-redundant RPATH  [useless-rpaths]
The specified binary produced by the recipe contains dynamic library load paths (rpaths) that on a
standard system are searched by default by the linker (e.g. /lib and /usr/lib). While these paths
will not cause any breakage, they do waste space and are unnecessary. Depending on the build
system used by the software being built, there might be a configure option to disable rpath usage
completely within the build of the software.

•  requires , but no providers in its RDEPENDS [file-rdeps]
A file-level dependency has been identified from the specified package on the specified files, but
there is no explicit corresponding entry in RDEPENDS. If particular files are required at runtime then
RDEPENDS should be declared in the recipe to ensure the packages providing them are built.

112

QA Error and Warning Messages

•  rdepends on , but it isn't a build dependency? [builddeps]
A runtime dependency exists between the two specified packages, but there is nothing explicit
within the recipe to enable the OpenEmbedded build system to ensure that dependency is satisfied.
This condition is usually triggered by an RDEPENDS value being added at the packaging stage rather
than up front, which is usually automatic based on the contents of the package. In most cases, you
should change the recipe to add an explicit RDEPENDS for the dependency.

• non -dev/-dbg/-nativesdk
'' [dev-so]

package

contains

symlink

.so:



path

Symlink .so files are for development only, and should therefore go into the -dev package. This
situation might occur if you add *.so* rather than *.so.* to a non-dev package. Change FILES
(and possibly PACKAGES) such that the specified .so file goes into an appropriate -dev package.

• non
-staticdev
package
'' [staticdev]

contains

static

.a

library:



path

Static .a library files should go into a -staticdev package. Change FILES (and possibly PACKAGES)
such that the specified .a file goes into an appropriate -staticdev package.

• : found library in wrong location [libdir]
The specified file may have been installed into an incorrect (possibly hardcoded) installation path.
For example, this test will catch recipes that install /lib/bar.so when ${base_libdir} is "lib32".
Another example is when recipes install /usr/lib64/foo.so when ${libdir} is "/usr/lib". False
positives occasionally exist. For these cases add "libdir" to INSANE_SKIP for the package.

• non debug package contains .debug directory:  path  [debug-files]
The specified package contains a .debug directory, which should not appear in anything but the dbg package. This situation might occur if you add a path which contains a .debug directory and
do not explicitly add the .debug directory to the -dbg package. If this is the case, add the .debug
directory explicitly to FILES_${PN}-dbg. See FILES for additional information on FILES.

• Architecture did not match ( to ) on  [arch]
By default, the OpenEmbedded build system checks the Executable and Linkable Format (ELF) type,
bit size, and endianness of any binaries to ensure they match the target architecture. This test
fails if any binaries do not match the type since there would be an incompatibility. The test could
indicate that the wrong compiler or compiler options have been used. Sometimes software, like
bootloaders, might need to bypass this check. If the file you receive the error for is firmware that is
not intended to be executed within the target operating system or is intended to run on a separate
processor within the device, you can add "arch" to INSANE_SKIP for the package. Another option is
to check the do_compile log and verify that the compiler options being used are correct.

• Bit size did not match ( to )  on  [arch]
By default, the OpenEmbedded build system checks the Executable and Linkable Format (ELF) type,
bit size, and endianness of any binaries to ensure they match the target architecture. This test
fails if any binaries do not match the type since there would be an incompatibility. The test could
indicate that the wrong compiler or compiler options have been used. Sometimes software, like
bootloaders, might need to bypass this check. If the file you receive the error for is firmware that is
not intended to be executed within the target operating system or is intended to run on a separate
113

QA Error and Warning Messages

processor within the device, you can add "arch" to INSANE_SKIP for the package. Another option is
to check the do_compile log and verify that the compiler options being used are correct.

• Endianness did not match ( to ) on 
[arch]
By default, the OpenEmbedded build system checks the Executable and Linkable Format (ELF) type,
bit size, and endianness of any binaries to ensure they match the target architecture. This test
fails if any binaries do not match the type since there would be an incompatibility. The test could
indicate that the wrong compiler or compiler options have been used. Sometimes software, like
bootloaders, might need to bypass this check. If the file you receive the error for is firmware that is
not intended to be executed within the target operating system or is intended to run on a separate
processor within the device, you can add "arch" to INSANE_SKIP for the package. Another option is
to check the do_compile log and verify that the compiler options being used are correct.

• ELF binary '' has relocations in .text [textrel]
The specified ELF binary contains relocations in its .text sections. This situation can result in a
performance impact at runtime.

• No GNU_HASH in the elf binary: '' [ldflags]
This indicates that binaries produced when building the recipe have not been linked with the
LDFLAGS options provided by the build system. Check to be sure that the LDFLAGS variable is being
passed to the linker command. A common workaround for this situation is to pass in LDFLAGS using
TARGET_CC_ARCH within the recipe as follows:
TARGET_CC_ARCH += "${LDFLAGS}"

• Package  contains Xorg driver () but no xorg-abi- dependencies
[xorg-driver-abi]
The specified package contains an Xorg driver, but does not have a corresponding ABI package
dependency. The xserver-xorg recipe provides driver ABI names. All drivers should depend on the
ABI versions that they have been built against. Driver recipes that include xorg-driver-input.inc
or xorg-driver-video.inc will automatically get these versions. Consequently, you should only
need to explicitly add dependencies to binary driver recipes.

• The /usr/share/info/dir file is not meant to be shipped in a particular package.
[infodir]
The /usr/share/info/dir should not be packaged. Add the following line to your do_install task
or to your do_install_append within the recipe as follows:
rm ${D}${infodir}/dir

• Symlink  in  points to TMPDIR [symlink-to-sysroot]
The specified symlink points into TMPDIR on the host. Such symlinks will work on the host. However,
they are clearly invalid when running on the target. You should either correct the symlink to use
a relative path or remove the symlink.

114

QA Error and Warning Messages

•  failed sanity test (workdir) in path  [la]
The specified .la file contains TMPDIR paths. Any .la file containing these paths is incorrect since
libtool adds the correct sysroot prefix when using the files automatically itself.

•  failed sanity test (tmpdir) in path  [pkgconfig]
The specified .pc file contains TMPDIR/WORKDIR paths. Any .pc file containing these paths is
incorrect since pkg-config itself adds the correct sysroot prefix when the files are accessed.

•  rdepends on  [debug-deps]
A dependency exists between the specified non-dbg package (i.e. a package whose name does not
end in -dbg) and a package that is a dbg package. The dbg packages contain debug symbols and
are brought in using several different methods:
• Using the dbg-pkgs IMAGE_FEATURES value.
• Using IMAGE_INSTALL.
• As a dependency of another dbg package that was brought in using one of the above methods.
The dependency might have been automatically added because the dbg package erroneously
contains files that it should not contain (e.g. a non-symlink .so file) or it might have been added
manually (e.g. by adding to RDEPENDS).

•  rdepends on  [dev-deps]
A dependency exists between the specified non-dev package (a package whose name does not end
in -dev) and a package that is a dev package. The dev packages contain development headers and
are usually brought in using several different methods:
• Using the dev-pkgs IMAGE_FEATURES value.
• Using IMAGE_INSTALL.
• As a dependency of another dev package that was brought in using one of the above methods.
The dependency might have been automatically added (because the dev package erroneously
contains files that it should not have (e.g. a non-symlink .so file) or it might have been added
manually (e.g. by adding to RDEPENDS).

• _ is invalid:  () only comparisons <, =, >,
<=, and >= are allowed [dep-cmp]
If you are adding a versioned dependency relationship to one of the dependency variables
(RDEPENDS, RRECOMMENDS, RSUGGESTS, RPROVIDES, RREPLACES, or RCONFLICTS), you must only use
the named comparison operators. Change the versioned dependency values you are adding to
match those listed in the message.

• : The compile log indicates that host include and/or library paths were
used. Please check the log '' for more information. [compile-host-path]
The log for the do_compile task indicates that paths on the host were searched for files, which is not
appropriate when cross-compiling. Look for "is unsafe for cross-compilation" or "CROSS COMPILE
Badness" in the specified log file.

• : The install log indicates that host include and/or library paths were
used. Please check the log '' for more information. [install-host-path]

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QA Error and Warning Messages

The log for the do_install task indicates that paths on the host were searched for files, which is not
appropriate when cross-compiling. Look for "is unsafe for cross-compilation" or "CROSS COMPILE
Badness" in the specified log file.

• This autoconf log indicates errors, it looked at host include and/or library paths
while determining system capabilities. Rerun configure task after fixing this. The
path was ''
The log for the do_configure task indicates that paths on the host were searched for files, which
is not appropriate when cross-compiling. Look for "is unsafe for cross-compilation" or "CROSS
COMPILE Badness" in the specified log file.

•  doesn't match the [a-z0-9.+-]+ regex [pkgname]
The convention within the OpenEmbedded build system (sometimes enforced by the package
manager itself) is to require that package names are all lower case and to allow a restricted set
of characters. If your recipe name does not match this, or you add packages to PACKAGES that do
not conform to the convention, then you will receive this error. Rename your recipe. Or, if you have
added a non-conforming package name to PACKAGES, change the package name appropriately.

• : configure was passed unrecognized options:  [unknown-configureoption]
The configure script is reporting that the specified options are unrecognized. This situation could
be because the options were previously valid but have been removed from the configure script.
Or, there was a mistake when the options were added and there is another option that should
be used instead. If you are unsure, consult the upstream build documentation, the ./configure
##help output, and the upstream change log or release notes. Once you have worked out what
the appropriate change is, you can update EXTRA_OECONF or the individual PACKAGECONFIG option
values accordingly.

• Recipe  has PN of "" which is in OVERRIDES, this can result
in unexpected behavior. [pn-overrides]
The specified recipe has a name (PN) value that appears in OVERRIDES. If a recipe is named such that
its PN value matches something already in OVERRIDES (e.g. PN happens to be the same as MACHINE
or DISTRO), it can have unexpected consequences. For example, assignments such as FILES_${PN}
= "xyz" effectively turn into FILES = "xyz". Rename your recipe (or if PN is being set explicitly,
change the PN value) so that the conflict does not occur. See FILES for additional information.

• : Variable  is set as not being package specific, please fix
this. [pkgvarcheck]
Certain variables (RDEPENDS, RRECOMMENDS, RSUGGESTS, RCONFLICTS, RPROVIDES, RREPLACES,
FILES, pkg_preinst, pkg_postinst, pkg_prerm, pkg_postrm, and ALLOW_EMPTY) should always
be set specific to a package (i.e. they should be set with a package name override such as
RDEPENDS_${PN} = "value" rather than RDEPENDS = "value"). If you receive this error, correct
any assignments to these variables within your recipe.

• File '' from  was already stripped, this will prevent future
debugging! [already-stripped]
Produced binaries have already been stripped prior to the build system extracting debug symbols. It
is common for upstream software projects to default to stripping debug symbols for output binaries.
In order for debugging to work on the target using -dbg packages, this stripping must be disabled.

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QA Error and Warning Messages

Depending on the build system used by the software being built, disabling this stripping could be as
easy as specifying an additional configure option. If not, disabling stripping might involve patching
the build scripts. In the latter case, look for references to "strip" or "STRIP", or the "-s" or "-S"
command-line options being specified on the linker command line (possibly through the compiler
command line if preceded with "-Wl,").

Note
Disabling stripping here does not mean that the final packaged binaries will be unstripped.
Once the OpenEmbedded build system splits out debug symbols to the -dbg package, it
will then strip the symbols from the binaries.

•  is listed in PACKAGES multiple times, this leads to packaging errors.
[packages-list]
Package names must appear only once in the PACKAGES variable. You might receive this error if you
are attempting to add a package to PACKAGES that is already in the variable's value.

• FILES variable for package  contains '//' which is invalid. Attempting
to fix this but you should correct the metadata. [files-invalid]
The string "//" is invalid in a Unix path. Correct all occurrences where this string appears in a FILES
variable so that there is only a single "/".

• :
shipped]

Files/directories

were

installed

but

not

shipped

[installed-vs-

Files have been installed within the do_install task but have not been included in any package by
way of the FILES variable. Files that do not appear in any package cannot be present in an image
later on in the build process. You need to do one of the following:
• Add the files to FILES for the package you want them to appear in (e.g. FILES_${PN} for the
main package).
• Delete the files at the end of the do_install task if the files are not needed in any package.

• - was registered as shlib provider for ,
changing it to - because it was built later
This message means that both  and  provide the specified shared
library. You can expect this message when a recipe has been renamed. However, if that is not the
case, the message might indicate that a private version of a library is being erroneously picked up
as the provider for a common library. If that is the case, you should add the library's .so file name
to PRIVATE_LIBS in the recipe that provides the private version of the library.

9.3. Configuring and Disabling QA Checks
You can configure the QA checks globally so that specific check failures either raise a warning or an
error message, using the WARN_QA and ERROR_QA variables, respectively. You can also disable checks
within a particular recipe using INSANE_SKIP. For information on how to work with the QA checks,
see the "insane.bbclass" section.

Tip
Please keep in mind that the QA checks exist in order to detect real or potential problems in
the packaged output. So exercise caution when disabling these checks.

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Chapter 10. Images
The OpenEmbedded build system provides several example images to satisfy different needs. When
you issue the bitbake command you provide a “top-level” recipe that essentially begins the build
for the type of image you want.

Note
Building an image without GNU General Public License Version 3 (GPLv3), GNU Lesser General
Public License Version 3 (LGPLv3), and the GNU Affero General Public License Version 3
(AGPL-3.0) components is only supported for minimal and base images. Furthermore, if you
are going to build an image using non-GPLv3 and similarly licensed components, you must
make the following changes in the local.conf file before using the BitBake command to
build the minimal or base image:
1. Comment out the EXTRA_IMAGE_FEATURES line
2. Set INCOMPATIBLE_LICENSE = "GPL-3.0 LGPL-3.0 AGPL-3.0"
From within the poky Git repository, you can use the following command to display the list
of directories within the Source Directory [http://www.yoctoproject.org/docs/1.8/dev-manual/devmanual.html#source-directory] that containe image recipe files:
$ ls meta*/recipes*/images/*.bb
Following is a list of supported recipes:
• build-appliance-image: An example virtual machine that contains all the pieces required to
run builds using the build system as well as the build system itself. You can boot and run the
image using either the VMware Player [http://www.vmware.com/products/player/overview.html]
or VMware Workstation [http://www.vmware.com/products/workstation/overview.html]. For more
information on this image, see the Build Appliance [http://www.yoctoproject.org/documentation/
build-appliance] page on the Yocto Project website.
• core-image-base: A console-only image that fully supports the target device hardware.
• core-image-clutter: An image with support for the Open GL-based toolkit Clutter, which enables
development of rich and animated graphical user interfaces.
• core-image-directfb: An image that uses directfb instead of X11.
• core-image-full-cmdline: A console-only image with more full-featured Linux system
functionality installed.
• core-image-lsb: An image that conforms to the Linux Standard Base (LSB) specification. This
image requires a distribution configuration that enables LSB compliance (e.g. poky-lsb). If you
build core-image-lsb without that configuration, the image will not be LSB-compliant.
• core-image-lsb-dev: A core-image-lsb image that is suitable for development work using the
host. The image includes headers and libraries you can use in a host development environment.
This image requires a distribution configuration that enables LSB compliance (e.g. poky-lsb). If
you build core-image-lsb-dev without that configuration, the image will not be LSB-compliant.
• core-image-lsb-sdk: A core-image-lsb that includes everything in meta-toolchain but also
includes development headers and libraries to form a complete standalone SDK. This image
requires a distribution configuration that enables LSB compliance (e.g. poky-lsb). If you build
core-image-lsb-sdk without that configuration, the image will not be LSB-compliant. This image
is suitable for development using the target.
• core-image-minimal: A small image just capable of allowing a device to boot.
• core-image-minimal-dev: A core-image-minimal image suitable for development work using the
host. The image includes headers and libraries you can use in a host development environment.

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Images

• core-image-minimal-initramfs: A core-image-minimal image that has the Minimal RAM-based
Initial Root Filesystem (initramfs) as part of the kernel, which allows the system to find the first
“init” program more efficiently. See the PACKAGE_INSTALL variable for additional information helpful
when working with initramfs images.
• core-image-minimal-mtdutils: A core-image-minimal image that has support for the Minimal
MTD Utilities, which let the user interact with the MTD subsystem in the kernel to perform operations
on flash devices.
• core-image-rt: A core-image-minimal image plus a real-time test suite and tools appropriate for
real-time use.
• core-image-rt-sdk: A core-image-rt image that includes everything in meta-toolchain. The
image also includes development headers and libraries to form a complete stand-alone SDK and
is suitable for development using the target.
• core-image-sato: An image with Sato support, a mobile environment and visual style that works
well with mobile devices. The image supports X11 with a Sato theme and applications such as a
terminal, editor, file manager, media player, and so forth.
• core-image-sato-dev: A core-image-sato image suitable for development using the host. The
image includes libraries needed to build applications on the device itself, testing and profiling tools,
and debug symbols. This image was formerly core-image-sdk.
• core-image-sato-sdk: A core-image-sato image that includes everything in meta-toolchain. The
image also includes development headers and libraries to form a complete standalone SDK and is
suitable for development using the target.
• core-image-testmaster: A "master" image designed to be used for automated runtime testing.
Provides a "known good" image that is deployed to a separate partition so that you can boot into
it and use it to deploy a second image to be tested. You can find more information about runtime
testing in the "Performing Automated Runtime Testing [http://www.yoctoproject.org/docs/1.8/devmanual/dev-manual.html#performing-automated-runtime-testing]" section in the Yocto Project
Development Manual.
• core-image-testmaster-initramfs: A RAM-based Initial Root Filesystem (initramfs) image
tailored for use with the core-image-testmaster image.
• core-image-weston: A very basic Wayland image with a terminal. This image provides the Wayland
protocol libraries and the reference Weston compositor. For more information, see the "Wayland"
section.
• core-image-x11: A very basic X11 image with a terminal.
• qt4e-demo-image: An image that launches into the demo application for the embedded (not based
on X11) version of Qt.

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Chapter 11. Features
This chapter provides a reference of shipped machine and distro features you can include as part of
your image, a reference on image features you can select, and a reference on feature backfilling.
Features provide a mechanism for working out which packages should be included in the generated
images. Distributions can select which features they want to support through the DISTRO_FEATURES
variable, which is set or appended to in a distribution's configuration file such as poky.conf, pokytiny.conf, poky-lsb.conf and so forth. Machine features are set in the MACHINE_FEATURES variable,
which is set in the machine configuration file and specifies the hardware features for a given machine.
These two variables combine to work out which kernel modules, utilities, and other packages to
include. A given distribution can support a selected subset of features so some machine features
might not be included if the distribution itself does not support them.
One method you can use to determine which recipes are checking to see if a particular feature is
contained or not is to grep through the Metadata [http://www.yoctoproject.org/docs/1.8/dev-manual/
dev-manual.html#metadata] for the feature. Here is an example that discovers the recipes whose
build is potentially changed based on a given feature:
$ cd poky
$ git grep 'contains.*MACHINE_FEATURES.*feature'

11.1. Machine Features
The items below are features you can use with MACHINE_FEATURES. Features do not have a one-toone correspondence to packages, and they can go beyond simply controlling the installation of a
package or packages. Sometimes a feature can influence how certain recipes are built. For example,
a feature might determine whether a particular configure option is specified within the do_configure
task for a particular recipe.
This feature list only represents features as shipped with the Yocto Project metadata:
• acpi: Hardware has ACPI (x86/x86_64 only)
• alsa: Hardware has ALSA audio drivers
• apm: Hardware uses APM (or APM emulation)
• bluetooth: Hardware has integrated BT
• efi: Support for booting through EFI
• ext2: Hardware HDD or Microdrive
• irda: Hardware has IrDA support
• keyboard: Hardware has a keyboard
• pcbios: Support for booting through BIOS
• pci: Hardware has a PCI bus
• pcmcia: Hardware has PCMCIA or CompactFlash sockets
• phone: Mobile phone (voice) support
• qvga: Machine has a QVGA (320x240) display
• rtc: Machine has a Real-Time Clock
• screen: Hardware has a screen
• serial: Hardware has serial support (usually RS232)

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Features

• touchscreen: Hardware has a touchscreen
• usbgadget: Hardware is USB gadget device capable
• usbhost: Hardware is USB Host capable
• vfat: FAT file system support
• wifi: Hardware has integrated WiFi

11.2. Distro Features
The items below are features you can use with DISTRO_FEATURES to enable features across your
distribution. Features do not have a one-to-one correspondence to packages, and they can go
beyond simply controlling the installation of a package or packages. In most cases, the presence or
absence of a feature translates to the appropriate option supplied to the configure script during the
do_configure task for the recipes that optionally support the feature.
Some distro features are also machine features. These select features make sense to be controlled
both at the machine and distribution configuration level. See the COMBINED_FEATURES [http://
www.yoctoproject.org/docs/1.8/ref-manual/ref-manual.html#var-COMBINED_FEATURES] variable for
more information.
This list only represents features as shipped with the Yocto Project metadata:
• alsa: Include ALSA support (OSS compatibility kernel modules installed if available).
• bluetooth: Include bluetooth support (integrated BT only).
• cramfs: Include CramFS support.
• directfb: Include DirectFB support.
• ext2: Include tools for supporting for devices with internal HDD/Microdrive for storing files (instead
of Flash only devices).
• ipsec: Include IPSec support.
• ipv6: Include IPv6 support.
• irda: Include IrDA support.
• keyboard: Include keyboard support (e.g. keymaps will be loaded during boot).
• nfs: Include NFS client support (for mounting NFS exports on device).
• opengl: Include the Open Graphics Library, which is a cross-language, multi-platform application
programming interface used for rendering two and three-dimensional graphics.
• pci: Include PCI bus support.
• pcmcia: Include PCMCIA/CompactFlash support.
• ppp: Include PPP dialup support.
• smbfs: Include SMB networks client support (for mounting Samba/Microsoft Windows shares on
device).
• systemd: Include support for this init manager, which is a full replacement of for init with parallel
starting of services, reduced shell overhead, and other features. This init manager is used by
many distributions.
• usbgadget: Include USB Gadget Device support (for USB networking/serial/storage).
• usbhost: Include USB Host support (allows to connect external keyboard, mouse, storage, network
etc).
• wayland: Include the Wayland display server protocol and the library that supports it.

