Oracle VM VirtualBox User Manual

UserManual

User Manual:

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Oracle VM
VirtualBox R
User Manual
Version 4.3.18
c 2004-2014 Oracle Corporation
http://www.virtualbox.org

Contents
1 First steps
1.1
Why is virtualization useful? . . . . . . . . . . . . . . .
1.2
Some terminology . . . . . . . . . . . . . . . . . . . . .
1.3
Features overview . . . . . . . . . . . . . . . . . . . . .
1.4
Supported host operating systems . . . . . . . . . . . .
1.5
Installing VirtualBox and extension packs . . . . . . . .
1.6
Starting VirtualBox . . . . . . . . . . . . . . . . . . . .
1.7
Creating your first virtual machine . . . . . . . . . . .
1.8
Running your virtual machine . . . . . . . . . . . . . .
1.8.1
Starting a new VM for the first time . . . . . .
1.8.2
Capturing and releasing keyboard and mouse
1.8.3
Typing special characters . . . . . . . . . . . .
1.8.4
Changing removable media . . . . . . . . . . .
1.8.5
Resizing the machine’s window . . . . . . . .
1.8.6
Saving the state of the machine . . . . . . . .
1.9
Using VM groups . . . . . . . . . . . . . . . . . . . . .
1.10 Snapshots . . . . . . . . . . . . . . . . . . . . . . . . .
1.10.1 Taking, restoring and deleting snapshots . . .
1.10.2 Snapshot contents . . . . . . . . . . . . . . . .
1.11 Virtual machine configuration . . . . . . . . . . . . . .
1.12 Removing virtual machines . . . . . . . . . . . . . . . .
1.13 Cloning virtual machines . . . . . . . . . . . . . . . . .
1.14 Importing and exporting virtual machines . . . . . . .
1.15 Global Settings . . . . . . . . . . . . . . . . . . . . . .
1.16 Alternative front-ends . . . . . . . . . . . . . . . . . . .

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2 Installation details
2.1
Installing on Windows hosts . . . . . .
2.1.1
Prerequisites . . . . . . . . . .
2.1.2
Performing the installation . .
2.1.3
Uninstallation . . . . . . . . .
2.1.4
Unattended installation . . . .
2.2
Installing on Mac OS X hosts . . . . . .
2.2.1
Performing the installation . .
2.2.2
Uninstallation . . . . . . . . .
2.2.3
Unattended installation . . . .
2.3
Installing on Linux hosts . . . . . . . .
2.3.1
Prerequisites . . . . . . . . . .
2.3.2
The VirtualBox kernel module
2.3.3
Performing the installation . .
2.3.4
The vboxusers group . . . . .
2.3.5
Starting VirtualBox on Linux .
2.4
Installing on Solaris hosts . . . . . . .
2.4.1
Performing the installation . .
2.4.2
The vboxuser group . . . . . .
2.4.3
Starting VirtualBox on Solaris

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Contents
2.4.4
2.4.5
2.4.6

Uninstallation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Unattended installation . . . . . . . . . . . . . . . . . . . . . . . . . . .
Configuring a zone for running VirtualBox . . . . . . . . . . . . . . . .

3 Configuring virtual machines
3.1
Supported guest operating systems . . . . . . . . . . . . . .
3.1.1
Mac OS X guests . . . . . . . . . . . . . . . . . . . .
3.1.2
64-bit guests . . . . . . . . . . . . . . . . . . . . . .
3.2
Emulated hardware . . . . . . . . . . . . . . . . . . . . . . .
3.3
General settings . . . . . . . . . . . . . . . . . . . . . . . . .
3.3.1
“Basic” tab . . . . . . . . . . . . . . . . . . . . . . .
3.3.2
“Advanced” tab . . . . . . . . . . . . . . . . . . . .
3.3.3
“Description” tab . . . . . . . . . . . . . . . . . . .
3.4
System settings . . . . . . . . . . . . . . . . . . . . . . . . .
3.4.1
“Motherboard” tab . . . . . . . . . . . . . . . . . .
3.4.2
“Processor” tab . . . . . . . . . . . . . . . . . . . .
3.4.3
“Acceleration” tab . . . . . . . . . . . . . . . . . . .
3.5
Display settings . . . . . . . . . . . . . . . . . . . . . . . . .
3.6
Storage settings . . . . . . . . . . . . . . . . . . . . . . . . .
3.7
Audio settings . . . . . . . . . . . . . . . . . . . . . . . . . .
3.8
Network settings . . . . . . . . . . . . . . . . . . . . . . . .
3.9
Serial ports . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.10 USB support . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.10.1 USB settings . . . . . . . . . . . . . . . . . . . . . .
3.10.2 Implementation notes for Windows and Linux hosts
3.11 Shared folders . . . . . . . . . . . . . . . . . . . . . . . . . .
3.12 Alternative firmware (EFI) . . . . . . . . . . . . . . . . . . .
3.12.1 Video modes in EFI . . . . . . . . . . . . . . . . . .
3.12.2 Specifying boot arguments . . . . . . . . . . . . . .

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4 Guest Additions
4.1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.2
Installing and Maintaining Guest Additions . . . . . . . . . . . .
4.2.1
Guest Additions for Windows . . . . . . . . . . . . . . .
4.2.2
Guest Additions for Linux . . . . . . . . . . . . . . . . .
4.2.3
Guest Additions for Solaris . . . . . . . . . . . . . . . .
4.2.4
Guest Additions for OS/2 . . . . . . . . . . . . . . . . .
4.3
Shared folders . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.3.1
Manual mounting . . . . . . . . . . . . . . . . . . . . .
4.3.2
Automatic mounting . . . . . . . . . . . . . . . . . . .
4.4
Hardware-accelerated graphics . . . . . . . . . . . . . . . . . .
4.4.1
Hardware 3D acceleration (OpenGL and Direct3D 8/9)
4.4.2
Hardware 2D video acceleration for Windows guests . .
4.5
Seamless windows . . . . . . . . . . . . . . . . . . . . . . . . .
4.6
Guest properties . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.7
Guest control . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.8
Memory overcommitment . . . . . . . . . . . . . . . . . . . . .
4.8.1
Memory ballooning . . . . . . . . . . . . . . . . . . . .
4.8.2
Page Fusion . . . . . . . . . . . . . . . . . . . . . . . .

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5 Virtual storage
5.1
Hard disk controllers: IDE, SATA (AHCI), SCSI, SAS . . . . . . . . . . . . . . . .
5.2
Disk image files (VDI, VMDK, VHD, HDD) . . . . . . . . . . . . . . . . . . . . .
5.3
The Virtual Media Manager . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Contents
5.4
5.5
5.6
5.7
5.8
5.9
5.10

Special image write modes . . . . .
Differencing images . . . . . . . . .
Cloning disk images . . . . . . . . .
Host I/O caching . . . . . . . . . .
Limiting bandwidth for disk images
CD/DVD support . . . . . . . . . .
iSCSI servers . . . . . . . . . . . . .

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6 Virtual networking
6.1
Virtual networking hardware . . . . . . . . . . . . . .
6.2
Introduction to networking modes . . . . . . . . . . .
6.3
Network Address Translation (NAT) . . . . . . . . . .
6.3.1
Configuring port forwarding with NAT . . .
6.3.2
PXE booting with NAT . . . . . . . . . . . . .
6.3.3
NAT limitations . . . . . . . . . . . . . . . .
6.4
Network Address Translation Service (experimental)
6.5
Bridged networking . . . . . . . . . . . . . . . . . . .
6.6
Internal networking . . . . . . . . . . . . . . . . . . .
6.7
Host-only networking . . . . . . . . . . . . . . . . . .
6.8
UDP Tunnel networking . . . . . . . . . . . . . . . .
6.9
VDE networking . . . . . . . . . . . . . . . . . . . . .
6.10 Limiting bandwidth for network I/O . . . . . . . . . .
6.11 Improving network performance . . . . . . . . . . . .