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Features

• wifi: Include WiFi support (integrated only).
• x11: Include the X server and libraries.

11.3. Image Features
The contents of images generated by the OpenEmbedded build system can be controlled by the
IMAGE_FEATURES and EXTRA_IMAGE_FEATURES variables that you typically configure in your image
recipes. Through these variables, you can add several different predefined packages such as
development utilities or packages with debug information needed to investigate application problems
or profile applications.
The following image features are available for all images:
• dbg-pkgs: Installs debug symbol packages for all packages installed in a given image.
• debug-tweaks: Makes an image suitable for development (e.g. allows root logins without
passwords).
• dev-pkgs: Installs development packages (headers and extra library links) for all packages installed
in a given image.
• doc-pkgs: Installs documentation packages for all packages installed in a given image.
• package-management: Installs package management tools and preserves the package manager
database.
• ptest-pkgs: Installs ptest packages for all ptest-enabled recipes.
• read-only-rootfs: Creates an image whose root filesystem is read-only. See the
"Creating a Read-Only Root Filesystem [http://www.yoctoproject.org/docs/1.8/dev-manual/devmanual.html#creating-a-read-only-root-filesystem]" section in the Yocto Project Development
Manual for more information.
• splash: Enables showing a splash screen during boot. By default, this screen is provided by psplash,
which does allow customization. If you prefer to use an alternative splash screen package, you can
do so by setting the SPLASH variable to a different package name (or names) within the image
recipe or at the distro configuration level.
• staticdev-pkgs: Installs static development packages, which are static libraries (i.e. *.a files), for
all packages installed in a given image.
Some image features are available only when you inherit the core-image class. The current list of
these valid features is as follows:
• eclipse-debug: Provides Eclipse remote debugging support.
• hwcodecs: Installs hardware acceleration codecs.
• nfs-server: Installs an NFS server.
• qt4-pkgs: Supports Qt4/X11 and demo applications.
• ssh-server-dropbear: Installs the Dropbear minimal SSH server.
• ssh-server-openssh: Installs the OpenSSH SSH server, which is more full-featured than Dropbear.
Note that if both the OpenSSH SSH server and the Dropbear minimal SSH server are present in
IMAGE_FEATURES, then OpenSSH will take precedence and Dropbear will not be installed.
• tools-debug: Installs debugging tools such as strace and gdb. For information on GDB, see
the "Debugging With the GNU Project Debugger (GDB) Remotely [http://www.yoctoproject.org/
docs/1.8/dev-manual/dev-manual.html#platdev-gdb-remotedebug]" section in the Yocto Project
Development Manual. For information on tracing and profiling, see the Yocto Project Profiling and
Tracing Manual [http://www.yoctoproject.org/docs/1.8/profile-manual/profile-manual.html].
• tools-profile: Installs profiling tools such as oprofile, exmap, and LTTng. For general information
on user-space tools, see the "User-Space Tools [http://www.yoctoproject.org/docs/1.8/adt-manual/
adt-manual.html#user-space-tools]" section in the Yocto Project Application Developer's Guide.

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Features

• tools-sdk: Installs a full SDK that runs on the device.
• tools-testapps: Installs device testing tools (e.g. touchscreen debugging).
• x11: Installs the X server.
• x11-base: Installs the X server with a minimal environment.
• x11-sato: Installs the OpenedHand Sato environment.

11.4. Feature Backfilling
Sometimes it is necessary in the OpenEmbedded build system to extend MACHINE_FEATURES or
DISTRO_FEATURES to control functionality that was previously enabled and not able to be disabled.
For these cases, we need to add an additional feature item to appear in one of these variables, but we
do not want to force developers who have existing values of the variables in their configuration to add
the new feature in order to retain the same overall level of functionality. Thus, the OpenEmbedded
build system has a mechanism to automatically "backfill" these added features into existing distro
or machine configurations. You can see the list of features for which this is done by finding
the DISTRO_FEATURES_BACKFILL and MACHINE_FEATURES_BACKFILL variables in the meta/conf/
bitbake.conf file.
Because such features are backfilled by default into all configurations as described in the previous
paragraph, developers who wish to disable the new features need to be able to selectively prevent
the backfilling from occurring. They can do this by adding the undesired feature or features to the
DISTRO_FEATURES_BACKFILL_CONSIDERED or MACHINE_FEATURES_BACKFILL_CONSIDERED variables
for distro features and machine features respectively.
Here are two examples to help illustrate feature backfilling:
• The "pulseaudio" distro feature option: Previously, PulseAudio support was enabled within the
Qt and GStreamer frameworks. Because of this, the feature is backfilled and thus enabled for
all distros through the DISTRO_FEATURES_BACKFILL variable in the meta/conf/bitbake.conf file.
However, your distro needs to disable the feature. You can disable the feature without affecting
other existing distro configurations that need PulseAudio support by adding "pulseaudio" to
DISTRO_FEATURES_BACKFILL_CONSIDERED in your distro's .conf file. Adding the feature to this
variable when it also exists in the DISTRO_FEATURES_BACKFILL variable prevents the build system
from adding the feature to your configuration's DISTRO_FEATURES, effectively disabling the feature
for that particular distro.
• The "rtc" machine feature option: Previously, real time clock (RTC) support was enabled for
all target devices. Because of this, the feature is backfilled and thus enabled for all machines
through the MACHINE_FEATURES_BACKFILL variable in the meta/conf/bitbake.conf file. However,
your target device does not have this capability. You can disable RTC support for your device
without affecting other machines that need RTC support by adding the feature to your machine's
MACHINE_FEATURES_BACKFILL_CONSIDERED list in the machine's .conf file. Adding the feature to
this variable when it also exists in the MACHINE_FEATURES_BACKFILL variable prevents the build
system from adding the feature to your configuration's MACHINE_FEATURES, effectively disabling
RTC support for that particular machine.

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Chapter 12. Variables Glossary
This chapter lists common variables used in the OpenEmbedded build system and gives an overview
of their function and contents.

Glossary
ABCDEFGHIKLMOPQRSTUWX

A
Extension to the Application Binary Interface (ABI) field of the GNU
canonical architecture name (e.g. "eabi").

ABIEXTENSION

ABI extensions are set in the machine include files. For example,
the meta/conf/machine/include/arm/arch-arm.inc file sets the
following extension:
ABIEXTENSION = "eabi"
Specifies if an output package should still be produced if it is empty.
By default, BitBake does not produce empty packages. This default
behavior can cause issues when there is an RDEPENDS or some other
hard runtime requirement on the existence of the package.

ALLOW_EMPTY

Like all package-controlling variables, you must always use them in
conjunction with a package name override, as in:
ALLOW_EMPTY_${PN} = "1"
ALLOW_EMPTY_${PN}-dev = "1"
ALLOW_EMPTY_${PN}-staticdev = "1"

ALTERNATIVE

Lists commands in a package that need an alternative binary naming
scheme. Sometimes the same command is provided in multiple
packages. When this occurs, the OpenEmbedded build system needs
to use the alternatives system to create a different binary naming
scheme so the commands can co-exist.
To use the variable, list out the package's commands that also exist
as part of another package. For example, if the busybox package
has four commands that also exist as part of another package, you
identify them as follows:
ALTERNATIVE_busybox = "sh sed test bracket"
For more information on the alternatives system, see the "updatealternatives.bbclass" section.

Used by the alternatives system to map duplicated commands to
actual locations. For example, if the bracket command provided by
the busybox package is duplicated through another package, you
must use the ALTERNATIVE_LINK_NAME variable to specify the actual
location:
ALTERNATIVE_LINK_NAME
ALTERNATIVE_LINK_NAME[bracket] = "/usr/bin/["
124

Variables Glossary

In this example, the binary for the bracket command (i.e. [) from
the busybox package resides in /usr/bin/.

Note
If ALTERNATIVE_LINK_NAME is not defined, it defaults to
${bindir}/name.
For more information on the alternatives system, see the "updatealternatives.bbclass" section.
Used by the alternatives system to create default priorities for
duplicated commands. You can use the variable to create a single
default regardless of the command name or package, a default for
specific duplicated commands regardless of the package, or a default
for specific commands tied to particular packages. Here are the
ALTERNATIVE_PRIORITY
available syntax forms:
ALTERNATIVE_PRIORITY = "priority"
ALTERNATIVE_PRIORITY[name] = "priority"
ALTERNATIVE_PRIORITY_pkg[name] = "priority"
For more information on the alternatives system, see the "updatealternatives.bbclass" section.
Used by the alternatives system to create default link locations
for duplicated commands. You can use the variable to create a
single default location for all duplicated commands regardless of
the command name or package, a default for specific duplicated
commands regardless of the package, or a default for specific
ALTERNATIVE_TARGET
commands tied to particular packages. Here are the available syntax
forms:
ALTERNATIVE_TARGET = "target"
ALTERNATIVE_TARGET[name] = "target"
ALTERNATIVE_TARGET_pkg[name] = "target"

Note
If ALTERNATIVE_TARGET is not defined, it inherits the value
from the ALTERNATIVE_LINK_NAME variable.
If ALTERNATIVE_LINK_NAME and ALTERNATIVE_TARGET are
the same, the target for ALTERNATIVE_TARGET has ".{BPN}"
appended to it.
Finally, if the file referenced has not been renamed, the
alternatives system will rename it to avoid the need to
rename alternative files in the do_install task while
retaining support for the command if necessary.
For more information on the alternatives system, see the "updatealternatives.bbclass" section.
An override list of append strings for each LABEL.
See the grub-efi class for more information on how this variable is
used.
APPEND
125

Variables Glossary

Lists recipe names (PN values) BitBake does not attempt to build.
Instead, BitBake assumes these recipes have already been built.
In OpenEmbedded Core, ASSUME_PROVIDED mostly specifies native
tools that should not be built. An example is git-native, which when
ASSUME_PROVIDED
specified, allows for the Git binary from the host to be used rather
than building git-native.
The email address used to contact the original author or authors in
order to send patches and forward bugs.

AUTHOR
Enables creating an automatic menu for the syslinux bootloader. You
must set this variable in your recipe. The syslinux class checks this
variable.
AUTO_SYSLINUXMENU
When SRCREV is set to the value of this variable, it specifies to use
the latest source revision in the repository. Here is an example:

AUTOREV

SRCREV = "${AUTOREV}"
The list of defined CPU and Application Binary Interface (ABI) tunings
(i.e. "tunes") available for use by the OpenEmbedded build system.

AVAILTUNES

The
list
simply
presents
the
tunes
that
are
available. Not all tunes may be compatible with a
particular machine configuration, or with each other in
a Multilib [http://www.yoctoproject.org/docs/1.8/dev-manual/devmanual.html#combining-multiple-versions-library-files-into-oneimage] configuration.
To add a tune to the list, be sure to append it with
spaces using the "+=" BitBake operator. Do not simply
replace the list by using the "=" operator. See the "Basic
Syntax [http://www.yoctoproject.org/docs/1.8/bitbake-user-manual/
bitbake-user-manual.html#basic-syntax]" section in the BitBake
User Manual for more information.

B

B

The directory within the Build Directory [http://www.yoctoproject.org/
docs/1.8/dev-manual/dev-manual.html#build-directory] in which the
OpenEmbedded build system places generated objects during a
recipe's build process. By default, this directory is the same as the S
directory, which is defined as:
S = "${WORKDIR}/${BP}/"
You can separate the (S) directory and the directory pointed to by the
B variable. Most Autotools-based recipes support separating these
directories. The build system defaults to using separate directories
for gcc and some kernel recipes.

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Variables Glossary

Lists "recommended-only" packages to not install. Recommendedonly packages are packages installed only through the RRECOMMENDS
variable. You can prevent any of these "recommended" packages
from being installed by listing them with the BAD_RECOMMENDATIONS
variable:
BAD_RECOMMENDATIONS

BAD_RECOMMENDATIONS = "package_name package_name package_name ..."
You can set this variable globally in your local.conf file or you can
attach it to a specific image recipe by using the recipe name override:
BAD_RECOMMENDATIONS_pn-target_image = "package_name"
It is important to realize that if you choose to not install packages
using this variable and some other packages are dependent on them
(i.e. listed in a recipe's RDEPENDS variable), the OpenEmbedded build
system ignores your request and will install the packages to avoid
dependency errors.
Support for this variable exists only when using the IPK and RPM
packaging backend. Support does not exist for DEB.
See the NO_RECOMMENDATIONS and the PACKAGE_EXCLUDE variables
for related information.

BASE_LIB

The library directory name for the CPU or Application Binary
Interface (ABI) tune. The BASE_LIB applies only in the Multilib
context. See the "Combining Multiple Versions of Library Files into
One Image [http://www.yoctoproject.org/docs/1.8/dev-manual/devmanual.html#combining-multiple-versions-library-files-into-oneimage]" section in the Yocto Project Development Manual for
information on Multilib.
The BASE_LIB variable is defined in the machine include files in the
Source Directory [http://www.yoctoproject.org/docs/1.8/dev-manual/
dev-manual.html#source-directory]. If Multilib is not being used, the
value defaults to "lib".

Defines how BitBake handles situations where an append file
(.bbappend) has no corresponding recipe file (.bb). This condition
often occurs when layers get out of sync (e.g. oe-core bumps a
recipe version and the old recipe no longer exists and the other layer
has not been updated to the new version of the recipe yet).
BB_DANGLINGAPPENDS_WARNONLY
The default fatal behavior is safest because it is the sane reaction
given something is out of sync. It is important to realize when your
changes are no longer being applied.
You can change the default behavior by setting this variable to "1",
"yes", or "true" in your local.conf file, which is located in the
Build Directory [http://www.yoctoproject.org/docs/1.8/dev-manual/
dev-manual.html#build-directory]: Here is an example:
BB_DANGLINGAPPENDS_WARNONLY = "1"
Monitors disk space and available inodes during the build and allows
you to control the build based on these parameters.
Disk space monitoring is disabled by default. To enable monitoring,
add the BB_DISKMON_DIRS variable to your conf/local.conf file
BB_DISKMON_DIRS
found in the Build Directory [http://www.yoctoproject.org/docs/1.8/

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Variables Glossary

dev-manual/dev-manual.html#build-directory]. Use the following
form:
BB_DISKMON_DIRS = "action,dir,threshold [...]"
where:
action is:
ABORT:

Immediately abort the build when
a threshold is broken.
STOPTASKS: Stop the build after the currently
executing tasks have finished when
a threshold is broken.
WARN:
Issue a warning but continue the
build when a threshold is broken.
Subsequent warnings are issued as
defined by the
BB_DISKMON_WARNINTERVAL variable,
which must be defined in the
conf/local.conf file.

dir is:
Any directory you choose. You can specify one or
more directories to monitor by separating the
groupings with a space. If two directories are
on the same device, only the first directory
is monitored.
threshold is:
Either the minimum available disk space,
the minimum number of free inodes, or
both. You must specify at least one. To
omit one or the other, simply omit the value.
Specify the threshold using G, M, K for Gbytes,
Mbytes, and Kbytes, respectively. If you do
not specify G, M, or K, Kbytes is assumed by
default. Do not use GB, MB, or KB.
Here are some examples:

BB_DISKMON_DIRS = "ABORT,${TMPDIR},1G,100K WARN,${SSTATE_DIR},1G,1
BB_DISKMON_DIRS = "STOPTASKS,${TMPDIR},1G"
BB_DISKMON_DIRS = "ABORT,${TMPDIR},,100K"
The first example works only if you also provide the
BB_DISKMON_WARNINTERVAL variable in the conf/local.conf. This
example causes the build system to immediately abort when either
the disk space in ${TMPDIR} drops below 1 Gbyte or the available
free inodes drops below 100 Kbytes. Because two directories are
provided with the variable, the build system also issue a warning
when the disk space in the ${SSTATE_DIR} directory drops below
1 Gbyte or the number of free inodes drops below 100 Kbytes.
Subsequent warnings are issued during intervals as defined by the
BB_DISKMON_WARNINTERVAL variable.
The second example stops the build after all currently executing tasks
complete when the minimum disk space in the ${TMPDIR} directory
drops below 1 Gbyte. No disk monitoring occurs for the free inodes
in this case.

128

Variables Glossary

The final example immediately aborts the build when the number of
free inodes in the ${TMPDIR} directory drops below 100 Kbytes. No
disk space monitoring for the directory itself occurs in this case.
Defines the disk space and free inode warning intervals. To set
these intervals, define the variable in your conf/local.conf file
in the Build Directory [http://www.yoctoproject.org/docs/1.8/devmanual/dev-manual.html#build-directory].
BB_DISKMON_WARNINTERVAL
If you are going to use the BB_DISKMON_WARNINTERVAL variable, you
must also use the BB_DISKMON_DIRS variable and define its action as
"WARN". During the build, subsequent warnings are issued each time
disk space or number of free inodes further reduces by the respective
interval.
If you do not provide a BB_DISKMON_WARNINTERVAL variable and
you do use BB_DISKMON_DIRS with the "WARN" action, the disk
monitoring interval defaults to the following:
BB_DISKMON_WARNINTERVAL = "50M,5K"
When specifying the variable in your configuration file, use the
following form:

BB_DISKMON_WARNINTERVAL = "disk_space_interval,disk_inode_interval
where:
disk_space_interval is:
An interval of memory expressed in either
G, M, or K for Gbytes, Mbytes, or Kbytes,
respectively. You cannot use GB, MB, or KB.
disk_inode_interval is:
An interval of free inodes expressed in either
G, M, or K for Gbytes, Mbytes, or Kbytes,
respectively. You cannot use GB, MB, or KB.
Here is an example:
BB_DISKMON_DIRS = "WARN,${SSTATE_DIR},1G,100K"
BB_DISKMON_WARNINTERVAL = "50M,5K"
These variables cause the OpenEmbedded build system to issue
subsequent warnings each time the available disk space further
reduces by 50 Mbytes or the number of free inodes further reduces
by 5 Kbytes in the ${SSTATE_DIR} directory. Subsequent warnings
based on the interval occur each time a respective interval is reached
beyond the initial warning (i.e. 1 Gbytes and 100 Kbytes).
Causes tarballs of the Git repositories, including the Git metadata, to
be placed in the DL_DIR directory.
For performance reasons, creating and placing tarballs of the Git
repositories is not the default action by the OpenEmbedded build
BB_GENERATE_MIRROR_TARBALLS
system.
BB_GENERATE_MIRROR_TARBALLS = "1"

129

Variables Glossary

Set
this
variable
in
your
local.conf
file
in
the
Build Directory [http://www.yoctoproject.org/docs/1.8/dev-manual/
dev-manual.html#build-directory].
The maximum number of tasks BitBake should run in parallel at any
one time. If your host development system supports multiple cores,
a good rule of thumb is to have this variable be twice the number
of cores.
BB_NUMBER_THREADS
The default value for BB_NUMBER_THREADS is equal to the number of
cores your build system has.
Allows you to extend a recipe so that it builds variants of the software.
Common variants for recipes exist such as "natives" like quiltnative, which is a copy of Quilt built to run on the build system;
"crosses" such as gcc-cross, which is a compiler built to run on the
build machine but produces binaries that run on the target MACHINE;
BBCLASSEXTEND
"nativesdk", which targets the SDK machine instead of MACHINE; and
"mulitlibs" in the form "multilib:multilib_name".
To build a different variant of the recipe with a minimal amount of
code, it usually is as simple as adding the following to your recipe:
BBCLASSEXTEND =+ "native nativesdk"
BBCLASSEXTEND =+ "multilib:multilib_name"
Lists the names of configured layers. These names are used to find
the other BBFILE_* variables. Typically, each layer will append its
name to this variable in its conf/layer.conf file.
BBFILE_COLLECTIONS
Variable that expands to match files from BBFILES in a particular
layer. This variable is used in the conf/layer.conf file and
must be suffixed with the name of the specific layer (e.g.
BBFILE_PATTERN_emenlow).
BBFILE_PATTERN
Assigns the priority for recipe files in each layer.
This variable is useful in situations where the same recipe appears
in more than one layer. Setting this variable allows you to prioritize a
layer against other layers that contain the same recipe - effectively
BBFILE_PRIORITY
letting you control the precedence for the multiple layers. The
precedence established through this variable stands regardless of a
recipe's version (PV variable). For example, a layer that has a recipe
with a higher PV value but for which the BBFILE_PRIORITY is set to
have a lower precedence still has a lower precedence.
A larger value for the BBFILE_PRIORITY variable results in a higher
precedence. For example, the value 6 has a higher precedence than
the value 5. If not specified, the BBFILE_PRIORITY variable is set
based on layer dependencies (see the LAYERDEPENDS variable for
more information. The default priority, if unspecified for a layer with
no dependencies, is the lowest defined priority + 1 (or 1 if no priorities
are defined).

Tip
You can use the command bitbake-layers show-layers to
list all configured layers along with their priorities.

130

Variables Glossary

List of recipe files used by BitBake to build software.

BBFILES
Variable that controls how BitBake displays logs on build failure.

BBINCLUDELOGS
Lists the layers to enable during the build. This variable
is defined in the bblayers.conf configuration file in the
Build Directory [http://www.yoctoproject.org/docs/1.8/dev-manual/
dev-manual.html#build-directory]. Here is an example:
BBLAYERS
BBLAYERS = " \
/home/scottrif/poky/meta \
/home/scottrif/poky/meta-yocto \
/home/scottrif/poky/meta-yocto-bsp \
/home/scottrif/poky/meta-mykernel \
"
BBLAYERS_NON_REMOVABLE ?= " \
/home/scottrif/poky/meta \
/home/scottrif/poky/meta-yocto \
"
This example enables four layers, one of which is a custom, userdefined layer named meta-mykernel.
Lists core layers that cannot be removed from the bblayers.conf
file during a build using the Hob [https://www.yoctoproject.org/toolsresources/projects/hob].