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7 Remote virtual machines
7.1
Remote display (VRDP support) . . . . . . . . . . . . . . . . . . . . .
7.1.1
Common third-party RDP viewers . . . . . . . . . . . . . . .
7.1.2
VBoxHeadless, the remote desktop server . . . . . . . . . . .
7.1.3
Step by step: creating a virtual machine on a headless server
7.1.4
Remote USB . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.1.5
RDP authentication . . . . . . . . . . . . . . . . . . . . . . .
7.1.6
RDP encryption . . . . . . . . . . . . . . . . . . . . . . . . .
7.1.7
Multiple connections to the VRDP server . . . . . . . . . . .
7.1.8
Multiple remote monitors . . . . . . . . . . . . . . . . . . . .
7.1.9
VRDP video redirection . . . . . . . . . . . . . . . . . . . . .
7.1.10 VRDP customization . . . . . . . . . . . . . . . . . . . . . . .
7.2
Teleporting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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8 VBoxManage
8.1
Introduction . . . . . . . . . . . . . . . . . . . . . . . .
8.2
Commands overview . . . . . . . . . . . . . . . . . . .
8.3
General options . . . . . . . . . . . . . . . . . . . . . .
8.4
VBoxManage list . . . . . . . . . . . . . . . . . . . . .
8.5
VBoxManage showvminfo . . . . . . . . . . . . . . . .
8.6
VBoxManage registervm / unregistervm . . . . . . . .
8.7
VBoxManage createvm . . . . . . . . . . . . . . . . . .
8.8
VBoxManage modifyvm . . . . . . . . . . . . . . . . .
8.8.1
General settings . . . . . . . . . . . . . . . . .
8.8.2
Networking settings . . . . . . . . . . . . . . .
8.8.3
Serial port, audio, clipboard and USB settings
8.8.4
Remote machine settings . . . . . . . . . . . .
8.8.5
Teleporting settings . . . . . . . . . . . . . . .
8.9
VBoxManage clonevm . . . . . . . . . . . . . . . . . .
8.10 VBoxManage import . . . . . . . . . . . . . . . . . . .

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Contents
8.11
8.12
8.13
8.14
8.15
8.16
8.17
8.18
8.19
8.20
8.21
8.22
8.23
8.24
8.25
8.26
8.27
8.28
8.29
8.30
8.31
8.32
8.33
8.34
8.35
8.36

VBoxManage export . . . . . . . . . . . . .
VBoxManage startvm . . . . . . . . . . . .
VBoxManage controlvm . . . . . . . . . .
VBoxManage discardstate . . . . . . . . .
VBoxManage adoptstate . . . . . . . . . .
VBoxManage snapshot . . . . . . . . . . .
VBoxManage closemedium . . . . . . . . .
VBoxManage storageattach . . . . . . . . .
VBoxManage storagectl . . . . . . . . . . .
VBoxManage bandwidthctl . . . . . . . . .
VBoxManage showhdinfo . . . . . . . . . .
VBoxManage createhd . . . . . . . . . . .
VBoxManage modifyhd . . . . . . . . . . .
VBoxManage clonehd . . . . . . . . . . . .
VBoxManage convertfromraw . . . . . . .
VBoxManage getextradata/setextradata . .
VBoxManage setproperty . . . . . . . . . .
VBoxManage usbfilter add/modify/remove
VBoxManage sharedfolder add/remove . .
VBoxManage guestproperty . . . . . . . .
VBoxManage guestcontrol . . . . . . . . .
VBoxManage debugvm . . . . . . . . . . .
VBoxManage metrics . . . . . . . . . . . .
VBoxManage hostonlyif . . . . . . . . . . .
VBoxManage dhcpserver . . . . . . . . . .
VBoxManage extpack . . . . . . . . . . . .

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9 Advanced topics
9.1
VBoxSDL, the simplified VM displayer . . . . . . . . . . . . . . . . . . . . .
9.1.1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.1.2
Secure labeling with VBoxSDL . . . . . . . . . . . . . . . . . . . .
9.1.3
Releasing modifiers with VBoxSDL on Linux . . . . . . . . . . . .
9.2
Automated guest logons . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.2.1
Automated Windows guest logons . . . . . . . . . . . . . . . . . .
9.2.2
Automated Linux/Unix guest logons . . . . . . . . . . . . . . . . .
9.3
Advanced configuration for Windows guests . . . . . . . . . . . . . . . . .
9.3.1
Automated Windows system preparation . . . . . . . . . . . . . .
9.4
Advanced configuration for Linux and Solaris guests . . . . . . . . . . . . .
9.4.1
Manual setup of selected guest services on Linux . . . . . . . . . .
9.4.2
Guest graphics and mouse driver setup in depth . . . . . . . . . .
9.5
CPU hot-plugging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.6
PCI passthrough . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.7
Webcam passthrough . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.7.1
Using a host webcam in the guest . . . . . . . . . . . . . . . . . .
9.7.2
Windows hosts . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.7.3
Mac OS X hosts . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.7.4
Linux hosts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.8
Advanced display configuration . . . . . . . . . . . . . . . . . . . . . . . .
9.8.1
Custom VESA resolutions . . . . . . . . . . . . . . . . . . . . . . .
9.8.2
Configuring the maximum resolution of guests when using the
graphical frontend . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.9
Advanced storage configuration . . . . . . . . . . . . . . . . . . . . . . . .
9.9.1
Using a raw host hard disk from a guest . . . . . . . . . . . . . . .
9.9.2
Configuring the hard disk vendor product data (VPD) . . . . . . .