Note
BBLAYERS_NON_REMOVABLE
When building an image outside of Hob, this variable is
ignored.
In order for BitBake to build your image using Hob, your
bblayers.conf file must include the meta and meta-yocto core
layers. Here is an example that shows these two layers listed in the
BBLAYERS_NON_REMOVABLE statement:
BBLAYERS = " \
/home/scottrif/poky/meta \
/home/scottrif/poky/meta-yocto \
/home/scottrif/poky/meta-yocto-bsp \
/home/scottrif/poky/meta-mykernel \
"
BBLAYERS_NON_REMOVABLE ?= " \
/home/scottrif/poky/meta \
/home/scottrif/poky/meta-yocto \
"

131

Variables Glossary

Prevents BitBake from processing recipes and recipe append files.
Use the BBMASK variable from within the conf/local.conf file
found in the Build Directory [http://www.yoctoproject.org/docs/1.8/
dev-manual/dev-manual.html#build-directory].
BBMASK

You can use the BBMASK variable to "hide" these .bb and .bbappend
files. BitBake ignores any recipe or recipe append files that match the
expression. It is as if BitBake does not see them at all. Consequently,
matching files are not parsed or otherwise used by BitBake.
The value you provide is passed to Python's regular expression
compiler. The expression is compared against the full paths to the
files. For complete syntax information, see Python's documentation
at http://docs.python.org/release/2.3/lib/re-syntax.html.
The following example uses a complete regular expression to tell
BitBake to ignore all recipe and recipe append files in the meta-ti/
recipes-misc/ directory:
BBMASK = "meta-ti/recipes-misc/"
If you want to mask out multiple directories or recipes, use the
vertical bar to separate the regular expression fragments. This next
example masks out multiple directories and individual recipes:
BBMASK
BBMASK
BBMASK
BBMASK
BBMASK

= "meta-ti/recipes-misc/|meta-ti/recipes-ti/packagegroup/"
.= "|.*meta-oe/recipes-support/"
.= "|.*openldap"
.= "|.*opencv"
.= "|.*lzma"

Notice how the vertical bar is used to append the fragments.

Note
When specifying a directory name, use the trailing slash
character to ensure you match just that directory name.
Used by BitBake to locate .bbclass and configuration files. This
variable is analogous to the PATH variable.

Note
BBPATH

If you run BitBake from a directory outside of the
Build Directory [http://www.yoctoproject.org/docs/1.8/devmanual/dev-manual.htmlbuild-directory], you must be sure
to set BBPATH to point to the Build Directory. Set the variable
as you would any environment variable and then run BitBake:
$ BBPATH = "build_directory"
$ export BBPATH
$ bitbake target
Points to the server that runs memory-resident BitBake. This variable
is set by the oe-init-build-env-memres setup script and should not
be hand-edited. The variable is only used when you employ memoryresident BitBake. The setup script exports the value as follows:

BBSERVER
export BBSERVER=localhost:$port
132

Variables Glossary

For more information on how the BBSERVER is used, see
the oe-init-build-env-memres script, which is located in the
Source Directory [http://www.yoctoproject.org/docs/1.8/dev-manual/
dev-manual.html#source-directory].

BINCONFIG

When inheriting the binconfig-disabled class, this variable
specifies binary configuration scripts to disable in favor of using pkgconfig to query the information. The binconfig-disabled class will
modify the specified scripts to return an error so that calls to them
can be easily found and replaced.
To add multiple scripts, separate them by spaces. Here is an example
from the libpng recipe:
BINCONFIG = "${bindir}/libpng-config ${bindir}/libpng16-config"

BINCONFIG_GLOB

When inheriting the binconfig class, this variable specifies a
wildcard for configuration scripts that need editing. The scripts are
edited to correct any paths that have been set up during compilation
so that they are correct for use when installed into the sysroot and
called by the build processes of other recipes.
For
more
information
on
how
this
variable
works,
see
meta/classes/binconfig.bbclass
in
the
Source
Directory
[http://www.yoctoproject.org/docs/1.8/dev-manual/devmanual.html#source-directory]. You can also find general
information on the class in the "binconfig.bbclass" section.
The base recipe name and version but without any special recipe
name suffix (i.e. -native, lib64-, and so forth). BP is comprised of
the following:

BP

BPN

${BPN}-${PV}
The bare name of the recipe. This variable is a version of the PN
variable but removes common suffixes such as "-native" and "cross" as well as removes common prefixes such as multilib's "lib64-"
and "lib32-". The exact list of suffixes removed is specified by the
SPECIAL_PKGSUFFIX variable. The exact list of prefixes removed
is specified by the MLPREFIX variable. Prefixes are removed for
multilib and nativesdk cases.
Specifies a URL for an upstream bug tracking website for a recipe.
The OpenEmbedded build system does not use this variable. Rather,
the variable is a useful pointer in case a bug in the software being
built needs to be manually reported.

BUGTRACKER
Specifies the flags to pass to the C compiler when building for the
build host. When building in the -native context, CFLAGS is set to
the value of this variable by default.
BUILD_CFLAGS
Specifies the flags to pass to the C pre-processor (i.e. to both the
C and the C++ compilers) when building for the build host. When
building in the native context, CPPFLAGS is set to the value of this
variable by default.
BUILD_CPPFLAGS

133

Variables Glossary

Specifies the flags to pass to the C++ compiler when building for the
build host. When building in the native context, CXXFLAGS is set to
the value of this variable by default.
BUILD_CXXFLAGS
Specifies the flags to pass to the linker when building for the build
host. When building in the -native context, LDFLAGS is set to the
value of this variable by default.
BUILD_LDFLAGS
Specifies the optimization flags passed to the C compiler when
building for the build host or the SDK. The flags are passed through
the BUILD_CFLAGS and BUILDSDK_CFLAGS default values.
The default value of the BUILD_OPTIMIZATION variable is "-O2 -pipe".
BUILD_OPTIMIZATION

BUILDDIR

Points
to
the
location
of
the
Build
Directory
[http://www.yoctoproject.org/docs/1.8/dev-manual/devmanual.html#build-directory]. You can define this directory indirectly
through the oe-init-build-env and oe-init-build-env-memres
scripts by passing in a Build Directory path when you run the scripts.
If you run the scripts and do not provide a Build Directory path, the
BUILDDIR defaults to build in the current directory.

When inheriting the buildhistory class, this variable specifies
whether or not to commit the build history output in a local Git
repository. If set to "1", this local repository will be maintained
automatically by the buildhistory class and a commit will be
created on every build for changes to each top-level subdirectory of
BUILDHISTORY_COMMIT
the build history output (images, packages, and sdk). If you want to
track changes to build history over time, you should set this value
to "1".
By default, the buildhistory class does not commit the build history
output in a local Git repository:
BUILDHISTORY_COMMIT ?= "0"
When inheriting the buildhistory class, this variable
specifies the author to use for each Git commit. In order
for the BUILDHISTORY_COMMIT_AUTHOR variable to work, the
BUILDHISTORY_COMMIT variable must be set to "1".
BUILDHISTORY_COMMIT_AUTHOR
Git
requires
that
the
value
you
provide
for
the
BUILDHISTORY_COMMIT_AUTHOR variable takes the form of "name
". Providing an email address or host that is not valid
does not produce an error.
By default, the buildhistory class sets the variable as follows:

BUILDHISTORY_COMMIT_AUTHOR ?= "buildhistory /.scc file. For example, from the meta branch in
the linux-yocto-3.0 kernel, the meta/cfg/kernel-cache/bsp/
cedartrail/cedartrail-standard.scc file has the following:
define KMACHINE cedartrail
define KTYPE standard
define KARCH i386
include ktypes/standard
branch cedartrail
include cedartrail.scc
You can see that the kernel understands the machine name for the
Cedar Trail Board Support Package (BSP) as cedartrail.
If you look in the Cedar Trail BSP layer in the meta-intel Source
Repositories [http://www.yoctoproject.org/docs/1.8/dev-manual/devmanual.html#source-repositories] at meta-cedartrail/recipeskernel/linux/linux-yocto_3.0.bbappend, you will find the
following statements among others:

COMPATIBLE_MACHINE_cedartrail = "cedartrail"
KMACHINE_cedartrail = "cedartrail"
KBRANCH_cedartrail = "yocto/standard/cedartrail"
KERNEL_FEATURES_append_cedartrail += "bsp/cedartrail/cedartrail-pv
KERNEL_FEATURES_append_cedartrail += "cfg/efi-ext.scc"
COMPATIBLE_MACHINE_cedartrail-nopvr = "cedartrail"
KMACHINE_cedartrail-nopvr = "cedartrail"
KBRANCH_cedartrail-nopvr = "yocto/standard/cedartrail"
KERNEL_FEATURES_append_cedartrail-nopvr += " cfg/smp.scc"
The KMACHINE statements in the kernel's append file make sure
that the OpenEmbedded build system and the Yocto Linux kernel
understand the same machine names.
This append file uses two KMACHINE statements. The first is not
really necessary but does ensure that the machine known to the
OpenEmbedded build system as cedartrail maps to the machine
in the kernel also known as cedartrail:
KMACHINE_cedartrail

= "cedartrail"

The second statement is a good example of why the KMACHINE
variable is needed. In this example, the OpenEmbedded build system
uses the cedartrail-nopvr machine name to refer to the Cedar Trail
BSP that does not support the proprietary PowerVR driver. The kernel,
however, uses the machine name cedartrail. Thus, the append
file must map the cedartrail-nopvr machine name to the kernel's
cedartrail name:
KMACHINE_cedartrail-nopvr

166

= "cedartrail"

Variables Glossary

BSPs that ship with the Yocto Project release provide all mappings
between the Yocto Project kernel machine names and the
OpenEmbedded machine names. Be sure to use the KMACHINE if you
create a BSP and the machine name you use is different than that
used in the kernel.

KTYPE

Defines the kernel type to be used in assembling the configuration.
The linux-yocto recipes define "standard", "tiny", and "preempt-rt"
kernel types. See the "Kernel Types [http://www.yoctoproject.org/
docs/1.8/kernel-dev/kernel-dev.html#kernel-types]" section in the
Yocto Project Linux Kernel Development Manual for more information
on kernel types.
You
define
the
KTYPE
variable
in
the
BSP Descriptions [http://www.yoctoproject.org/docs/1.8/kernel-dev/
kernel-dev.html#bsp-descriptions]. The value you use must match
the value used for the LINUX_KERNEL_TYPE value used by the kernel
recipe.

L
Provides a list of targets for automatic configuration.
See the grub-efi class for more information on how this variable is
used.
LABELS

LAYERDEPENDS

Lists the layers that this recipe depends upon, separated by
spaces. Optionally, you can specify a specific layer version for
a dependency by adding it to the end of the layer name
with a colon, (e.g. "anotherlayer:3" to be compared against
LAYERVERSION_anotherlayer in this case). An error will be produced
if any dependency is missing or the version numbers do not match
exactly (if specified). This variable is used in the conf/layer.conf
file and must be suffixed with the name of the specific layer (e.g.
LAYERDEPENDS_mylayer).
When used inside the layer.conf configuration file, this variable
provides the path of the current layer. This variable is not available
outside of layer.conf and references are expanded immediately
when parsing of the file completes.

LAYERDIR

LAYERVERSION

Optionally specifies the version of a layer as a single number. You can
use this within LAYERDEPENDS for another layer in order to depend
on a specific version of the layer. This variable is used in the conf/
layer.conf file and must be suffixed with the name of the specific
layer (e.g. LAYERVERSION_mylayer).
Specifies the flags to pass to the linker. This variable is exported to
an environment variable and thus made visible to the software being
built during the compilation step.

LDFLAGS

Default initialization for LDFLAGS varies depending on what is being
built:
• TARGET_LDFLAGS when building for the target
• BUILD_LDFLAGS when building for the build host (i.e. -native)
• BUILDSDK_LDFLAGS when building for an SDK (i.e. nativesdk-)

167

Variables Glossary

Specifies the lead (or primary) compiled library file (.so) that the
debian class applies its naming policy to given a recipe that packages
multiple libraries.
LEAD_SONAME

This variable works in conjunction with the debian class.
Checksums of the license text in the recipe source code.

This variable tracks changes in license text of the source code files. If
the license text is changed, it will trigger a build failure, which gives
the developer an opportunity to review any license change.
LIC_FILES_CHKSUM
This variable must be defined for all recipes (unless LICENSE is set
to "CLOSED").
For more information, see the " Tracking License Changes" section.
The list of source licenses for the recipe. Follow these rules:
• Do not use spaces within individual license names.
LICENSE

• Separate license names using | (pipe) when there is a choice
between licenses.
• Separate license names using & (ampersand) when multiple
licenses exist that cover different parts of the source.
• You can use spaces between license names.
• For standard licenses, use the names of the files in meta/files/
common-licenses/ or the SPDXLICENSEMAP flag names defined in
meta/conf/licenses.conf.
Here are some examples:
LICENSE = "LGPLv2.1 | GPLv3"
LICENSE = "MPL-1 & LGPLv2.1"
LICENSE = "GPLv2+"
The first example is from the recipes for Qt, which the user may
choose to distribute under either the LGPL version 2.1 or GPL version
3. The second example is from Cairo where two licenses cover
different parts of the source code. The final example is from sysstat,
which presents a single license.
You can also specify licenses on a per-package basis to handle
situations where components of the output have different licenses.
For example, a piece of software whose code is licensed under GPLv2
but has accompanying documentation licensed under the GNU Free
Documentation License 1.2 could be specified as follows:
LICENSE = "GFDL-1.2 & GPLv2"
LICENSE_${PN} = "GPLv2"
LICENSE_${PN}-doc = "GFDL-1.2"
Specifies additional flags for a recipe you must whitelist through
LICENSE_FLAGS_WHITELIST in order to allow the recipe to be built.
When providing multiple flags, separate them with spaces.

LICENSE_FLAGS

This value is independent of LICENSE and is typically used to mark
recipes that might require additional licenses in order to be used
in a commercial product. For more information, see the "Enabling
Commercially Licensed Recipes" section.

168

Variables Glossary

Lists license flags that when specified in LICENSE_FLAGS within a
recipe should not prevent that recipe from being built. This practice is
otherwise known as "whitelisting" license flags. For more information,
see the Enabling Commercially Licensed Recipes" section.
LICENSE_FLAGS_WHITELIST

LICENSE_PATH

Path to additional licenses used during the build. By default, the
OpenEmbedded build system uses COMMON_LICENSE_DIR to define
the directory that holds common license text used during the build.
The LICENSE_PATH variable allows you to extend that location to
other areas that have additional licenses:
LICENSE_PATH += "path-to-additional-common-licenses"

Defines the kernel type to be used in assembling the configuration.
The linux-yocto recipes define "standard", "tiny", and "preempt-rt"
kernel types. See the "Kernel Types [http://www.yoctoproject.org/
docs/1.8/kernel-dev/kernel-dev.html#kernel-types]" section in the
Yocto Project Linux Kernel Development Manual for more information
LINUX_KERNEL_TYPE
on kernel types.
If you do not specify a LINUX_KERNEL_TYPE, it defaults to "standard".
Together with KMACHINE, the LINUX_KERNEL_TYPE variable defines
the search arguments used by the kernel tools to find the appropriate
description within the kernel Metadata [http://www.yoctoproject.org/
docs/1.8/dev-manual/dev-manual.html#metadata] with which to
build out the sources and configuration.

LINUX_VERSION

The Linux version from kernel.org on which the Linux kernel image
being built using the OpenEmbedded build system is based. You
define this variable in the kernel recipe. For example, the linuxyocto-3.4.bb kernel recipe found in meta/recipes-kernel/linux
defines the variables as follows:
LINUX_VERSION ?= "3.4.24"
The LINUX_VERSION variable is used to define PV for the recipe:
PV = "${LINUX_VERSION}+git${SRCPV}"
A string extension compiled into the version string of the Linux kernel
built with the OpenEmbedded build system. You define this variable
in the kernel recipe. For example, the linux-yocto kernel recipes all
define the variable as follows:

LINUX_VERSION_EXTENSION
LINUX_VERSION_EXTENSION ?= "-yocto-${LINUX_KERNEL_TYPE}"
Defining this variable essentially sets the Linux kernel configuration
item CONFIG_LOCALVERSION, which is visible through the uname
command. Here is an example that shows the extension assuming it
was set as previously shown:
$ uname -r
3.7.0-rc8-custom

169

Variables Glossary

Specifies the directory to which the OpenEmbedded build system
writes overall log files. The default directory is ${TMPDIR}/log.

LOG_DIR

For the directory containing logs specific to each task, see the T
variable.

M

MACHINE

Specifies the target device for which the image is built.
You define MACHINE in the local.conf file found in the
Build Directory [http://www.yoctoproject.org/docs/1.8/dev-manual/
dev-manual.html#build-directory]. By default, MACHINE is set to
"qemux86", which is an x86-based architecture machine to be
emulated using QEMU:
MACHINE ?= "qemux86"
The variable corresponds to a machine configuration file of the same
name, through which machine-specific configurations are set. Thus,
when MACHINE is set to "qemux86" there exists the corresponding
qemux86.conf machine configuration file, which can be found in the
Source Directory [http://www.yoctoproject.org/docs/1.8/dev-manual/
dev-manual.html#source-directory] in meta/conf/machine.
The list of machines supported by the Yocto Project as shipped include
the following:
MACHINE
MACHINE
MACHINE
MACHINE
MACHINE
MACHINE
MACHINE
MACHINE
MACHINE
MACHINE

?=
?=
?=
?=
?=
?=
?=
?=
?=
?=

"qemuarm"
"qemumips"
"qemuppc"
"qemux86"
"qemux86-64"
"genericx86"
"genericx86-64"
"beaglebone"
"mpc8315e-rdb"
"edgerouter"

The last five are Yocto Project reference hardware boards, which are
provided in the meta-yocto-bsp layer.

Note
Adding additional Board Support Package (BSP) layers to your
configuration adds new possible settings for MACHINE.
Specifies the name of the machine-specific architecture. This variable
is set automatically from MACHINE or TUNE_PKGARCH. You should not
hand-edit the MACHINE_ARCH variable.
MACHINE_ARCH
A list of required machine-specific packages to install as part of the
image being built. The build process depends on these packages
being present. Furthermore, because this is a "machine essential"
variable, the list of packages are essential for the machine to boot.
The impact of this variable affects images based on packagegroupMACHINE_ESSENTIAL_EXTRA_RDEPENDS
core-boot, including the core-image-minimal image.
This
variable
is
similar
to
MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS
variable
with

170

the
the

Variables Glossary

exception that the image being built has a build dependency on the
variable's list of packages. In other words, the image will not build if
a file in this list is not found.
As an example, suppose the machine for which you are building
requires example-init to be run during boot to initialize the
hardware. In this case, you would use the following in the machine's
.conf configuration file:
MACHINE_ESSENTIAL_EXTRA_RDEPENDS += "example-init"
A list of recommended machine-specific packages to install as
part of the image being built. The build process does not depend
on these packages being present. However, because this is a
"machine essential" variable, the list of packages are essential for
the machine to boot. The impact of this variable affects images based
MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS
on packagegroup-core-boot, including the core-image-minimal
image.
This variable is similar to the MACHINE_ESSENTIAL_EXTRA_RDEPENDS
variable with the exception that the image being built does not
have a build dependency on the variable's list of packages. In other
words, the image will still build if a package in this list is not found.
Typically, this variable is used to handle essential kernel modules,
whose functionality may be selected to be built into the kernel rather
than as a module, in which case a package will not be produced.
Consider an example where you have a custom kernel where a
specific touchscreen driver is required for the machine to be usable.
However, the driver can be built as a module or into the kernel
depending on the kernel configuration. If the driver is built as a
module, you want it to be installed. But, when the driver is built into
the kernel, you still want the build to succeed. This variable sets up
a "recommends" relationship so that in the latter case, the build will
not fail due to the missing package. To accomplish this, assuming
the package for the module was called kernel-module-ab123, you
would use the following in the machine's .conf configuration file:
MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS += "kernel-module-ab123"
Some examples of these machine essentials are flash, screen,
keyboard, mouse, or touchscreen drivers (depending on the
machine).
A list of machine-specific packages to install as part of the image
being built that are not essential for the machine to boot. However,
the build process for more fully-featured images depends on the
packages being present.
MACHINE_EXTRA_RDEPENDS
This variable affects all images based on packagegroup-base, which
does not include the core-image-minimal or core-image-fullcmdline images.
The variable is similar to the MACHINE_EXTRA_RRECOMMENDS variable
with the exception that the image being built has a build dependency
on the variable's list of packages. In other words, the image will not
build if a file in this list is not found.
An example is a machine that has WiFi capability but is not essential
for the machine to boot the image. However, if you are building a
more fully-featured image, you want to enable the WiFi. The package
containing the firmware for the WiFi hardware is always expected to
171

Variables Glossary

exist, so it is acceptable for the build process to depend upon finding
the package. In this case, assuming the package for the firmware
was called wifidriver-firmware, you would use the following in the
.conf file for the machine:
MACHINE_EXTRA_RDEPENDS += "wifidriver-firmware"
A list of machine-specific packages to install as part of the image
being built that are not essential for booting the machine. The image
being built has no build dependency on this list of packages.
This variable affects only images based on packagegroup-base,
MACHINE_EXTRA_RRECOMMENDS
which does not include the core-image-minimal or core-imagefull-cmdline images.
This variable is similar to the MACHINE_EXTRA_RDEPENDS variable with
the exception that the image being built does not have a build
dependency on the variable's list of packages. In other words, the
image will build if a file in this list is not found.
An example is a machine that has WiFi capability but is not essential
For the machine to boot the image. However, if you are building a
more fully-featured image, you want to enable WiFi. In this case, the
package containing the WiFi kernel module will not be produced if
the WiFi driver is built into the kernel, in which case you still want the
build to succeed instead of failing as a result of the package not being
found. To accomplish this, assuming the package for the module was
called kernel-module-examplewifi, you would use the following in
the .conf file for the machine:
MACHINE_EXTRA_RRECOMMENDS += "kernel-module-examplewifi"
Specifies the list of hardware features the MACHINE is capable
of supporting. For related information on enabling features, see
the DISTRO_FEATURES, COMBINED_FEATURES, and IMAGE_FEATURES
variables.
MACHINE_FEATURES
For a list of hardware features supported by the Yocto Project as
shipped, see the "Machine Features" section.
Features to be added to MACHINE_FEATURES if not also present in
MACHINE_FEATURES_BACKFILL_CONSIDERED.
This variable is set in the meta/conf/bitbake.conf file. It is not
intended to be user-configurable. It is best to just reference the
MACHINE_FEATURES_BACKFILL
variable to see which machine features are being backfilled for all
machine configurations. See the "Feature backfilling" section for
more information.
Features from MACHINE_FEATURES_BACKFILL that should not be
backfilled (i.e. added to MACHINE_FEATURES) during the build. See the
"Feature backfilling" section for more information.
MACHINE_FEATURES_BACKFILL_CONSIDERED
Lists overrides specific to the current machine. By default, this list
includes the value of MACHINE. You can extend the list to apply
variable overrides for classes of machines. For example, all QEMU
emulated machines (e.g. qemuarm, qemux86, and so forth) include
a common file named meta/conf/machine/include/qemu.inc that
MACHINEOVERRIDES
prepends MACHINEOVERRIDES with the following variable override:

172

Variables Glossary

MACHINEOVERRIDES =. "qemuall:"
Applying an override like qemuall affects all QEMU emulated
machines elsewhere. Here is an example from the connman-conf
recipe:
SRC_URI_append_qemuall = "file://wired.config \
file://wired-setup \
"
The email address of the distribution maintainer.

MAINTAINER

MIRRORS

Specifies additional paths from which the OpenEmbedded build
system gets source code. When the build system searches for source
code, it first tries the local download directory. If that location fails,
the build system tries locations defined by PREMIRRORS, the upstream
source, and then locations specified by MIRRORS in that order.
Assuming your distribution (DISTRO) is "poky", the default value for
MIRRORS is defined in the conf/distro/poky.conf file in the metayocto Git repository.

MLPREFIX

Specifies a prefix has been added to PN to create a special version of
a recipe or package, such as a Multilib version. The variable is used
in places where the prefix needs to be added to or removed from a
the name (e.g. the BPN variable). MLPREFIX gets set when a prefix
has been added to PN.
This variable has been replaced by the KERNEL_MODULE_AUTOLOAD
variable. You should replace all occurrences of module_autoload with
additions to KERNEL_MODULE_AUTOLOAD, for example:

module_autoload

module_autoload_rfcomm = "rfcomm"
should now be replaced with:
KERNEL_MODULE_AUTOLOAD += "rfcomm"
See the KERNEL_MODULE_AUTOLOAD variable for more information.
Specifies
modprobe.d
[http://linux.die.net/man/5/modprobe.d]
syntax lines for inclusion in the /etc/modprobe.d/modname.conf
file.

module_conf

You can use this variable anywhere that it can be recognized by the
kernel recipe or out-of-tree kernel module recipe (e.g. a machine
configuration file, a distribution configuration file, an append file for
the recipe, or the recipe itself). If you use this variable, you must also
be sure to list the module name in the KERNEL_MODULE_AUTOLOAD
variable.
Here is the general syntax:
module_conf_module_name = "modprobe.d-syntax"

173

Variables Glossary

You must use the kernel module name override.
Run man modprobe.d in the shell to find out more information on the
exact syntax you want to provide with module_conf.
Including module_conf causes the OpenEmbedded build system to
populate the /etc/modprobe.d/modname.conf file with modprobe.d
syntax lines. Here is an example that adds the options arg1 and arg2
to a module named mymodule:
module_conf_mymodule = "options mymodule arg1=val1 arg2=val2"
For information on how to specify kernel modules to auto-load on
boot, see the KERNEL_MODULE_AUTOLOAD variable.
The base name of the kernel modules tarball. This variable is set in
the kernel class as follows:

MODULE_IMAGE_BASE_NAME ?= "modules-${PKGE}-${PKGV}-${PKGR}-${MACHI
MODULE_IMAGE_BASE_NAME
See the PKGE, PKGV, PKGR, MACHINE, and DATETIME variables for
additional information.
Controls creation of the modules-*.tgz file. Set this variable to "0" to
disable creation of this file, which contains all of the kernel modules
resulting from a kernel build.
MODULE_TARBALL_DEPLOY
Separates files for different machines such that you can build for
multiple target machines using the same output directories. See the
STAMP variable for an example.
MULTIMACH_TARGET_SYS

N
A string identifying the host distribution. Strings consist of the
host distributor ID followed by the release, as reported by the
lsb_release tool or as read from /etc/lsb-release. For example,
when running a build on Ubuntu 12.10, the value is "Ubuntu-12.10".
If this information is unable to be determined, the value resolves to
NATIVELSBSTRING
"Unknown".
This variable is used by default to isolate native shared state
packages for different distributions (e.g. to avoid problems with
glibc version incompatibilities). Additionally, the variable is checked
against SANITY_TESTED_DISTROS if that variable is set.
Prevents installation of all "recommended-only" packages.
Recommended-only packages are packages installed only through
the RRECOMMENDS variable). Setting the NO_RECOMMENDATIONS
variable to "1" turns this feature on:
NO_RECOMMENDATIONS
NO_RECOMMENDATIONS = "1"

174

Variables Glossary

You can set this variable globally in your local.conf file or you can
attach it to a specific image recipe by using the recipe name override:
NO_RECOMMENDATIONS_pn-target_image = "package_name"
It is important to realize that if you choose to not install packages
using this variable and some other packages are dependent on them
(i.e. listed in a recipe's RDEPENDS variable), the OpenEmbedded build
system ignores your request and will install the packages to avoid
dependency errors.

Note
Some recommended packages might be required for certain
system functionality, such as kernel modules. It is up to you
to add packages with the IMAGE_INSTALL variable.
Support for this variable exists only when using the IPK and RPM
packaging backend. Support does not exist for DEB.
See the BAD_RECOMMENDATIONS and the PACKAGE_EXCLUDE variables
for related information.
Causes the OpenEmbedded build system to skip building the .hddimg
image. The NOHDD variable is used with the bootimg class. Set the
variable to "1" to prevent the .hddimg image from being built.
NOHDD
Causes the OpenEmbedded build system to skip building the ISO
image. The NOISO variable is used with the bootimg class. Set the
variable to "1" to prevent the ISO image from being built. To enable
building an ISO image, set the variable to "0".
NOISO

O
When inheriting the binconfig class, this variable specifies
additional arguments passed to the "sed" command. The sed
command alters any paths in configuration scripts that have been
set up during compilation. Inheriting this class results in all paths in
these scripts being changed to point into the sysroots/ directory so
OE_BINCONFIG_EXTRA_MANGLE
that all builds that use the script will use the correct directories for
the cross compiling layout.
See the meta/classes/binconfig.bbclass in the Source
Directory
[http://www.yoctoproject.org/docs/1.8/dev-manual/devmanual.html#source-directory] for details on how this class applies
these additional sed command arguments. For general information
on the binconfig.bbclass class, see the "Binary Configuration
Scripts - binconfig.bbclass" section.
An internal variable used to tell the OpenEmbedded build system
what Python modules to import for every Python function run by the
system.
OE_IMPORTS

Note
Do not set this variable. It is for internal use only.

175

Variables Glossary

OE_TERMINAL

Controls how the OpenEmbedded build system spawns
interactive terminals on the host development system (e.g.
using the BitBake command with the -c
devshell
command-line option). For more information, see the "Using
a Development Shell [http://www.yoctoproject.org/docs/1.8/devmanual/dev-manual.html#platdev-appdev-devshell]" section in the
Yocto Project Development Manual.
You can use the following values for the OE_TERMINAL variable:
auto
gnome
xfce
rxvt
screen
konsole
none

Note
Konsole support only works for KDE 3.x. Also, "auto" is the
default behavior for OE_TERMINAL

OEROOT

The directory from which the top-level build environment setup script
is sourced. The Yocto Project makes two top-level build environment
setup scripts available: oe-init-build-env and oe-init-buildenv-memres. When you run one of these scripts, the OEROOT variable
resolves to the directory that contains the script.
For additional information on how this variable is used, see the
initialization scripts.
Declares the oldest version of the Linux kernel that the produced
binaries must support. This variable is passed into the build of the
Embedded GNU C Library (eglibc).

The default for this variable comes from the meta/conf/
OLDEST_KERNEL bitbake.conf configuration file. You can override this default by
setting the variable in a custom distribution configuration file.

OVERRIDES

BitBake uses OVERRIDES to control what variables are overridden
after BitBake parses recipes and configuration files. You can find more
information on how overrides are handled in the "Conditional Syntax
(Overrides)
[http://www.yoctoproject.org/docs/1.8/bitbake-usermanual/bitbake-user-manual.html#conditional-syntax-overrides]"
section of the BitBake User Manual.

P
The recipe name and version. P is comprised of the following:
${PN}-${PV}
P
The architecture of the resulting package or packages.

PACKAGE_ARCH

By default, the value of this variable is set to TUNE_PKGARCH when
building for the target, BUILD_ARCH when building for the build
host and "${SDK_ARCH}-${SDKPKGSUFFIX}" when building for the
SDK. However, if your recipe's output packages are built specific to
the target machine rather than general for the architecture of the
machine, you should set PACKAGE_ARCH to the value of MACHINE_ARCH
in the recipe as follows:

176

Variables Glossary

PACKAGE_ARCH = "${MACHINE_ARCH}"

PACKAGE_ARCHS

Specifies a list of architectures compatible with the target machine.
This variable is set automatically and should not normally be handedited. Entries are separated using spaces and listed in order of
priority. The default value for PACKAGE_ARCHS is "all any noarch
${PACKAGE_EXTRA_ARCHS} ${MACHINE_ARCH}".
Enables easily adding packages to PACKAGES before ${PN} so that
those added packages can pick up files that would normally be
included in the default package.

PACKAGE_BEFORE_PN
This variable, which is set in the local.conf configuration file found
in the conf folder of the Build Directory [http://www.yoctoproject.org/
docs/1.8/dev-manual/dev-manual.html#build-directory],
specifies
the package manager the OpenEmbedded build system uses when
packaging data.
PACKAGE_CLASSES
You can provide one or more of the following arguments for the
variable:

PACKAGE_CLASSES ?= "package_rpm package_deb package_ipk package_ta
The build system uses only the first argument in the list as the
package manager when creating your image or SDK. However,
packages will be created using any additional packaging classes you
specify. For example, if you use the following in your local.conf file:
PACKAGE_CLASSES ?= "package_ipk package_tar"
The OpenEmbedded build system uses the IPK package manager to
create your image or SDK as well as generating TAR packages.
You cannot specify the package_tar class first in the list. Files using
the .tar format cannot be used as a substitute packaging format for
DEB, RPM, and IPK formatted files for your image or SDK.
For information on packaging and build performance effects as a
result of the package manager in use, see the "package.bbclass"
section.
Determines how to split up the binary and debug information when
creating *-dbg packages to be used with the GNU Project Debugger
(GDB).
With the PACKAGE_DEBUG_SPLIT_STYLE variable, you can control
PACKAGE_DEBUG_SPLIT_STYLE
where debug information, which can include or exclude source files,
is stored:
• ".debug": Debug symbol files are placed next to the binary in a
.debug directory on the target. For example, if a binary is installed
into /bin, the corresponding debug symbol files are installed in /
bin/.debug. Source files are placed in /usr/src/debug. This is the
default behavior.
• "debug-file-directory": Debug symbol files are placed under /usr/
lib/debug on the target, and separated by the path from where

177

Variables Glossary

the binary is installed. For example, if a binary is installed in /
bin, the corresponding debug symbols are installed in /usr/lib/
debug/bin. Source files are placed in /usr/src/debug.
• "debug-without-src": The same behavior as ".debug" previously
described with the exception that no source files are installed.
You can find out more about debugging using GDB by
reading the "Debugging With the GNU Project Debugger
(GDB) Remotely [http://www.yoctoproject.org/docs/1.8/dev-manual/
dev-manual.html#platdev-gdb-remotedebug]" section in the Yocto
Project Development Manual.
Lists packages that should not be installed into an image. For
example:

PACKAGE_EXCLUDE

PACKAGE_EXCLUDE = "package_name package_name package_name ..."

You can set this variable globally in your local.conf file or you can
attach it to a specific image recipe by using the recipe name override:
PACKAGE_EXCLUDE_pn-target_image = "package_name"
If you choose to not install a package using this variable and
some other package is dependent on it (i.e. listed in a recipe's
RDEPENDS variable), the OpenEmbedded build system generates a
fatal installation error. Because the build system halts the process
with a fatal error, you can use the variable with an iterative
development process to remove specific components from a system.
Support for this variable exists only when using the IPK and RPM
packaging backend. Support does not exist for DEB.
See the NO_RECOMMENDATIONS and the BAD_RECOMMENDATIONS
variables for related information.
Specifies the list of architectures compatible with the device CPU.
This variable is useful when you build for several different devices
that use miscellaneous processors such as XScale and ARM926-EJS.
PACKAGE_EXTRA_ARCHS
The
PACKAGE_GROUP
variable
FEATURE_PACKAGES.
See
the
FEATURE_PACKAGES for information.
PACKAGE_GROUP

has
been
renamed
variable
description

to
for

If if you use the PACKAGE_GROUP variable, the OpenEmbedded build
system issues a warning message.
The final list of packages passed to the package manager for
installation into the image.

Because the package manager controls actual installation of all
packages, the list of packages passed using PACKAGE_INSTALL is not
PACKAGE_INSTALL
the final list of packages that are actually installed. This variable is
internal to the image construction code. Consequently, in general,
you should use the IMAGE_INSTALL variable to specify packages
for installation. The exception to this is when working with the
core-image-minimal-initramfs [119] image. When working with
an initial RAM disk (initramfs) image, use the PACKAGE_INSTALL
variable.
178

Variables Glossary

Specifies a list of functions run to pre-process the PKGD directory prior
to splitting the files out to individual packages.

PACKAGE_PREPROCESS_FUNCS
This variable provides a means of enabling or disabling features of
a recipe on a per-recipe basis. PACKAGECONFIG blocks are defined in
recipes when you specify features and then arguments that define
feature behaviors. Here is the basic block structure:
PACKAGECONFIG
PACKAGECONFIG ??=
PACKAGECONFIG[f1]
PACKAGECONFIG[f2]
PACKAGECONFIG[f3]

"f1 f2 f3 ..."
= "--with-f1,--without-f1,build-deps-f1,rt-deps= "--with-f2,--without-f2,build-deps-f2,rt-deps= "--with-f3,--without-f3,build-deps-f3,rt-deps-

The PACKAGECONFIG variable itself specifies a space-separated list of
the features to enable. Following the features, you can determine
the behavior of each feature by providing up to four order-dependent
arguments, which are separated by commas. You can omit any
argument you like but must retain the separating commas. The order
is important and specifies the following:
1. Extra arguments that should be added to the configure script
argument list (EXTRA_OECONF) if the feature is enabled.
2. Extra arguments that should be added to EXTRA_OECONF if the
feature is disabled.
3. Additional build dependencies (DEPENDS) that should be added if
the feature is enabled.
4. Additional runtime dependencies (RDEPENDS) that should be added
if the feature is enabled.
Consider the following PACKAGECONFIG block taken from the librsvg
recipe. In this example the feature is croco, which has three
arguments that determine the feature's behavior.
PACKAGECONFIG ??= "croco"
PACKAGECONFIG[croco] = "--with-croco,--without-croco,libcroco"
The --with-croco and libcroco arguments apply only if the feature
is enabled. In this case, --with-croco is added to the configure script
argument list and libcroco is added to DEPENDS. On the other hand,
if the feature is disabled say through a .bbappend file in another
layer, then the second argument --without-croco is added to the
configure script rather than --with-croco.
The basic PACKAGECONFIG structure previously described holds true
regardless of whether you are creating a block or changing a block.
When creating a block, use the structure inside your recipe.
If you want to change an existing PACKAGECONFIG block, you can do
so one of two ways:
• Append file: Create an append file named recipename.bbappend
in your layer and override the value of PACKAGECONFIG. You can
either completely override the variable:
PACKAGECONFIG="f4 f5"
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Variables Glossary

Or, you can just append the variable:
PACKAGECONFIG_append = " f4"
• Configuration file: This method is identical to changing the block
through an append file except you edit your local.conf or
mydistro.conf file. As with append files previously described, you
can either completely override the variable:
PACKAGECONFIG_pn-recipename="f4 f5"
Or, you can just amend the variable:
PACKAGECONFIG_append_pn-recipename = " f4"
The list of packages to be created from the recipe. The default value
is the following:

PACKAGES

${PN}-dbg ${PN}-staticdev ${PN}-dev ${PN}-doc ${PN}-locale ${PACKA

A promise that your recipe satisfies runtime dependencies for
optional modules that are found in other recipes. PACKAGES_DYNAMIC
does not actually satisfy the dependencies, it only states that they
should be satisfied. For example, if a hard, runtime dependency
(RDEPENDS) of another package is satisfied at build time through the
PACKAGES_DYNAMIC
PACKAGES_DYNAMIC variable, but a package with the module name is
never actually produced, then the other package will be broken. Thus,
if you attempt to include that package in an image, you will get a
dependency failure from the packaging system during the do_rootfs
task.
Typically, if there is a chance that such a situation can occur and
the package that is not created is valid without the dependency
being satisfied, then you should use RRECOMMENDS (a soft runtime
dependency) instead of RDEPENDS.
For an example of how to use the PACKAGES_DYNAMIC variable
when you are splitting packages, see the "Handling Optional Module
Packaging [http://www.yoctoproject.org/docs/1.8/dev-manual/devmanual.html#handling-optional-module-packaging]" section in the
Yocto Project Development Manual.
Specifies a list of functions run to perform additional splitting of
files into individual packages. Recipes can either prepend to this
variable or prepend to the populate_packages function in order
to perform additional package splitting. In either case, the function
should set PACKAGES, FILES, RDEPENDS and other packaging variables
PACKAGESPLITFUNCS
appropriately in order to perform the desired splitting.
Extra options passed to the make command during the do_compile
task in order to specify parallel compilation on the local build host.
This variable is usually in the form "-j ", where x represents the
maximum number of parallel threads make can run.
PARALLEL_MAKE

If your development host supports multiple cores, a good rule of
thumb is to set this variable to twice the number of cores on the host.
180

Variables Glossary

If you do not set PARALLEL_MAKE, it defaults to the number of cores
your build system has.

Note
Individual recipes might clear out this variable if the software
being built has problems running its make process in parallel.
Extra options passed to the make install command during the
do_install task in order to specify parallel installation. This variable
defaults to the value of PARALLEL_MAKE.
PARALLEL_MAKEINST

Note
Individual recipes might clear out this variable if the software
being built has problems running its make install process
in parallel.

Determines the action to take when a patch fails. You can set this
variable to one of two values: "noop" and "user".

PATCHRESOLVE

The default value of "noop" causes the build to simply fail when
the OpenEmbedded build system cannot successfully apply a patch.
Setting the value to "user" causes the build system to launch a shell
and places you in the right location so that you can manually resolve
the conflicts.
Set this variable in your local.conf file.

PATCHTOOL

Specifies the utility used to apply patches for a recipe during the
do_patch task. You can specify one of three utilities: "patch", "quilt",
or "git". The default utility used is "quilt" except for the quilt-native
recipe itself. Because the quilt tool is not available at the time quiltnative is being patched, it uses "patch".
If you wish to use an alternative patching tool, set the variable in the
recipe using one of the following:
PATCHTOOL = "patch"
PATCHTOOL = "quilt"
PATCHTOOL = "git"
The epoch of the recipe. By default, this variable is unset. The
variable is used to make upgrades possible when the versioning
scheme changes in some backwards incompatible way.

PE
Specifies the recipe or package name and includes all version
and revision numbers (i.e. eglibc-2.13-r20+svnr15508/ and
bash-4.2-r1/). This variable is comprised of the following:
PF

${PN}-${EXTENDPE}${PV}-${PR}

When inheriting the pixbufcache class, this variable identifies
packages that contain the pixbuf loaders used with gdk-pixbuf. By
default, the pixbufcache class assumes that the loaders are in the
recipe's main package (i.e. ${PN}). Use this variable if the loaders
you need are in a package other than that main package.
PIXBUF_PACKAGES

181

Variables Glossary

The name of the resulting package created by the OpenEmbedded
build system.

Note
PKG

When using the PKG variable, you must use a package name
override.
For example, when the debian class renames the output package, it
does so by setting PKG_packagename.
Points to the destination directory for files to be packaged before
they are split into individual packages. This directory defaults to the
following:

PKGD

${WORKDIR}/package
Do not change this default.

PKGDATA_DIR

Points to a shared, global-state directory that holds data generated
during the packaging process. During the packaging process, the
do_packagedata task packages data for each recipe and installs
it into this temporary, shared area. This directory defaults to the
following:
${STAGING_DIR_HOST}/pkgdata
Do not change this default.
Points to the parent directory for files to be packaged after they have
been split into individual packages. This directory defaults to the
following:

PKGDEST

${WORKDIR}/packages-split
Under this directory, the build system creates directories for each
package specified in PACKAGES. Do not change this default.
Points to a temporary work area used by the do_package task to write
output from the do_packagedata task. The PKGDESTWORK location
defaults to the following:

PKGDESTWORK

${WORKDIR}/pkgdata
The do_packagedata task then packages the data in the temporary
work area and installs it into a shared directory pointed to by
PKGDATA_DIR.
Do not change this default.
The epoch of the output package built by the OpenEmbedded build
system. By default, PKGE is set to PE.

PKGE

182

Variables Glossary

The revision of the output package built by the OpenEmbedded build
system. By default, PKGR is set to PR.

PKGR
The version of the output package built by the OpenEmbedded build
system. By default, PKGV is set to PV.

PKGV
This variable can have two separate functions depending on the
context: a recipe name or a resulting package name.

PN

PN refers to a recipe name in the context of a file used by the
OpenEmbedded build system as input to create a package. The name
is normally extracted from the recipe file name. For example, if the
recipe is named expat_2.0.1.bb, then the default value of PN will
be "expat".
The variable refers to a package name in the context of a file created
or produced by the OpenEmbedded build system.
If applicable, the PN variable also contains any special suffix or prefix.
For example, using bash to build packages for the native machine,
PN is bash-native. Using bash to build packages for the target and
for Multilib, PN would be bash and lib64-bash, respectively.
Lists recipes you do not want the OpenEmbedded build system to
build. This variable works in conjunction with the blacklist class,
which the recipe must inherit globally.

PNBLACKLIST

To prevent a recipe from being built, inherit the class globally and
use the variable in your local.conf file. Here is an example that
prevents myrecipe from being built:
INHERIT += "blacklist"
PNBLACKLIST[myrecipe] = "Not supported by our organization."
The revision of the recipe. The default value for this variable is "r0".

PR
If multiple recipes provide an item, this variable determines which
recipe should be given preference. You should always suffix the
variable with the name of the provided item, and you should set it
to the PN of the recipe to which you want to give precedence. Some
examples:
PREFERRED_PROVIDER
PREFERRED_PROVIDER_virtual/kernel ?= "linux-yocto"
PREFERRED_PROVIDER_virtual/xserver = "xserver-xf86"
PREFERRED_PROVIDER_virtual/libgl ?= "mesa"
If there are multiple versions of recipes available, this variable
determines which recipe should be given preference. You must

PREFERRED_VERSION

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Variables Glossary

always suffix the variable with the PN you want to select, and you
should set the PV accordingly for precedence. You can use the "%"
character as a wildcard to match any number of characters, which
can be useful when specifying versions that contain long revision
numbers that could potentially change. Here are two examples:
PREFERRED_VERSION_python = "2.7.3"
PREFERRED_VERSION_linux-yocto = "3.10%"

PREMIRRORS

Specifies additional paths from which the OpenEmbedded build
system gets source code. When the build system searches for source
code, it first tries the local download directory. If that location fails,
the build system tries locations defined by PREMIRRORS, the upstream
source, and then locations specified by MIRRORS in that order.
Assuming your distribution (DISTRO) is "poky", the default value for
PREMIRRORS is defined in the conf/distro/poky.conf file in the
meta-yocto Git repository.
Typically, you could add a specific server for the build
system to attempt before any others by adding something
like the following to the local.conf configuration file in the
Build Directory [http://www.yoctoproject.org/docs/1.8/dev-manual/
dev-manual.html#build-directory]:
PREMIRRORS_prepend = "\
git://.*/.* http://www.yoctoproject.org/sources/ \n \
ftp://.*/.* http://www.yoctoproject.org/sources/ \n \
http://.*/.* http://www.yoctoproject.org/sources/ \n \
https://.*/.* http://www.yoctoproject.org/sources/ \n"
These changes cause the build system to intercept Git, FTP, HTTP,
and HTTPS requests and direct them to the http:// sources mirror.
You can use file:// URLs to point to local directories or network
shares as well.

PRINC

PRIVATE_LIBS

The PRINC variable has been deprecated and triggers a warning
if detected during a build. For PR increments on changes, use the
PR service instead. You can find out more about this service in the
"Working With a PR Service [http://www.yoctoproject.org/docs/1.8/
dev-manual/dev-manual.html#working-with-a-pr-service]" section in
the Yocto Project Development Manual.
Specifies libraries installed within a recipe that should be ignored
by the OpenEmbedded build system's shared library resolver. This
variable is typically used when software being built by a recipe has its
own private versions of a library normally provided by another recipe.
In this case, you would not want the package containing the private
libraries to be set as a dependency on other unrelated packages
that should instead depend on the package providing the standard
version of the library.
Libraries specified in this variable should be specified by their file
name. For example, from the Firefox recipe in meta-browser:
PRIVATE_LIBS = "libmozjs.so \
libxpcom.so \
libnspr4.so \
libxul.so \
libmozalloc.so \
libplc4.so \
184

Variables Glossary

libplds4.so"

PROVIDES

A list of aliases by which a particular recipe can be known. By default,
a recipe's own PN is implicitly already in its PROVIDES list. If a recipe
uses PROVIDES, the additional aliases are synonyms for the recipe
and can be useful satisfying dependencies of other recipes during
the build as specified by DEPENDS.
Consider the following example PROVIDES statement from a recipe
file libav_0.8.11.bb:
PROVIDES += "libpostproc"
The PROVIDES statement results in the "libav" recipe also being
known as "libpostproc".
The network based PR service host and port.

PRSERV_HOST

The conf/local.conf.sample.extended configuration file in the
Source Directory [http://www.yoctoproject.org/docs/1.8/dev-manual/
dev-manual.html#source-directory] shows how the PRSERV_HOST
variable is set:
PRSERV_HOST = "localhost:0"
You must set the variable if you want to automatically start a local
PR service [http://www.yoctoproject.org/docs/1.8/dev-manual/devmanual.html#working-with-a-pr-service]. You can set PRSERV_HOST
to other values to use a remote PR service.

Specifies whether or not Package Test [http://www.yoctoproject.org/
docs/1.8/dev-manual/dev-manual.html#testing-packages-withptest] (ptest) functionality is enabled when building a recipe. You
should not set this variable directly. Enabling and disabling building
Package Tests at build time should be done by adding "ptest" to (or
PTEST_ENABLED
removing it from) DISTRO_FEATURES.

PV

PYTHON_ABI

The version of the recipe. The version is normally extracted
from the recipe filename. For example, if the recipe is named
expat_2.0.1.bb, then the default value of PV will be "2.0.1". PV
is generally not overridden within a recipe unless it is building an
unstable (i.e. development) version from a source code repository
(e.g. Git or Subversion).
When used by recipes that inherit the distutils3, setuptools3,
distutils, or setuptools classes, denotes the Application Binary
Interface (ABI) currently in use for Python. By default, the ABI is "m".
You do not have to set this variable as the OpenEmbedded build
system sets it for you.
The OpenEmbedded build system uses the ABI to construct directory
names used when installing the Python headers and libraries in
sysroot (e.g. .../python3.3m/...).
Recipes that inherit the distutils class during cross-builds also use
this variable to locate the headers and libraries of the appropriate
Python that the extension is targeting.

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Variables Glossary

PYTHON_PN

When used by recipes that inherit the distutils3, setuptools3,
distutils, or setuptools classes, specifies the major Python
version being built. For Python 2.x, PYTHON_PN would be "python2".
For Python 3.x, the variable would be "python3". You do not have to
set this variable as the OpenEmbedded build system automatically
sets it for you.
The variable allows recipes to use common infrastructure such as the
following:
DEPENDS += "${PYTHON_PN}-native"
In the previous example, the version of the dependency is
PYTHON_PN.

Q
Specifies your own subset of .pro files to be built for use with qmake.
If you do not set this variable, all .pro files in the directory pointed
to by S will be built by default.
QMAKE_PROFILES

This variable is used with recipes that inherit the qmake_base class
or other classes that inherit qmake_base.

R
The list of packages that conflict with packages. Note that packages
will not be installed if conflicting packages are not first removed.

RCONFLICTS

Like all package-controlling variables, you must always use them in
conjunction with a package name override. Here is an example:
RCONFLICTS_${PN} = "another-conflicting-package-name"
BitBake, which the OpenEmbedded build system uses, supports
specifying versioned dependencies. Although the syntax varies
depending on the packaging format, BitBake hides these differences
from you. Here is the general syntax to specify versions with the
RCONFLICTS variable:
RCONFLICTS_${PN} = "package (operator version)"
For operator, you can specify the following:
=
<
>
<=
>=
For example, the following sets up a dependency on version 1.2 or
greater of the package foo:
RCONFLICTS_${PN} = "foo (>= 1.2)"
186

Variables Glossary

Lists a package's runtime dependencies (i.e. other packages) that
must be installed in order for the built package to run correctly. If a
package in this list cannot be found during the build, you will get a
build error.
RDEPENDS

When you use the RDEPENDS variable in a recipe, you are essentially
stating that the recipe's do_build task depends on the existence
of a specific package. Consider this simple example for two recipes
named "a" and "b" that produce similarly named IPK packages. In
this example, the RDEPENDS statement appears in the "a" recipe:
RDEPENDS_${PN} = "b"
Here, the dependency is such that the do_build task for recipe
"a" depends on the do_package_write_ipk task of recipe "b". This
means the package file for "b" must be available when the output
for recipe "a" has been completely built. More importantly, package
"a" will be marked as depending on package "b" in a manner that is
understood by the package manager.
The names of the packages you list within RDEPENDS must be the
names of other packages - they cannot be recipe names. Although
package names and recipe names usually match, the important point
here is that you are providing package names within the RDEPENDS
variable. For an example of the default list of packages created from
a recipe, see the PACKAGES variable.
Because the RDEPENDS variable applies to packages being built, you
should always use the variable in a form with an attached package
name. For example, suppose you are building a development
package that depends on the perl package. In this case, you would
use the following RDEPENDS statement:
RDEPENDS_${PN}-dev += "perl"
In the example, the development package depends on the perl
package. Thus, the RDEPENDS variable has the ${PN}-dev package
name as part of the variable.
The package name you attach to the RDEPENDS variable must appear
as it would in the PACKAGES namespace before any renaming of the
output package by classes like debian.
In many cases you do not need to explicitly add runtime
dependencies using RDEPENDS since some automatic handling
occurs:
• shlibdeps: If a runtime package contains a shared library (.so),
the build processes the library in order to determine other libraries
to which it is dynamically linked. The build process adds these
libraries to RDEPENDS when creating the runtime package.
• pcdeps: If the package ships a pkg-config information file, the
build process uses this file to add items to the RDEPENDS variable
to create the runtime packages.
BitBake, which the OpenEmbedded build system uses, supports
specifying versioned dependencies. Although the syntax varies
depending on the packaging format, BitBake hides these differences
from you. Here is the general syntax to specify versions with the
RDEPENDS variable:
187

Variables Glossary

RDEPENDS_${PN} = "package (operator version)"
For operator, you can specify the following:
=
<
>
<=
>=
For example, the following sets up a dependency on version 1.2 or
greater of the package foo:
RDEPENDS_${PN} = "foo (>= 1.2)"
For information on build-time dependencies, see the DEPENDS
variable.
When inheriting the distro_features_check class, this variable
identifies distribution features that must exist in the current
configuration in order for the OpenEmbedded build system to
build the recipe. In other words, if the REQUIRED_DISTRO_FEATURES
variable lists a feature that does not appear in DISTRO_FEATURES
REQUIRED_DISTRO_FEATURES
within the current configuration, an error occurs and the build stops.
Reclaims disk space by removing previously built versions of the
same image from the images directory pointed to by the DEPLOY_DIR
variable.
RM_OLD_IMAGE

Set this variable to "1" in your local.conf file to remove these
images.
With rm_work enabled, this variable specifies a list of recipes whose
work directories should not be removed. See the "rm_work.bbclass"
section for more details.

RM_WORK_EXCLUDE
Defines the root home directory. By default, this directory is set as
follows in the BitBake configuration file:

ROOT_HOME

ROOT_HOME ??= "/home/root"

Note
This default value is likely used because some embedded
solutions prefer to have a read-only root filesystem and
prefer to keep writeable data in one place.
You can override the default by setting the variable in any layer or
in the local.conf file. Because the default is set using a "weak"
assignment (i.e. "??="), you can use either of the following forms to
define your override:
ROOT_HOME = "/root"
ROOT_HOME ?= "/root"

188

Variables Glossary

These override examples use /root, which is probably the most
commonly used override.
Indicates a filesystem image to include as the root filesystem.
The ROOTFS variable is an optional variable used with the bootimg
class.
ROOTFS
Added by classes to run post processing commands once the
OpenEmbedded build system has created the root filesystem. You
can specify shell commands separated by semicolons:
ROOTFS_POSTPROCESS_COMMAND
ROOTFS_POSTPROCESS_COMMAND += "shell_command; ... "
If you need to pass the path to the root filesystem within the
command, you can use ${IMAGE_ROOTFS}, which points to the
root filesystem image. See the IMAGE_ROOTFS variable for more
information.
A list of package name aliases that a package also provides. These
aliases are useful for satisfying runtime dependencies of other
packages both during the build and on the target (as specified by
RDEPENDS).
RPROVIDES

Note
A package's own name is implicitly already in its RPROVIDES
list.
As with all package-controlling variables, you must always use the
variable in conjunction with a package name override. Here is an
example:
RPROVIDES_${PN} = "widget-abi-2"

RRECOMMENDS

A list of packages that extends the usability of a package being built.
The package being built does not depend on this list of packages
in order to successfully build, but rather uses them for extended
usability. To specify runtime dependencies for packages, see the
RDEPENDS variable.
The package manager will automatically install the RRECOMMENDS
list of packages when installing the built package. However,
you can prevent listed packages from being installed by
using the BAD_RECOMMENDATIONS, NO_RECOMMENDATIONS, and
PACKAGE_EXCLUDE variables.
Packages specified in RRECOMMENDS need not actually be produced.
However, a recipe must exist that provides each package, either
through the PACKAGES or PACKAGES_DYNAMIC variables or the
RPROVIDES variable, or an error will occur during the build. If such
a recipe does exist and the package is not produced, the build
continues without error.
Because the RRECOMMENDS variable applies to packages being built,
you should always attach an override to the variable to specify the
particular package whose usability is being extended. For example,
suppose you are building a development package that is extended
to support wireless functionality. In this case, you would use the
following:
189

Variables Glossary

RRECOMMENDS_${PN}-dev += "wireless_package_name"
In the example, the package name (${PN}-dev) must appear as it
would in the PACKAGES namespace before any renaming of the output
package by classes such as debian.bbclass.
BitBake, which the OpenEmbedded build system uses, supports
specifying versioned recommends. Although the syntax varies
depending on the packaging format, BitBake hides these differences
from you. Here is the general syntax to specify versions with the
RRECOMMENDS variable:
RRECOMMENDS_${PN} = "package (operator version)"
For operator, you can specify the following:
=
<
>
<=
>=
For example, the following sets up a recommend on version 1.2 or
greater of the package foo:
RRECOMMENDS_${PN} = "foo (>= 1.2)"

RREPLACES

A list of packages replaced by a package. The package manager
uses this variable to determine which package should be installed to
replace other package(s) during an upgrade. In order to also have
the other package(s) removed at the same time, you must add the
name of the other package to the RCONFLICTS variable.
As with all package-controlling variables, you must use this variable
in conjunction with a package name override. Here is an example:
RREPLACES_${PN} = "other-package-being-replaced"
BitBake, which the OpenEmbedded build system uses, supports
specifying versioned replacements. Although the syntax varies
depending on the packaging format, BitBake hides these differences
from you. Here is the general syntax to specify versions with the
RREPLACES variable:
RREPLACES_${PN} = "package (operator version)"
For operator, you can specify the following:
=
<
>
<=
>=
190

Variables Glossary

For example, the following sets up a replacement using version 1.2
or greater of the package foo:
RREPLACES_${PN} = "foo (>= 1.2)"
A list of additional packages that you can suggest for installation
by the package manager at the time a package is installed. Not all
package managers support this functionality.
RSUGGESTS

As with all package-controlling variables, you must always use this
variable in conjunction with a package name override. Here is an
example:
RSUGGESTS_${PN} = "useful-package another-package"

S

S

The location in the Build Directory [http://www.yoctoproject.org/
docs/1.8/dev-manual/dev-manual.html#build-directory]
where
unpacked recipe source code resides. This location is within the work
directory (WORKDIR), which is not static. The unpacked source location
depends on the recipe name (PN) and recipe version (PV) as follows:
${WORKDIR}/${PN}-${PV}
As
an
example,
assume
a
Source
Directory
[http://
www.yoctoproject.org/docs/1.8/dev-manual/devmanual.html#source-directory] top-level folder named poky and a
default Build Directory at poky/build. In this case, the work directory
the build system uses to keep the unpacked recipe for db is the
following:
poky/build/tmp/work/qemux86-poky-linux/db/5.1.19-r3/db-5.1.19
Specifies a list of command-line utilities that should be checked for
during the initial sanity checking process when running BitBake. If
any of the utilities are not installed on the build host, then BitBake
immediately exits with an error.

SANITY_REQUIRED_UTILITIES
A list of the host distribution identifiers that the build system has
been tested against. Identifiers consist of the host distributor ID
followed by the release, as reported by the lsb_release tool or as
read from /etc/lsb-release. Separate the list items with explicit
newline characters (\n). If SANITY_TESTED_DISTROS is not empty and
SANITY_TESTED_DISTROS
the current value of NATIVELSBSTRING does not appear in the list,
then the build system reports a warning that indicates the current
host distribution has not been tested as a build host.
The target architecture for the SDK. Typically, you do not directly set
this variable. Instead, use SDKMACHINE.

SDK_ARCH
191

Variables Glossary

The directory set up and used by the populate_sdk_base to
which the SDK is deployed. The populate_sdk_base class defines
SDK_DEPLOY as follows:
SDK_DEPLOY

SDK_DEPLOY = "${TMPDIR}/deploy/sdk"
The parent directory used by the OpenEmbedded build system when
creating SDK output. The populate_sdk_base class defines the
variable as follows:

SDK_DIR

SDK_DIR = "${WORKDIR}/sdk"

Note
The SDK_DIR directory is a temporary directory as it is part
of WORKDIR. The final output directory is SDK_DEPLOY.
The base name for SDK output files. The name is derived from
the DISTRO, TCLIBC, SDK_ARCH, IMAGE_BASENAME, and TUNE_PKGARCH
variables:
SDK_NAME

SDK_NAME = "${DISTRO}-${TCLIBC}-${SDK_ARCH}-${IMAGE_BASENAME}-${TU
The location used by the OpenEmbedded build system when creating
SDK output. The populate_sdk_base class defines the variable as
follows:

SDK_OUTPUT

SDK_OUTPUT = "${SDK_DIR}/image"

Note
The SDK_OUTPUT directory is a temporary directory as it is
part of WORKDIR by way of SDK_DIR. The final output directory
is SDK_DEPLOY.
Specifies a list of architectures compatible with the SDK machine.
This variable is set automatically and should not normally be handedited. Entries are separated using spaces and listed in order of
priority. The default value for SDK_PACKAGE_ARCHS is "all any noarch
${SDK_ARCH}-${SDKPKGSUFFIX}".
SDK_PACKAGE_ARCHS
Equivalent to IMAGE_FEATURES. However, this variable applies to the
SDK generated from an image using the following command:

SDKIMAGE_FEATURES

$ bitbake -c populate_sdk imagename

The machine for which the Application Development Toolkit (ADT) or
SDK is built. In other words, the SDK or ADT is built such that it runs on
the target you specify with the SDKMACHINE value. The value points
to a corresponding .conf file under conf/machine-sdk/.
SDKMACHINE

You can use "i686" and "x86_64" as possible values for this variable.
The variable defaults to "i686" and is set in the local.conf file in the
Build Directory.
SDKMACHINE ?= "i686"

192

Variables Glossary

Note
You cannot set the SDKMACHINE variable in your distribution
configuration file. If you do, the configuration will not take
affect.

SDKPATH

Defines the path offered to the user for installation of the SDK that
is generated by the OpenEmbedded build system. The path appears
as the default location for installing the SDK when you run the SDK's
installation script. You can override the offered path when you run
the script.
The section in which packages should be categorized. Package
management utilities can make use of this variable.

SECTION
Specifies the optimization flags passed to the C compiler when
building for the target. The flags are passed through the default value
of the TARGET_CFLAGS variable.
The SELECTED_OPTIMIZATION variable takes the value of
SELECTED_OPTIMIZATION
FULL_OPTIMIZATION unless DEBUG_BUILD = "1". If that is the case,
the value of DEBUG_OPTIMIZATION is used.
Defines a serial console (TTY) to enable using getty. Provide a
value that specifies the baud rate followed by the TTY device name
separated by a space. You cannot specify more than one TTY device:
SERIAL_CONSOLE

SERIAL_CONSOLE = "115200 ttyS0"

Note
The SERIAL_CONSOLE variable is deprecated. Please use the
SERIAL_CONSOLES variable.
Defines the serial consoles (TTYs) to enable using getty. Provide a
value that specifies the baud rate followed by the TTY device name
separated by a semicolon. Use spaces to separate multiple devices:
SERIAL_CONSOLES

SERIAL_CONSOLES = "115200;ttyS0 115200;ttyS1"

Similar to SERIAL_CONSOLES except the device is checked for
existence before attempting to enable it. This variable is currently
only supported with SysVinit (i.e. not with systemd).
SERIAL_CONSOLES_CHECK
A list of recipe dependencies that should not be used to determine
signatures of tasks from one recipe when they depend on tasks from
another recipe. For example:
SIGGEN_EXCLUDE_SAFE_RECIPE_DEPS
SIGGEN_EXCLUDE_SAFE_RECIPE_DEPS += "intone->mplayer2"
In this example, intone depends on mplayer2.
Use of this variable is one mechanism to remove dependencies that
affect task signatures and thus force rebuilds when a recipe changes.

193

Variables Glossary

Caution
If you add an inappropriate dependency for a recipe
relationship, the software might break during runtime if the
interface of the second recipe was changed after the first
recipe had been built.
A list of recipes that are completely stable and will never change. The
ABI for the recipes in the list are presented by output from the tasks
run to build the recipe. Use of this variable is one way to remove
dependencies from one recipe on another that affect task signatures
and thus force rebuilds when the recipe changes.
SIGGEN_EXCLUDERECIPES_ABISAFE

Caution
If you add an inappropriate variable to this list, the software
might break at runtime if the interface of the recipe was
changed after the other had been built.
Specifies the number of bits for the target system CPU. The value
should be either "32" or "64".

SITEINFO_BITS
Specifies the endian byte order of the target system. The value
should be either "le" for little-endian or "be" for big-endian.

SITEINFO_ENDIANNESS
Groups together machines based upon the same family of SOC
(System On Chip). You typically set this variable in a common .inc
file that you include in the configuration files of all the machines.
SOC_FAMILY

Note
You must include conf/machine/include/soc-family.inc
for this variable to appear in MACHINEOVERRIDES.
Defines the suffix for shared libraries used on the target platform. By
default, this suffix is ".so.*" for all Linux-based systems and is defined
in the meta/conf/bitbake.conf configuration file.

SOLIBS

You will see this variable referenced in the default values of FILES_
${PN}.
Defines the suffix for the development symbolic link (symlink) for
shared libraries on the target platform. By default, this suffix is
".so" for Linux-based systems and is defined in the meta/conf/
bitbake.conf configuration file.

SOLIBSDEV

You will see this variable referenced in the default values of FILES_
${PN}-dev.
Defines your own PREMIRRORS from which to first fetch source before
attempting to fetch from the upstream specified in SRC_URI.

To use this variable, you must globally inherit the own-mirrors class
and then provide the URL to your mirrors. Here is an example:
SOURCE_MIRROR_URL
INHERIT += "own-mirrors"
SOURCE_MIRROR_URL = "http://example.com/my-source-mirror"

194

Variables Glossary

Note
You can specify only a single URL in SOURCE_MIRROR_URL.
Maps commonly used license names to their SPDX counterparts
found in meta/files/common-licenses/. For the default
SPDXLICENSEMAP mappings, see the meta/conf/licenses.conf file.
For additional information, see the LICENSE variable.
SPDXLICENSEMAP
A list of prefixes for PN used by the OpenEmbedded build system to
create variants of recipes or packages. The list specifies the prefixes
to strip off during certain circumstances such as the generation of
the BPN variable.
SPECIAL_PKGSUFFIX

SRC_URI

The list of source files - local or remote. This variable tells the
OpenEmbedded build system which bits to pull in for the build and
how to pull them in. For example, if the recipe or append file only
needs to fetch a tarball from the Internet, the recipe or append file
uses a single SRC_URI entry. On the other hand, if the recipe or
append file needs to fetch a tarball, apply two patches, and include
a custom file, the recipe or append file would include four instances
of the variable.
The following list explains the available URI protocols:
• file:// - Fetches files, which are usually files shipped with
the Metadata [http://www.yoctoproject.org/docs/1.8/dev-manual/
dev-manual.html#metadata], from the local machine. The path
is relative to the FILESPATH variable. Thus, the build system
searches, in order, from the following directories, which are
assumed to be a subdirectories of the directory in which the recipe
file (.bb) or append file (.bbappend) resides:
• ${BPN} - The base recipe name without any special suffix or
version numbers.
• ${BP} - ${BPN}-${PV}. The base recipe name and version but
without any special package name suffix.
• files - Files within a directory, which is named files and is also
alongside the recipe or append file.

Note
If you want the build system to pick up files specified
through a SRC_URI statement from your append file, you
need to be sure to extend the FILESPATH variable by
also using the FILESEXTRAPATHS variable from within your
append file.
• bzr:// - Fetches files from a Bazaar revision control repository.
• git:// - Fetches files from a Git revision control repository.
• osc:// - Fetches files from an OSC (OpenSUSE Build service)
revision control repository.
• repo:// - Fetches files from a repo (Git) repository.
• ccrc:// - Fetches files from a ClearCase repository.
• http:// - Fetches files from the Internet using http.
• https:// - Fetches files from the Internet using https.
195

Variables Glossary

• ftp:// - Fetches files from the Internet using ftp.
• cvs:// - Fetches files from a CVS revision control repository.
• hg:// - Fetches files from a Mercurial (hg) revision control
repository.
• p4:// - Fetches files from a Perforce (p4) revision control repository.
• ssh:// - Fetches files from a secure shell.
• svn:// - Fetches files from a Subversion (svn) revision control
repository.
Standard and recipe-specific options for SRC_URI exist. Here are
standard options:
• apply - Whether to apply the patch or not. The default action is to
apply the patch.
• striplevel - Which striplevel to use when applying the patch. The
default level is 1.
• patchdir - Specifies the directory in which the patch should be
applied. The default is ${S}.
Here are options specific to recipes building code from a revision
control system:
• mindate - Apply the patch only if SRCDATE is equal to or greater
than mindate.
• maxdate - Apply the patch only if SRCDATE is not later than mindate.
• minrev - Apply the patch only if SRCREV is equal to or greater than
minrev.
• maxrev - Apply the patch only if SRCREV is not later than maxrev.
• rev - Apply the patch only if SRCREV is equal to rev.
• notrev - Apply the patch only if SRCREV is not equal to rev.
Here are some additional options worth mentioning:
• unpack - Controls whether or not to unpack the file if it is an archive.
The default action is to unpack the file.
• subdir - Places the file (or extracts its contents) into the specified
subdirectory of WORKDIR. This option is useful for unusual tarballs or
other archives that do not have their files already in a subdirectory
within the archive.
• name - Specifies a name to be used for association with SRC_URI
checksums when you have more than one file specified in SRC_URI.
• downloadfilename - Specifies the filename used when storing the
downloaded file.
By default, the OpenEmbedded build system automatically detects
whether SRC_URI contains files that are machine-specific. If so,
the build system automatically changes PACKAGE_ARCH. Setting this
variable to "0" disables this behavior.
SRC_URI_OVERRIDES_PACKAGE_ARCH

196

Variables Glossary

The date of the source code used to build the package. This variable
applies only if the source was fetched from a Source Code Manager
(SCM).
SRCDATE
Returns the version string of the current package. This string is used
to help define the value of PV.

SRCPV

The
SRCPV
variable
is
defined
in
the
meta/
conf/bitbake.conf
configuration
file
in
the
Source
Directory
[http://www.yoctoproject.org/docs/1.8/dev-manual/devmanual.html#source-directory] as follows:
SRCPV = "${@bb.fetch2.get_srcrev(d)}"
Recipes that need to define PV do so with the help of the SRCPV.
For example, the ofono recipe (ofono_git.bb) located in meta/
recipes-connectivity in the Source Directory defines PV as follows:
PV = "0.12-git${SRCPV}"

SRCREV

The revision of the source code used to build the package. This
variable applies to Subversion, Git, Mercurial and Bazaar only. Note
that if you wish to build a fixed revision and you wish to avoid
performing a query on the remote repository every time BitBake
parses your recipe, you should specify a SRCREV that is a full revision
identifier and not just a tag.
The directory for the shared state cache.

SSTATE_DIR
If set to "1", allows fetches from mirrors that are specified in
SSTATE_MIRRORS to work even when fetching from the network
has been disabled by setting BB_NO_NETWORK to "1". Using the
SSTATE_MIRROR_ALLOW_NETWORK variable is useful if you have set
SSTATE_MIRRORS to point to an internal server for your shared state
SSTATE_MIRROR_ALLOW_NETWORK
cache, but you want to disable any other fetching from the network.
Configures the OpenEmbedded build system to search other mirror
locations for prebuilt cache data objects before building out the data.
This variable works like fetcher MIRRORS and PREMIRRORS and points
to the cache locations to check for the shared objects.
SSTATE_MIRRORS

You can specify a filesystem directory or a remote URL such as HTTP
or FTP. The locations you specify need to contain the shared state
cache (sstate-cache) results from previous builds. The sstate-cache
you point to can also be from builds on other machines.
If a mirror uses the same structure as SSTATE_DIR, you need to add
"PATH" at the end as shown in the examples below. The build system
substitutes the correct path within the directory structure.
SSTATE_MIRRORS ?= "\
file://.* http://someserver.tld/share/sstate/PATH \n \
file://.* file:///some-local-dir/sstate/PATH"

197

Variables Glossary

Specifies the path to the /lib subdirectory of the sysroot directory
for the build host.

STAGING_BASE_LIBDIR_NATIVE
Specifies the path to the /lib subdirectory of the sysroot
directory for the target for which the current recipe is being built
(STAGING_DIR_HOST).
STAGING_BASELIBDIR
Specifies the path to the /usr/bin subdirectory of the sysroot
directory for the target for which the current recipe is being built
(STAGING_DIR_HOST).
STAGING_BINDIR
Specifies the path to the directory containing binary configuration
scripts. These scripts provide configuration information for other
software that wants to make use of libraries or include files provided
by the software associated with the script.
STAGING_BINDIR_CROSS

Note
This style of build configuration has been largely replaced
by pkg-config. Consequently, if pkg-config is supported by
the library to which you are linking, it is recommended you
use pkg-config instead of a provided configuration script.

Specifies the path to the /usr/bin subdirectory of the sysroot
directory for the build host.

STAGING_BINDIR_NATIVE
Specifies the path to the /usr/share subdirectory of the sysroot
directory for the target for which the current recipe is being built
(STAGING_DIR_HOST).
STAGING_DATADIR
Specifies the path to the /usr/share subdirectory of the sysroot
directory for the build host.

STAGING_DATADIR_NATIVE
Specifies the path to the top-level sysroots directory (i.e. ${TMPDIR}/
sysroots).

Note
STAGING_DIR

Recipes should never write files directly under this directory
because the OpenEmbedded build system manages the
directory automatically. Instead, files should be installed to
${D} within your recipe's do_install task and then the
OpenEmbedded build system will stage a subset of those files
into the sysroot.

198

Variables Glossary

Specifies the path to the primary sysroot directory for which the
target is being built. Depending on the type of recipe and the build
target, the recipe's value is as follows:
• For recipes building for the target machine, the value is
STAGING_DIR_HOST
"${STAGING_DIR}/${MACHINE}".
• For native recipes building for the build host, the value is empty
given the assumption that when building for the build host, the
build host's own directories should be used.
• For nativesdk recipes that Build for the SDK, the value is
"${STAGING_DIR}/${MULTIMACH_HOST_SYS}".
Specifies the path to the sysroot directory for the build host.

STAGING_DIR_NATIVE
Specifies the path to the sysroot directory for the target for which
the current recipe is being built. In most cases, this path is the
STAGING_DIR_HOST.
Some recipes build binaries that can run on the target system but
STAGING_DIR_TARGET
those binaries in turn generate code for another different system
(e.g. cross-canadian recipes). Using terminology from GNU, the
primary system is referred to as the "HOST" and the secondary,
or different, system is referred to as the "TARGET". Thus, the
binaries run on the "HOST" system and and generate binaries for the
"TARGET" system. STAGING_DIR_TARGET points to the sysroot used
for the "TARGET" system.
Specifies the path to the /etc subdirectory of the sysroot directory
for the build host.

STAGING_ETCDIR_NATIVE
Specifies the path to the /usr subdirectory of the sysroot
directory for the target for which the current recipe is being built
(STAGING_DIR_HOST).
STAGING_EXECPREFIXDIR
Specifies the path to the /usr/include subdirectory of the sysroot
directory for the target for which the current recipe being built
(STAGING_DIR_HOST).
STAGING_INCDIR
Specifies the path to the /usr/include subdirectory of the sysroot
directory for the build host.

STAGING_INCDIR_NATIVE
The directory with kernel headers that are required to build out-oftree modules.

STAGING_KERNEL_DIR
199

Variables Glossary

Specifies the path to the /usr/lib subdirectory of the sysroot
directory for the target for which the current recipe is being built
(STAGING_DIR_HOST).
STAGING_LIBDIR
Specifies the path to the /usr/lib subdirectory of the sysroot
directory for the build host.

STAGING_LIBDIR_NATIVE
Specifies the base path used to create recipe stamp files. The path to
an actual stamp file is constructed by evaluating this string and then
appending additional information. Currently, the default assignment
for STAMP as set in the meta/conf/bitbake.conf file is:
STAMP

STAMP = "${STAMPS_DIR}/${MULTIMACH_TARGET_SYS}/${PN}/${EXTENDPE}${
See STAMPS_DIR, MULTIMACH_TARGET_SYS, PN, EXTENDPE, PV, and PR
for related variable information.
Specifies the base directory in which the OpenEmbedded build
system places stamps. The default directory is ${TMPDIR}/stamps.

STAMPS_DIR
The short (72 characters or less) summary of the binary package for
packaging systems such as opkg, rpm or dpkg. By default, SUMMARY
is used to define the DESCRIPTION variable if DESCRIPTION is not set
in the recipe.
SUMMARY
Specifies the kernel boot default console. If you want to use a console
other than the default, set this variable in your recipe as follows
where "X" is the console number you want to use:
SYSLINUX_DEFAULT_CONSOLE
SYSLINUX_DEFAULT_CONSOLE = "console=ttyX"
The syslinux class initially sets this variable to null but then checks
for a value later.
Lists additional options to add to the syslinux file. You need to set this
variable in your recipe. If you want to list multiple options, separate
the options with a semicolon character (;).
SYSLINUX_OPTS

The syslinux class uses this variable to create a set of options.
Specifies the alternate serial port or turns it off. To turn off serial, set
this variable to an empty string in your recipe. The variable's default
value is set in the syslinux as follows:

SYSLINUX_SERIAL

SYSLINUX_SERIAL ?= "0 115200"
The class checks for and uses the variable as needed.

200

Variables Glossary

An .LSS file used as the background for the VGA boot menu when you
are using the boot menu. You need to set this variable in your recipe.
The syslinux class checks for this variable and if found, the
OpenEmbedded build system installs the splash screen.
SYSLINUX_SPLASH
Specifies the alternate console=tty... kernel boot argument. The
variable's default value is set in the syslinux as follows:

SYSLINUX_SERIAL_TTY

SYSLINUX_SERIAL_TTY ?= "console=ttyS0,115200"

The class checks for and uses the variable as needed.
A list of functions to execute after files are staged into the sysroot.
These functions are usually used to apply additional processing on
the staged files, or to stage additional files.
SYSROOT_PREPROCESS_FUNCS
When inheriting the systemd class, this variable specifies whether
the service you have specified in SYSTEMD_SERVICE should be
started automatically or not. By default, the service is enabled to
automatically start at boot time. The default setting is in the systemd
class as follows:
SYSTEMD_AUTO_ENABLE
SYSTEMD_AUTO_ENABLE ??= "enable"
You can disable the service by setting the variable to "disable".
When inheriting the systemd class, this variable locates the systemd
unit files when they are not found in the main recipe's package. By
default, the SYSTEMD_PACKAGES variable is set such that the systemd
unit files are assumed to reside in the recipes main package:
SYSTEMD_PACKAGES
SYSTEMD_PACKAGES ?= "${PN}"
If these unit files are not in this recipe's main package, you need to
use SYSTEMD_PACKAGES to list the package or packages in which the
build system can find the systemd unit files.
When inheriting the systemd class, this variable specifies the
systemd service name for a package.
When you specify this file in your recipe, use a package name
override to indicate the package to which the value applies. Here is
SYSTEMD_SERVICE
an example from the connman recipe:
SYSTEMD_SERVICE_${PN} = "connman.service"
When using SysVinit [http://www.yoctoproject.org/docs/1.8/devmanual/dev-manual.html#new-recipe-enabling-system-services],
specifies a space-separated list of the virtual terminals that should
be running a getty [http://en.wikipedia.org/wiki/Getty_%28Unix%29]
(allowing login), assuming USE_VT is not set to "0".
SYSVINIT_ENABLED_GETTYS
The default value for SYSVINIT_ENABLED_GETTYS is "1" (i.e. only run
a getty on the first virtual terminal).
201

Variables Glossary

T
This variable points to a directory were BitBake places temporary
files, which consist mostly of task logs and scripts, when building a
particular recipe. The variable is typically set as follows:
T

T = "${WORKDIR}/temp"
The WORKDIR is the directory into which BitBake unpacks and builds
the recipe. The default bitbake.conf file sets this variable.
The T variable is not to be confused with the TMPDIR variable, which
points to the root of the directory tree where BitBake places the
output of an entire build.
The target machine's architecture. The OpenEmbedded build system
supports many architectures. Here is an example list of architectures
supported. This list is by no means complete as the architecture is
configurable:

TARGET_ARCH
arm
i586
x86_64
powerpc
powerpc64
mips
mipsel
For additional information on machine architectures, see the
TUNE_ARCH variable.
Specifies architecture-specific assembler flags for the target system.
TARGET_AS_ARCH is initialized from TUNE_ASARGS by default in the
BitBake configuration file (meta/conf/bitbake.conf):
TARGET_AS_ARCH

TARGET_AS_ARCH = "${TUNE_ASARGS}"

Specifies architecture-specific C compiler flags for the target system.
TARGET_CC_ARCH is initialized from TUNE_CCARGS by default.

Note
TARGET_CC_ARCH

It is a common workaround to append LDFLAGS to
TARGET_CC_ARCH in recipes that build software for the target
that would not otherwise respect the exported LDFLAGS
variable.

This is a specific kernel compiler flag for a CPU or Application Binary
Interface (ABI) tune. The flag is used rarely and only for cases
where a userspace TUNE_CCARGS is not compatible with the kernel
compilation. The TARGET_CC_KERNEL_ARCH variable allows the kernel
(and associated modules) to use a different configuration. See the
TARGET_CC_KERNEL_ARCH
meta/conf/machine/include/arm/feature-arm-thumb.inc file in
the Source Directory [http://www.yoctoproject.org/docs/1.8/devmanual/dev-manual.html#source-directory] for an example.

202

Variables Glossary

Specifies the flags to pass to the C compiler when building for the
target. When building in the target context, CFLAGS is set to the value
of this variable by default.
TARGET_CFLAGS

Additionally, the SDK's environment setup script sets the CFLAGS
variable in the environment to the TARGET_CFLAGS value so that
executables built using the SDK also have the flags applied.
Specifies the flags to pass to the C pre-processor (i.e. to both the C
and the C++ compilers) when building for the target. When building
in the target context, CPPFLAGS is set to the value of this variable
by default.

TARGET_CPPFLAGS
Additionally, the SDK's environment setup script sets the CPPFLAGS
variable in the environment to the TARGET_CPPFLAGS value so that
executables built using the SDK also have the flags applied.
Specifies the flags to pass to the C++ compiler when building for the
target. When building in the target context, CXXFLAGS is set to the
value of this variable by default.
Additionally, the SDK's environment setup script sets the CXXFLAGS
TARGET_CXXFLAGS
variable in the environment to the TARGET_CXXFLAGS value so that
executables built using the SDK also have the flags applied.
Specifies the method for handling FPU code. For FPU-less targets,
which include most ARM CPUs, the variable must be set to "soft". If
not, the kernel emulation gets used, which results in a performance
penalty.
TARGET_FPU
Specifies architecture-specific linker flags for the target system.
TARGET_LD_ARCH is initialized from TUNE_LDARGS by default in the
BitBake configuration file (meta/conf/bitbake.conf):
TARGET_LD_ARCH

TARGET_LD_ARCH = "${TUNE_LDARGS}"

Specifies the flags to pass to the linker when building for the target.
When building in the target context, LDFLAGS is set to the value of
this variable by default.
TARGET_LDFLAGS

Additionally, the SDK's environment setup script sets the LDFLAGS
variable in the environment to the TARGET_LDFLAGS value so that
executables built using the SDK also have the flags applied.
Specifies the target's operating system. The variable can be set to
"linux" for eglibc-based systems and to "linux-uclibc" for uclibc. For
ARM/EABI targets, there are also "linux-gnueabi" and "linux-uclibcgnueabi" values possible.

TARGET_OS
Specifies the GNU standard C library (libc) variant to use during the
build process. This variable replaces POKYLIBC, which is no longer
supported.
TCLIBC

You can select "eglibc" or "uclibc".

Note
This release of the Yocto Project does not support the glibc
implementation of libc.

203

Variables Glossary

TCMODE

Specifies the toolchain selector. TCMODE controls the characteristics
of the generated packages and images by telling the OpenEmbedded
build system which toolchain profile to use. By default, the
OpenEmbedded build system builds its own internal toolchain.
The variable's default value is "default", which uses that internal
toolchain.

Note
If TCMODE is set to a value other than "default", then it is
your responsibility to ensure that the toolchain is compatible
with the default toolchain. Using older or newer versions
of these components might cause build problems. See
the Release Notes [http://www.yoctoproject.org/download/
yocto-project-18-poky-1300] for the specific components
with which the toolchain must be compatible.
With additional layers, it is possible to use a pre-compiled external
toolchain. One example is the Sourcery G++ Toolchain. The support
for this toolchain resides in the separate meta-sourcery layer
at http://github.com/MentorEmbedded/meta-sourcery/. You can use
meta-sourcery as a template for adding support for other external
toolchains.
The TCMODE variable points the build system to a file in conf/distro/
include/tcmode-${TCMODE}.inc. Thus, for meta-sourcery, which
has conf/distro/include/tcmode-external-sourcery.inc, you
would set the variable as follows:
TCMODE ?= "external-sourcery"
The variable is similar to TCLIBC, which controls the variant of the
GNU standard C library (libc) used during the build process: eglibc
or uclibc.
The location the OpenEmbedded build system uses to export tests
when the TEST_EXPORT_ONLY variable is set to "1".
The TEST_EXPORT_DIR variable defaults to "${TMPDIR}/testimage/
${PN}".
TEST_EXPORT_DIR
Specifies to export the tests only. Set this variable to "1" if you do not
want to run the tests but you want them to be exported in a manner
that you to run them outside of the build system.
TEST_EXPORT_ONLY
Automatically runs the series of automated tests for images when an
image is successfully built.

TEST_IMAGE

These tests are written in Python making use of the unittest
module, and the majority of them run commands on the target
system over ssh. You can set this variable to "1" in your
local.conf file in the Build Directory [http://www.yoctoproject.org/
docs/1.8/dev-manual/dev-manual.html#build-directory] to have the
OpenEmbedded build system automatically run these tests after an
image successfully builds:
TEST_IMAGE = "1"
For
more
information
on
enabling,
running,
and
writing
these
tests,
see
the
"Performing
Automated

204

Variables Glossary

Runtime Testing [http://www.yoctoproject.org/docs/1.8/dev-manual/
dev-manual.html#performing-automated-runtime-testing]" section
in
the
Yocto
Project
Development
Manual
and
the
"testimage.bbclass" section.
Holds the SSH log and the boot log for QEMU machines. The
TEST_LOG_DIR variable defaults to "${WORKDIR}/testimage".

Note
TEST_LOG_DIR

Actual test results reside in the task log (log.do_testimage),
which is in the ${WORKDIR}/temp/ directory.

For automated hardware testing, specifies the command to use to
control the power of the target machine under test. Typically, this
command would point to a script that performs the appropriate action
(e.g. interacting with a web-enabled power strip). The specified
command should expect to receive as the last argument "off", "on"
TEST_POWERCONTROL_CMD
or "cycle" specifying to power off, on, or cycle (power off and then
power on) the device, respectively.
For automated hardware testing, specifies additional arguments to
pass through to the command specified in TEST_POWERCONTROL_CMD.
Setting TEST_POWERCONTROL_EXTRA_ARGS is optional. You can use it
if you wish, for example, to separate the machine-specific and nonmachine-specific parts of the arguments.
TEST_POWERCONTROL_EXTRA_ARGS
The time in seconds allowed for an image to boot before automated
runtime tests begin to run against an image. The default timeout
period to allow the boot process to reach the login prompt is 500
seconds. You can specify a different value in the local.conf file.
TEST_QEMUBOOT_TIMEOUT
For more information on testing images, see the "Performing
Automated Runtime Testing [http://www.yoctoproject.org/docs/1.8/
dev-manual/dev-manual.html#performing-automated-runtimetesting]" section in the Yocto Project Development Manual.
For automated hardware testing, specifies the command to use to
connect to the serial console of the target machine under test. This
command simply needs to connect to the serial console and forward
that connection to standard input and output as any normal terminal
program does.
TEST_SERIALCONTROL_CMD
For example, to use the Picocom terminal program on serial device /
dev/ttyUSB0 at 115200bps, you would set the variable as follows:
TEST_SERIALCONTROL_CMD = "picocom /dev/ttyUSB0 -b 115200"
For
automated
hardware
testing,
specifies
additional
arguments to pass through to the command specified in
TEST_SERIALCONTROL_CMD.
Setting
TEST_SERIALCONTROL_EXTRA_ARGS is optional. You can use it if
you wish, for example, to separate the machine-specific and nonTEST_SERIALCONTROL_EXTRA_ARGS
machine-specific parts of the command.
The IP address of the build machine (host machine). This IP address
is usually automatically detected. However, if detection fails, this
variable needs to be set to the IP address of the build machine (i.e.
where the build is taking place).
TEST_SERVER_IP

Note
The TEST_SERVER_IP variable is only used for a small number
of tests such as the "smart" test suite, which needs to
download packages from DEPLOY_DIR/rpm.

205

Variables Glossary

Specifies the target controller to use when running tests against a
test image. The default controller to use is "qemu":

TEST_TARGET

TEST_TARGET = "qemu"
A target controller is a class that defines how an image gets
deployed on a target and how a target is started. A layer can
extend the controllers by adding a module in the layer's /lib/oeqa/
controllers directory and by inheriting the BaseTarget class, which
is an abstract class that cannot be used as a value of TEST_TARGET.
You can provide the following arguments with TEST_TARGET:
• "qemu" and "QemuTarget": Boots a QEMU image and
runs
the
tests.
See
the
"Enabling
Runtime
Tests
on QEMU [http://www.yoctoproject.org/docs/1.8/dev-manual/devmanual.html#qemu-image-enabling-tests]" section in the Yocto
Project Development Manual for more information.
• "simpleremote" and "SimpleRemoteTarget": Runs the tests on
target hardware that is already up and running. The hardware can
be on the network or it can be a device running an image on QEMU.
You must also set TEST_TARGET_IP when you use "simpleremote"
or "SimpleRemoteTarget".

Note
This
argument
is
defined
in
meta/lib/oeqa/
targetcontrol.py. The small caps names are kept for
compatibility reasons.
• "GummibootTarget": Automatically deploys and runs tests on an
EFI-enabled machine that has a master image installed.

Note
This argument is defined in meta/lib/oeqa/controllers/
masterimage.py.
For information on running tests on hardware, see the "Enabling
Runtime Tests on Hardware [http://www.yoctoproject.org/docs/1.8/
dev-manual/dev-manual.html#hardware-image-enabling-tests]"
section in the Yocto Project Development Manual.
The IP address of your hardware under test. The TEST_TARGET_IP
variable has no effect when TEST_TARGET is set to "qemu".

TEST_TARGET_IP

When you specify the IP address, you can also include a port. Here
is an example:
TEST_TARGET_IP = "192.168.1.4:2201"
Specifying a port is useful when SSH is started on a non-standard
port or in cases when your hardware under test is behind a firewall or
network that is not directly accessible from your host and you need
to do port address translation.
An ordered list of tests (modules) to run against an image when
performing automated runtime testing.

TEST_SUITES
206

Variables Glossary

The OpenEmbedded build system provides a core set of tests that
can be used against images.

Note
Currently, there is only support for running these tests under
QEMU.
Tests include ping, ssh, df among others. You can add your own tests
to the list of tests by appending TEST_SUITES as follows:
TEST_SUITES_append = " mytest"
Alternatively, you can provide the "auto" option to have all applicable
tests run against the image.
TEST_SUITES_append = " auto"
Using this option causes the build system to automatically run tests
that are applicable to the image. Tests that are not applicable are
skipped.
The order in which tests are run is important. Tests that depend on
another test must appear later in the list than the test on which they
depend. For example, if you append the list of tests with two tests
(test_A and test_B) where test_B is dependent on test_A, then
you must order the tests as follows:
TEST_SUITES = " test_A test_B"
For more information on testing images, see the "Performing
Automated Runtime Testing [http://www.yoctoproject.org/docs/1.8/
dev-manual/dev-manual.html#performing-automated-runtimetesting]" section in the Yocto Project Development Manual.
The directory in which the file BitBake is currently parsing is located.
Do not manually set this variable.

THISDIR

TMPDIR

This variable is the base directory the OpenEmbedded build system
uses for all build output and intermediate files (other than the
shared state cache). By default, the TMPDIR variable points to tmp
within the Build Directory [http://www.yoctoproject.org/docs/1.8/devmanual/dev-manual.html#build-directory].
If you want to establish this directory in a location
other than the default, you can uncomment and edit the
following statement in the conf/local.conf file in the
Source Directory [http://www.yoctoproject.org/docs/1.8/dev-manual/
dev-manual.html#source-directory]:
#TMPDIR = "${TOPDIR}/tmp"
An example use for this scenario is to set TMPDIR to a local disk, which
does not use NFS, while having the Build Directory use NFS.

207

Variables Glossary

The filesystem used by TMPDIR must have standard filesystem
semantics (i.e. mixed-case files are unique, POSIX file locking, and
persistent inodes). Due to various issues with NFS and bugs in some
implementations, NFS does not meet this minimum requirement.
Consequently, TMPDIR cannot be on NFS.
This variable lists packages the OpenEmbedded build system
uses when building an SDK, which contains a cross-development
environment. The packages specified by this variable are part of the
toolchain set that runs on the SDKMACHINE, and each package should
usually have the prefix "nativesdk-". When building an SDK using
TOOLCHAIN_HOST_TASK
bitbake -c populate_sdk , a default list of packages
is set in this variable, but you can add additional packages to the list.
For background information on cross-development toolchains in
the Yocto Project development environment, see the "CrossDevelopment Toolchain Generation" section. For information on
setting up a cross-development environment, see the "Installing
the ADT and Toolchains [http://www.yoctoproject.org/docs/1.8/adtmanual/adt-manual.html#installing-the-adt]" section in the Yocto
Project Application Developer's Guide.
This variable lists packages the OpenEmbedded build system uses
when it creates the target part of an SDK (i.e. the part built for the
target hardware), which includes libraries and headers.
For background information on cross-development toolchains in
TOOLCHAIN_TARGET_TASK
the Yocto Project development environment, see the "CrossDevelopment Toolchain Generation" section. For information on
setting up a cross-development environment, see the "Installing
the ADT and Toolchains [http://www.yoctoproject.org/docs/1.8/adtmanual/adt-manual.html#installing-the-adt]" section in the Yocto
Project Application Developer's Guide.

TOPDIR

The
top-level
Build
Directory
[http://www.yoctoproject.org/
docs/1.8/dev-manual/dev-manual.html#build-directory].
BitBake
automatically sets this variable when you initialize your build
environment using either oe-init-build-env or oe-init-buildenv-memres.
A sanitized version of TARGET_ARCH. This variable is used where the
architecture is needed in a value where underscores are not allowed,
for example within package filenames. In this case, dash characters
replace any underscore characters used in TARGET_ARCH.

TRANSLATED_TARGET_ARCH
Do not edit this variable.
The GNU canonical architecture for a specific architecture (i.e. arm,
armeb, mips, mips64, and so forth). BitBake uses this value to setup
configuration.
TUNE_ARCH

TUNE_ARCH definitions are specific to a given architecture.
The definitions can be a single static definition, or can
be dynamically adjusted. You can see details for a given
CPU family by looking at the architecture's README file. For
example, the meta/conf/machine/include/mips/README file in
the Source Directory [http://www.yoctoproject.org/docs/1.8/devmanual/dev-manual.html#source-directory] provides information for
TUNE_ARCH specific to the mips architecture.
TUNE_ARCH is tied closely to TARGET_ARCH, which defines the target
machine's architecture. The BitBake configuration file (meta/conf/
bitbake.conf) sets TARGET_ARCH as follows:

208

Variables Glossary

TARGET_ARCH = "${TUNE_ARCH}"
The following list, which is by no means complete since architectures
are configurable, shows supported machine architectures:
arm
i586
x86_64
powerpc
powerpc64
mips
mipsel

TUNE_ASARGS

Specifies architecture-specific assembler flags for the target system.
The set of flags is based on the selected tune features.
TUNE_ASARGS is set using the tune include files, which are typically
under meta/conf/machine/include/ and are influenced through
TUNE_FEATURES. For example, the meta/conf/machine/include/
x86/arch-x86.inc file defines the flags for the x86 architecture as
follows:

TUNE_ASARGS += "${@bb.utils.contains("TUNE_FEATURES", "mx32", "-x3

Note
Board Support Packages (BSPs) select the tune. The selected
tune, in turn, affects the tune variables themselves (i.e. the
tune can supply its own set of flags).

TUNE_CCARGS

Specifies architecture-specific C compiler flags for the target
system. The set of flags is based on the selected tune features.
TUNE_CCARGS is set using the tune include files, which are typically
under meta/conf/machine/include/ and are influenced through
TUNE_FEATURES.

Note
Board Support Packages (BSPs) select the tune. The selected
tune, in turn, affects the tune variables themselves (i.e. the
tune can supply its own set of flags).

TUNE_LDARGS

Specifies architecture-specific linker flags for the target system. The
set of flags is based on the selected tune features. TUNE_LDARGS is
set using the tune include files, which are typically under meta/conf/
machine/include/ and are influenced through TUNE_FEATURES. For
example, the meta/conf/machine/include/x86/arch-x86.inc file
defines the flags for the x86 architecture as follows:
TUNE_LDARGS += "${@bb.utils.contains("TUNE_FEATURES", "mx32", "-m

Note
Board Support Packages (BSPs) select the tune. The selected
tune, in turn, affects the tune variables themselves (i.e. the
tune can supply its own set of flags).

209

Variables Glossary

Features used to "tune" a compiler for optimal use given a specific
processor. The features are defined within the tune files and allow
arguments (i.e. TUNE_*ARGS) to be dynamically generated based on
the features.
TUNE_FEATURES The OpenEmbedded build system verifies the features to be sure
they are not conflicting and that they are supported.
The BitBake configuration file (meta/conf/bitbake.conf) defines
TUNE_FEATURES as follows:
TUNE_FEATURES ??= "${TUNE_FEATURES_tune-${DEFAULTTUNE}}"
See the DEFAULTTUNE variable for more information.
The package architecture understood by the packaging system to
define the architecture, ABI, and tuning of output packages. The
specific tune is defined using the "_tune" override as follows:
TUNE_PKGARCH

TUNE_PKGARCH_tune-tune = "tune"
These tune-specific package architectures are defined in the machine
include files. Here is an example of the "core2-32" tuning as used in
the meta/conf/machine/include/tune-core2.inc file:
TUNE_PKGARCH_tune-core2-32 = "core2-32"

TUNEABI

An underlying Application Binary Interface (ABI) used by a particular
tuning in a given toolchain layer. Providers that use prebuilt libraries
can use the TUNEABI, TUNEABI_OVERRIDE, and TUNEABI_WHITELIST
variables to check compatibility of tunings against their selection of
libraries.
If TUNEABI is undefined, then every tuning is allowed. See the sanity
class to see how the variable is used.
If set, the OpenEmbedded system ignores the TUNEABI_WHITELIST
variable. Providers that use prebuilt libraries can use the
TUNEABI_OVERRIDE, TUNEABI_WHITELIST, and TUNEABI variables to
check compatibility of a tuning against their selection of libraries.

TUNEABI_OVERRIDE
See the sanity class to see how the variable is used.
A whitelist of permissible TUNEABI values. If TUNEABI_WHITELIST is
not set, all tunes are allowed. Providers that use prebuilt libraries
can use the TUNEABI_WHITELIST, TUNEABI_OVERRIDE, and TUNEABI
variables to check compatibility of a tuning against their selection of
libraries.
TUNEABI_WHITELIST
See the sanity class to see how the variable is used.
Specifies CPU or Application Binary Interface (ABI) tuning features
that conflict with feature.
Known tuning conflicts are specified in the machine include
files in the Source Directory [http://www.yoctoproject.org/
TUNECONFLICTS[feature]
docs/1.8/dev-manual/dev-manual.html#source-directory]. Here is
an example from the meta/conf/machine/include/mips/archmips.inc include file that lists the "o32" and "n64" features as
conflicting with the "n32" feature:

210

Variables Glossary

TUNECONFLICTS[n32] = "o32 n64"
Specifies a valid CPU or Application Binary Interface (ABI) tuning
feature. The specified feature is stored as a flag. Valid features are
specified in the machine include files (e.g. meta/conf/machine/
include/arm/arch-arm.inc). Here is an example from that file:
TUNEVALID[feature]
TUNEVALID[bigendian] = "Enable big-endian mode."
See
the
machine
include
files
in
the
Source
Directory
[http://www.yoctoproject.org/docs/1.8/dev-manual/devmanual.html#source-directory] for these features.

U
Configures the UBOOT_MACHINE and can also define IMAGE_FSTYPES
for individual cases.
Following is an example from the meta-fsl-arm layer.
UBOOT_CONFIG
UBOOT_CONFIG ??= "sd"
UBOOT_CONFIG[sd] = "mx6qsabreauto_config,sdcard"
UBOOT_CONFIG[eimnor] = "mx6qsabreauto_eimnor_config"
UBOOT_CONFIG[nand] = "mx6qsabreauto_nand_config,ubifs"
UBOOT_CONFIG[spinor] = "mx6qsabreauto_spinor_config"
In this example, "sd" is selected as the configuration of the
possible four for the UBOOT_MACHINE. The "sd" configuration defines
"mx6qsabreauto_config" as the value for UBOOT_MACHINE, while the
"sdcard" specifies the IMAGE_FSTYPES to use for the U-boot image.
For more information on how the UBOOT_CONFIG is handled, see
the uboot-config [http://git.yoctoproject.org/cgit/cgit.cgi/poky/tree/
meta/classes/uboot-config.bbclass] class.
Specifies the entry point for the U-Boot image. During U-Boot image
creation, the UBOOT_ENTRYPOINT variable is passed as a commandline parameter to the uboot-mkimage utility.
UBOOT_ENTRYPOINT
Specifies the load address for the U-Boot image. During U-Boot image
creation, the UBOOT_LOADADDRESS variable is passed as a commandline parameter to the uboot-mkimage utility.
UBOOT_LOADADDRESS
Appends a string to the name of the local version of the U-Boot
image. For example, assuming the version of the U-Boot image built
was "2013.10, the full version string reported by U-Boot would be
"2013.10-yocto" given the following statement:
UBOOT_LOCALVERSION
UBOOT_LOCALVERSION = "-yocto"

211

Variables Glossary

Specifies the value passed on the make command line when building a
U-Boot image. The value indicates the target platform configuration.
You typically set this variable from the machine configuration file (i.e.
conf/machine/machine_name.conf).
UBOOT_MACHINE

Please see the "Selection of Processor Architecture and Board Type"
section in the U-Boot README for valid values for this variable.
Specifies the target called in the Makefile. The default target is "all".

UBOOT_MAKE_TARGET
Points to the generated U-Boot extension. For example, u-boot.sb
has a .sb extension.
The default U-Boot extension is .bin
UBOOT_SUFFIX

UBOOT_TARGET

USE_VT

Specifies the target used for building U-Boot. The target is passed
directly as part of the "make" command (e.g. SPL and AIS). If you do
not specifically set this variable, the OpenEmbedded build process
passes and uses "all" for the target during the U-Boot building
process.
When using SysVinit [http://www.yoctoproject.org/docs/1.8/devmanual/dev-manual.html#new-recipe-enabling-system-services],
determines whether or not to run a getty [http://en.wikipedia.org/
wiki/Getty_%28Unix%29] on any virtual terminals in order to enable
logging in through those terminals.
The default value used for USE_VT is "1" when no default value is
specifically set. Typically, you would set USE_VT to "0" in the machine
configuration file for machines that do not have a graphical display
attached and therefore do not need virtual terminal functionality.
A list of classes to globally inherit. These classes are used by
the OpenEmbedded build system to enable extra features (e.g.
buildstats, image-mklibs, and so forth).

USER_CLASSES

The default list is set in your local.conf file:
USER_CLASSES ?= "buildstats image-mklibs image-prelink"
For more information, see meta-yocto/conf/local.conf.sample
in the Source Directory [http://www.yoctoproject.org/docs/1.8/devmanual/dev-manual.html#source-directory].
Forces the OpenEmbedded build system to produce an error if the
user identification (uid) and group identification (gid) values are not
defined in files/passwd and files/group files.

The default behavior for the build system is to dynamically apply uid
USERADD_ERROR_DYNAMIC
and gid values. Consequently, the USERADD_ERROR_DYNAMIC variable
is by default not set. If you plan on using statically assigned gid and
uid values, you should set the USERADD_ERROR_DYNAMIC variable in
your local.conf file as follows:
USERADD_ERROR_DYNAMIC = "1"

212

Variables Glossary

Overriding the default behavior implies you are going to
also take steps to set static uid and gid values through
use of the USERADDEXTENSION, USERADD_UID_TABLES, and
USERADD_GID_TABLES variables.
Specifies a password file to use for obtaining static group
identification (gid) values when the OpenEmbedded build system
adds a group to the system during package installation.
When applying static group identification (gid) values, the
USERADD_GID_TABLES
OpenEmbedded build system looks in BBPATH for a files/group file
and then applies those uid values. Set the variable as follows in your
local.conf file:
USERADD_GID_TABLES = "files/group"

Note
Setting the USERADDEXTENSION variable to "useraddstaticids" causes the build system to use static gid values.
When inheriting the useradd class, this variable specifies the
individual packages within the recipe that require users and/or
groups to be added.
You must set this variable if the recipe inherits the class. For example,
USERADD_PACKAGES
the following enables adding a user for the main package in a recipe:
USERADD_PACKAGES = "${PN}"

Note
If follows that if you are going to use the USERADD_PACKAGES
variable, you need to set one or more of the USERADD_PARAM,
GROUPADD_PARAM, or GROUPMEMS_PARAM variables.
When inheriting the useradd class, this variable specifies for
a package what parameters should be passed to the useradd
command if you wish to add a user to the system when the package
is installed.
USERADD_PARAM Here is an example from the dbus recipe:

USERADD_PARAM_${PN} = "--system --home ${localstatedir}/lib/dbus \
--no-create-home --shell /bin/false \
--user-group messagebus"
For information on the standard Linux shell command useradd, see
http://linux.die.net/man/8/useradd.
Specifies a password file to use for obtaining static user identification
(uid) values when the OpenEmbedded build system adds a user to
the system during package installation.
When applying static user identification (uid) values, the
USERADD_UID_TABLES
OpenEmbedded build system looks in BBPATH for a files/passwd file
and then applies those uid values. Set the variable as follows in your
local.conf file:
USERADD_UID_TABLES = "files/passwd"

213

Variables Glossary

Note
Setting the USERADDEXTENSION variable to "useraddstaticids" causes the build system to use static uid values.
When set to "useradd-staticids", causes the OpenEmbedded build
system to base all user and group additions on a static passwd and
group files found in BBPATH.
To use static user identification (uid) and group identification (gid)
USERADDEXTENSION
values, set the variable as follows in your local.conf file:
USERADDEXTENSION = "useradd-staticids"

Note
Setting this variable to use static uid and gid values causes
the OpenEmbedded build system to employ the useraddstaticids class.
If you use static uid and gid information, you must also
specify the files/passwd and files/group files by setting
the USERADD_UID_TABLES and USERADD_GID_TABLES variables.
Additionally, you should also set the USERADD_ERROR_DYNAMIC
variable.

W
Specifies the quality assurance checks whose failures are reported as
warnings by the OpenEmbedded build system. You set this variable
in your distribution configuration file. For a list of the checks you can
control with this variable, see the "insane.bbclass" section.
WARN_QA
The pathname of the work directory in which the OpenEmbedded
build system builds a recipe. This directory is located within the
TMPDIR directory structure and is specific to the recipe being built
and the system for which it is being built.
WORKDIR

The WORKDIR directory is defined as follows:

${TMPDIR}/work/${MULTIMACH_TARGET_SYS}/${PN}/${EXTENDPE}${PV}-${PR
The actual directory depends on several things:
• TMPDIR: The top-level build output directory
• MULTIMACH_TARGET_SYS: The target system identifier
• PN: The recipe name
• EXTENDPE: The epoch - (if PE is not specified, which is usually the
case for most recipes, then EXTENDPE is blank)
• PV: The recipe version
• PR: The recipe revision
As an example, assume a Source Directory top-level folder name
poky, a default Build Directory at poky/build, and a qemux86-pokylinux machine target system. Furthermore, suppose your recipe is

214

Variables Glossary

named foo_1.3.0-r0.bb. In this case, the work directory the build
system uses to build the package would be as follows:
poky/build/tmp/work/qemux86-poky-linux/foo/1.3.0-r0

X
Specifies the packages that should be installed to provide an X server
and drivers for the current machine, assuming your image directly
includes packagegroup-core-x11-xserver or, perhaps indirectly,
includes "x11-base" in IMAGE_FEATURES.
XSERVER

The default value of XSERVER, if not specified in the machine
configuration, is "xserver-xorg xf86-video-fbdev xf86-input-evdev".

215

Chapter 13. Variable Context
While you can use most variables in almost any context such as .conf, .bbclass, .inc, and .bb
files, some variables are often associated with a particular locality or context. This chapter describes
some common associations.

13.1. Configuration
The following subsections provide lists of variables whose context is configuration: distribution,
machine, and local.

13.1.1. Distribution (Distro)
This section lists variables whose configuration context is the distribution, or distro.
• DISTRO
• DISTRO_NAME
• DISTRO_VERSION
• MAINTAINER
• PACKAGE_CLASSES
• TARGET_OS
• TARGET_FPU
• TCMODE
• TCLIBC

13.1.2. Machine
This section lists variables whose configuration context is the machine.
• TARGET_ARCH
• SERIAL_CONSOLES
• PACKAGE_EXTRA_ARCHS
• IMAGE_FSTYPES
• MACHINE_FEATURES
• MACHINE_EXTRA_RDEPENDS
• MACHINE_EXTRA_RRECOMMENDS
• MACHINE_ESSENTIAL_EXTRA_RDEPENDS
• MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS

13.1.3. Local
This section lists variables whose configuration context is the local configuration through the
local.conf file.
• DISTRO
• MACHINE
• DL_DIR

216

Variable Context

• BBFILES
• EXTRA_IMAGE_FEATURES
• PACKAGE_CLASSES
• BB_NUMBER_THREADS
• BBINCLUDELOGS
• ENABLE_BINARY_LOCALE_GENERATION

13.2. Recipes
The following subsections provide lists of variables whose context is recipes: required, dependencies,
path, and extra build information.

13.2.1. Required
This section lists variables that are required for recipes.
• LICENSE
• LIC_FILES_CHKSUM
• SRC_URI - used in recipes that fetch local or remote files.

13.2.2. Dependencies
This section lists variables that define recipe dependencies.
• DEPENDS
• RDEPENDS
• RRECOMMENDS
• RCONFLICTS
• RREPLACES

13.2.3. Paths
This section lists variables that define recipe paths.
• WORKDIR
• S
• FILES

13.2.4. Extra Build Information
This section lists variables that define extra build information for recipes.
• EXTRA_OECMAKE
• EXTRA_OECONF
• EXTRA_OEMAKE
• PACKAGES
• DEFAULT_PREFERENCE

217

Chapter 14. FAQ
14.1. How does Poky differ from OpenEmbedded [http://www.openembedded.org]?
The term "Poky [http://www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#poky]"
refers to the specific reference build system that the Yocto Project provides. Poky is based
on OE-Core [http://www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#oe-core] and
BitBake [http://www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#bitbake-term].
Thus, the generic term used here for the build system is the "OpenEmbedded build system."
Development in the Yocto Project using Poky is closely tied to OpenEmbedded, with changes
always being merged to OE-Core or BitBake first before being pulled back into Poky. This practice
benefits both projects immediately.
14.2. My development system does not meet the required Git, tar, and Python versions. In particular,
I do not have Python 2.7.3 or greater, or I do have Python 3.x, which is specifically not supported
by the Yocto Project. Can I still use the Yocto Project?
You can get the required tools on your host development system a couple different ways (i.e.
building a tarball or downloading a tarball). See the "Required Git, tar, and Python Versions"
section for steps on how to update your build tools.
14.3. How can you claim Poky / OpenEmbedded-Core is stable?
There are three areas that help with stability;
• The Yocto Project team keeps OE-Core [http://www.yoctoproject.org/docs/1.8/dev-manual/
dev-manual.html#oe-core] small and focused, containing around 830 recipes as opposed to
the thousands available in other OpenEmbedded community layers. Keeping it small makes
it easy to test and maintain.
• The Yocto Project team runs manual and automated tests using a small, fixed set of reference
hardware as well as emulated targets.
• The Yocto Project uses an autobuilder, which provides continuous build and integration tests.
14.4. How do I get support for my board added to the Yocto Project?
Support for an additional board is added by creating a Board Support Package
(BSP) layer for it. For more information on how to create a BSP layer, see the
"Understanding and Creating Layers [http://www.yoctoproject.org/docs/1.8/dev-manual/devmanual.html#understanding-and-creating-layers]" section in the Yocto Project Development
Manual and the Yocto Project Board Support Package (BSP) Developer's Guide [http://
www.yoctoproject.org/docs/1.8/bsp-guide/bsp-guide.html].
Usually, if the board is not completely exotic, adding support in the Yocto Project is fairly
straightforward.
14.5. Are there any products built using the OpenEmbedded build system?
The software running on the Vernier LabQuest [http://vernier.com/labquest/] is built using the
OpenEmbedded build system. See the Vernier LabQuest [http://www.vernier.com/products/
interfaces/labq/] website for more information. There are a number of pre-production devices
using the OpenEmbedded build system and the Yocto Project team announces them as soon
as they are released.
14.6. What does the OpenEmbedded build system produce as output?
Because you can use the same set of recipes to create output of various formats, the output of
an OpenEmbedded build depends on how you start it. Usually, the output is a flashable image
ready for the target device.
14.7. How do I add my package to the Yocto Project?
To add a package, you need to create a BitBake recipe. For information on how to create
a BitBake recipe, see the "Writing a New Recipe [http://www.yoctoproject.org/docs/1.8/dev-

218

FAQ

manual/dev-manual.html#new-recipe-writing-a-new-recipe]" in the Yocto Project Development
Manual.
14.8. Do I have to reflash my entire board with a new Yocto Project image when recompiling a
package?
The OpenEmbedded build system can build packages in various formats such as IPK for OPKG,
Debian package (.deb), or RPM. You can then upgrade the packages using the package tools on
the device, much like on a desktop distribution such as Ubuntu or Fedora. However, package
management on the target is entirely optional.
14.9. What is GNOME Mobile and what is the difference between GNOME Mobile and GNOME?
GNOME Mobile is a subset of the GNOME [http://www.gnome.org] platform targeted at mobile
and embedded devices. The main difference between GNOME Mobile and standard GNOME is
that desktop-orientated libraries have been removed, along with deprecated libraries, creating
a much smaller footprint.
14.10.I see the error 'chmod: XXXXX new permissions are r-xrwxrwx, not r-xr-xr-x'. What
is wrong?
You are probably running the build on an NTFS filesystem. Use ext2, ext3, or ext4 instead.
14.11.I see lots of 404 responses for files on /sources/*. Is something wrong?
Nothing is wrong. The OpenEmbedded build system checks any configured source mirrors
before downloading from the upstream sources. The build system does this searching for both
source archives and pre-checked out versions of SCM-managed software. These checks help
in large installations because it can reduce load on the SCM servers themselves. The address
above is one of the default mirrors configured into the build system. Consequently, if an
upstream source disappears, the team can place sources there so builds continue to work.
14.12.I have machine-specific data in a package for one machine only but the package is being marked
as machine-specific in all cases, how do I prevent this?
Set SRC_URI_OVERRIDES_PACKAGE_ARCH = "0" in the .bb file but make sure the package
is manually marked as machine-specific for the case that needs it. The code that handles
SRC_URI_OVERRIDES_PACKAGE_ARCH is in the meta/classes/base.bbclass file.
14.13.I'm behind a firewall and need to use a proxy server. How do I do that?
Most source fetching by the OpenEmbedded build system is done by wget and you therefore
need to specify the proxy settings in a .wgetrc file in your home directory. Here are some
example settings:
http_proxy = http://proxy.yoyodyne.com:18023/
ftp_proxy = http://proxy.yoyodyne.com:18023/
The Yocto Project also includes a site.conf.sample file that shows how to configure CVS and
Git proxy servers if needed.
14.14.What’s the difference between target and target-native?
The *-native targets are designed to run on the system being used for the build. These are
usually tools that are needed to assist the build in some way such as quilt-native, which is
used to apply patches. The non-native version is the one that runs on the target device.
14.15.I'm seeing random build failures. Help?!
If the same build is failing in totally different and random ways, the most likely explanation is:
• The hardware you are running the build on has some problem.
• You are running the build under virtualization, in which case the virtualization probably has
bugs.

219

FAQ

The OpenEmbedded build system processes a massive amount of data that causes lots of
network, disk and CPU activity and is sensitive to even single-bit failures in any of these areas.
True random failures have always been traced back to hardware or virtualization issues.
14.16.What do we need to ship for license compliance?
This is a difficult question and you need to consult your lawyer for the answer for your specific
case. It is worth bearing in mind that for GPL compliance, there needs to be enough information
shipped to allow someone else to rebuild and produce the same end result you are shipping.
This means sharing the source code, any patches applied to it, and also any configuration
information about how that package was configured and built.
You
can
find
more
information
on
licensing
in
the
"Licensing
[http://www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#licensing]"
and
"Maintaining
Open
Source
License
Compliance
During
Your
Product's
Lifecycle
[http://www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#maintainingopen-source-license-compliance-during-your-products-lifecycle]" sections, both of which are in
the Yocto Project Development Manual.
14.17.How do I disable the cursor on my touchscreen device?
You need to create a form factor file as described in the "Miscellaneous BSP-Specific
Recipe Files [http://www.yoctoproject.org/docs/1.8/bsp-guide/bsp-guide.html#bsp-filelayoutmisc-recipes]" section in the Yocto Project Board Support Packages (BSP) Developer's Guide.
Set the HAVE_TOUCHSCREEN variable equal to one as follows:
HAVE_TOUCHSCREEN=1
14.18.How do I make sure connected network interfaces are brought up by default?
The default interfaces file provided by the netbase recipe does not automatically bring up
network interfaces. Therefore, you will need to add a BSP-specific netbase that includes an
interfaces file. See the "Miscellaneous BSP-Specific Recipe Files [http://www.yoctoproject.org/
docs/1.8/bsp-guide/bsp-guide.html#bsp-filelayout-misc-recipes]" section in the Yocto Project
Board Support Packages (BSP) Developer's Guide for information on creating these types of
miscellaneous recipe files.
For example, add the following files to your layer:
meta-MACHINE/recipes-bsp/netbase/netbase/MACHINE/interfaces
meta-MACHINE/recipes-bsp/netbase/netbase_5.0.bbappend
14.19.How do I create images with more free space?
By default, the OpenEmbedded build system creates images that are 1.3 times the size of the
populated root filesystem. To affect the image size, you need to set various configurations:
• Image Size: The OpenEmbedded build system uses the IMAGE_ROOTFS_SIZE variable to define
the size of the image in Kbytes. The build system determines the size by taking into account
the initial root filesystem size before any modifications such as requested size for the image
and any requested additional free disk space to be added to the image.
• Overhead: Use the IMAGE_OVERHEAD_FACTOR variable to define the multiplier that the build
system applies to the initial image size, which is 1.3 by default.
• Additional Free Space: Use the IMAGE_ROOTFS_EXTRA_SPACE variable to add additional free
space to the image. The build system adds this space to the image after it determines its
IMAGE_ROOTFS_SIZE.
14.20.Why don't you support directories with spaces in the pathnames?
The Yocto Project team has tried to do this before but too many of the tools the OpenEmbedded
build system depends on, such as autoconf, break when they find spaces in pathnames. Until
that situation changes, the team will not support spaces in pathnames.

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FAQ

14.21.How do I use an external toolchain?
The toolchain configuration is very flexible and customizable. It is primarily controlled with the
TCMODE variable. This variable controls which tcmode-*.inc file to include from the meta/conf/
distro/include directory within the Source Directory [http://www.yoctoproject.org/docs/1.8/
dev-manual/dev-manual.html#source-directory].
The default value of TCMODE is "default", which tells the OpenEmbedded build system to use
its internally built toolchain (i.e. tcmode-default.inc). However, other patterns are accepted.
In particular, "external-*" refers to external toolchains. One example is the Sourcery G++
Toolchain. The support for this toolchain resides in the separate meta-sourcery layer at http://
github.com/MentorEmbedded/meta-sourcery/.
In addition to the toolchain configuration, you also need a corresponding toolchain recipe file.
This recipe file needs to package up any pre-built objects in the toolchain such as libgcc,
libstdcc++, any locales, and libc.
14.22.How does the OpenEmbedded build system obtain source code and will it work behind my
firewall or proxy server?
The way the build system obtains source code is highly configurable. You can setup the build
system to get source code in most environments if HTTP transport is available.
When the build system searches for source code, it first tries the local download directory. If
that location fails, Poky tries PREMIRRORS, the upstream source, and then MIRRORS in that order.
Assuming your distribution is "poky", the OpenEmbedded build system uses the Yocto Project
source PREMIRRORS by default for SCM-based sources, upstreams for normal tarballs, and then
falls back to a number of other mirrors including the Yocto Project source mirror if those fail.
As an example, you could add a specific server for the build system to attempt before any
others by adding something like the following to the local.conf configuration file:
PREMIRRORS_prepend = "\
git://.*/.* http://www.yoctoproject.org/sources/ \n \
ftp://.*/.* http://www.yoctoproject.org/sources/ \n \
http://.*/.* http://www.yoctoproject.org/sources/ \n \
https://.*/.* http://www.yoctoproject.org/sources/ \n"
These changes cause the build system to intercept Git, FTP, HTTP, and HTTPS requests and
direct them to the http:// sources mirror. You can use file:// URLs to point to local directories
or network shares as well.
Aside from the previous technique, these options also exist:
BB_NO_NETWORK = "1"
This statement tells BitBake to issue an error instead of trying to access the Internet. This
technique is useful if you want to ensure code builds only from local sources.
Here is another technique:
BB_FETCH_PREMIRRORONLY = "1"
This statement limits the build system to pulling source from the PREMIRRORS only. Again, this
technique is useful for reproducing builds.
Here is another technique:
BB_GENERATE_MIRROR_TARBALLS = "1"

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FAQ

This statement tells the build system to generate mirror tarballs. This technique is useful if you
want to create a mirror server. If not, however, the technique can simply waste time during
the build.
Finally, consider an example where you are behind an HTTP-only firewall. You could make the
following changes to the local.conf configuration file as long as the PREMIRRORS server is
current:
PREMIRRORS_prepend = "\
ftp://.*/.* http://www.yoctoproject.org/sources/ \n \
http://.*/.* http://www.yoctoproject.org/sources/ \n \
https://.*/.* http://www.yoctoproject.org/sources/ \n"
BB_FETCH_PREMIRRORONLY = "1"
These changes would cause the build system to successfully fetch source over HTTP and any
network accesses to anything other than the PREMIRRORS would fail.
The build system also honors the standard shell environment variables http_proxy, ftp_proxy,
https_proxy, and all_proxy to redirect requests through proxy servers.

Note
You can find more information on the "Working Behind a Network Proxy [https://
wiki.yoctoproject.org/wiki/Working_Behind_a_Network_Proxy]" Wiki page.
14.23.Can I get rid of build output so I can start over?
Yes - you can easily do this. When you use BitBake to build an image, all the build output
goes into the directory created when you run the build environment setup script (i.e. oeinit-build-env or oe-init-build-env-memres). By default, this Build Directory [http://
www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#build-directory] is named build
but can be named anything you want.
Within the Build Directory, is the tmp directory. To remove all the build output yet preserve any
source code or downloaded files from previous builds, simply remove the tmp directory.
14.24.Why do ${bindir} and ${libdir} have strange values for -native recipes?
Executables and libraries might need to be used from a directory other than the directory
into which they were initially installed. Complicating this situation is the fact that sometimes
these executables and libraries are compiled with the expectation of being run from that initial
installation target directory. If this is the case, moving them causes problems.
This scenario is a fundamental problem for package maintainers of mainstream Linux
distributions as well as for the OpenEmbedded build system. As such, a well-established
solution exists. Makefiles, Autotools configuration scripts, and other build systems are expected
to respect environment variables such as bindir, libdir, and sysconfdir that indicate where
executables, libraries, and data reside when a program is actually run. They are also expected
to respect a DESTDIR environment variable, which is prepended to all the other variables when
the build system actually installs the files. It is understood that the program does not actually
run from within DESTDIR.
When the OpenEmbedded build system uses a recipe to build a target-architecture program
(i.e. one that is intended for inclusion on the image being built), that program eventually runs
from the root file system of that image. Thus, the build system provides a value of "/usr/bin"
for bindir, a value of "/usr/lib" for libdir, and so forth.
Meanwhile, DESTDIR is a path within the Build Directory [http://www.yoctoproject.org/docs/1.8/
dev-manual/dev-manual.html#build-directory]. However, when the recipe builds a native
program (i.e. one that is intended to run on the build machine), that program is never installed
directly to the build machine's root file system. Consequently, the build system uses paths
within the Build Directory for DESTDIR, bindir and related variables. To better understand this,
consider the following two paths where the first is relatively normal and the second is not:

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FAQ

Note
Due to these lengthy examples, the paths are artificially broken across lines for
readability.
/home/maxtothemax/poky-bootchart2/build/tmp/work/i586-poky-linux/zlib/
1.2.8-r0/sysroot-destdir/usr/bin
/home/maxtothemax/poky-bootchart2/build/tmp/work/x86_64-linux/
zlib-native/1.2.8-r0/sysroot-destdir/home/maxtothemax/poky-bootchart2/
build/tmp/sysroots/x86_64-linux/usr/bin
Even if the paths look unusual, they both are correct - the first for a target and the second
for a native recipe. These paths are a consequence of the DESTDIR mechanism and while they
appear strange, they are correct and in practice very effective.
14.25.The files provided by my -native recipe do not appear to be available to other recipes. Files
are missing from the native sysroot, my recipe is installing to the wrong place, or I am getting
permissions errors during the do_install task in my recipe! What is wrong?
This situation results when a build system does not recognize the environment
variables supplied to it by BitBake [http://www.yoctoproject.org/docs/1.8/dev-manual/devmanual.html#bitbake-term]. The incident that prompted this FAQ entry involved a Makefile that
used an environment variable named BINDIR instead of the more standard variable bindir. The
makefile's hardcoded default value of "/usr/bin" worked most of the time, but not for the recipe's
-native variant. For another example, permissions errors might be caused by a Makefile that
ignores DESTDIR or uses a different name for that environment variable. Check the the build
system to see if these kinds of issues exist.

223

Chapter 15. Contributing to the
Yocto Project
15.1. Introduction
The Yocto Project team is happy for people to experiment with the Yocto Project. A number of
places exist to find help if you run into difficulties or find bugs. To find out how to download
source code, see the "Yocto Project Release [http://www.yoctoproject.org/docs/1.8/dev-manual/devmanual.html#local-yp-release]" section in the Yocto Project Development Manual.

15.2. Tracking Bugs
If you find problems with the Yocto Project, you should report them using the Bugzilla application at
http://bugzilla.yoctoproject.org.

15.3. Mailing lists
A number of mailing lists maintained by the Yocto Project exist as well as related OpenEmbedded
mailing lists for discussion, patch submission and announcements. To subscribe to one of the following
mailing lists, click on the appropriate URL in the following list and follow the instructions:
• http://lists.yoctoproject.org/listinfo/yocto - General Yocto Project discussion mailing list.
• http://lists.openembedded.org/mailman/listinfo/openembedded-core - Discussion mailing list about
OpenEmbedded-Core (the core metadata).
• http://lists.openembedded.org/mailman/listinfo/openembedded-devel - Discussion mailing list
about OpenEmbedded.
• http://lists.openembedded.org/mailman/listinfo/bitbake-devel - Discussion mailing list about the
BitBake [http://www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#bitbake-term] build
tool.
• http://lists.yoctoproject.org/listinfo/poky - Discussion mailing list
www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#poky].

about

Poky

[http://

• http://lists.yoctoproject.org/listinfo/yocto-announce - Mailing list to receive official Yocto Project
release and milestone announcements.
For more Yocto Project-related mailing lists, see the Yocto Project community mailing lists page here
[http://www.yoctoproject.org/tools-resources/community/mailing-lists].

15.4. Internet Relay Chat (IRC)
Two IRC channels on freenode are available for the Yocto Project and Poky discussions:
• #yocto
• #poky

15.5. Links
Here is a list of resources you will find helpful:
• The Yocto Project website [http://www.yoctoproject.org]: The home site for the Yocto Project.
• Intel Corporation [http://www.intel.com/]: The company that acquired OpenedHand in 2008 and
began development on the Yocto Project.

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Contributing to the Yocto Project

• OpenEmbedded [http://www.openembedded.org]: The upstream, generic, embedded distribution
used as the basis for the build system in the Yocto Project. Poky derives from and contributes back
to the OpenEmbedded project.
• BitBake [http://www.openembedded.org/wiki/BitBake]: The tool used to process metadata.
• BitBake User Manual [http://www.yoctoproject.org/docs/1.8/bitbake-user-manual/bitbake-usermanual.html]: A comprehensive guide to the BitBake tool. In the Source Directory [http://
www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#source-directory], you can find the
BitBake User Manual in the bitbake/doc/bitbake-user-manual directory.
• QEMU [http://wiki.qemu.org/Index.html]: An open source machine emulator and virtualizer.

15.6. Contributions
The Yocto Project gladly accepts contributions. You can submit changes to the project either by
creating and sending pull requests, or by submitting patches through email. For information on how
to do both as well as information on how to identify the maintainer for each area of code, see the
"How to Submit a Change [http://www.yoctoproject.org/docs/1.8/dev-manual/dev-manual.html#howto-submit-a-change]" section in the Yocto Project Development Manual.

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