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Contents
9.9.3
Access iSCSI targets via Internal Networking . . . . . . . . . . . . . .
9.10 Legacy commands for using serial ports . . . . . . . . . . . . . . . . . . . . . .
9.11 Fine-tuning the VirtualBox NAT engine . . . . . . . . . . . . . . . . . . . . . .
9.11.1 Configuring the address of a NAT network interface . . . . . . . . . .
9.11.2 Configuring the boot server (next server) of a NAT network interface .
9.11.3 Tuning TCP/IP buffers for NAT . . . . . . . . . . . . . . . . . . . . . .
9.11.4 Binding NAT sockets to a specific interface . . . . . . . . . . . . . . .
9.11.5 Enabling DNS proxy in NAT mode . . . . . . . . . . . . . . . . . . . .
9.11.6 Using the host’s resolver as a DNS proxy in NAT mode . . . . . . . . .
9.11.7 Configuring aliasing of the NAT engine . . . . . . . . . . . . . . . . .
9.12 Configuring the BIOS DMI information . . . . . . . . . . . . . . . . . . . . . .
9.12.1 DMI BIOS information (type 0) . . . . . . . . . . . . . . . . . . . . .
9.12.2 DMI system information (type 1) . . . . . . . . . . . . . . . . . . . .
9.12.3 DMI board information (type 2) . . . . . . . . . . . . . . . . . . . . .
9.12.4 DMI system enclosure or chassis (type 3) . . . . . . . . . . . . . . . .
9.12.5 DMI processor informatiion (type 4) . . . . . . . . . . . . . . . . . . .
9.12.6 DMI OEM strings (type 11) . . . . . . . . . . . . . . . . . . . . . . . .
9.13 Configuring the custom ACPI table . . . . . . . . . . . . . . . . . . . . . . . .
9.14 Fine-tuning timers and time synchronization . . . . . . . . . . . . . . . . . . .
9.14.1 Configuring the guest time stamp counter (TSC) to reflect guest
execution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.14.2 Accelerate or slow down the guest clock . . . . . . . . . . . . . . . . .
9.14.3 Tuning the Guest Additions time synchronization parameters . . . . .
9.14.4 Disabling the Guest Additions time synchronization . . . . . . . . . .
9.15 Installing the alternate bridged networking driver on Solaris 11 hosts . . . . .
9.16 VirtualBox VNIC templates for VLANs on Solaris 11 hosts . . . . . . . . . . . .
9.17 Configuring multiple host-only network interfaces on Solaris hosts . . . . . . .
9.18 Configuring the VirtualBox CoreDumper on Solaris hosts . . . . . . . . . . . .
9.19 Locking down the VirtualBox manager GUI . . . . . . . . . . . . . . . . . . . .
9.19.1 Customizing the VM manager . . . . . . . . . . . . . . . . . . . . . .
9.19.2 VM selector customization . . . . . . . . . . . . . . . . . . . . . . . .
9.19.3 Configure VM selector menu entries . . . . . . . . . . . . . . . . . . .
9.19.4 Configure VM window menu entries . . . . . . . . . . . . . . . . . . .
9.19.5 Configure VM window status bar entries . . . . . . . . . . . . . . . .
9.19.6 Configure VM window visual modes . . . . . . . . . . . . . . . . . . .
9.19.7 Host Key customization . . . . . . . . . . . . . . . . . . . . . . . . . .
9.19.8 Action when terminating the VM . . . . . . . . . . . . . . . . . . . . .
9.19.9 Action for handling a Guru Meditation . . . . . . . . . . . . . . . . .
9.19.10 Configuring automatic mouse capturing . . . . . . . . . . . . . . . . .
9.19.11 Requesting legacy full-screen mode . . . . . . . . . . . . . . . . . . .
9.20 Starting the VirtualBox web service automatically . . . . . . . . . . . . . . . .
9.20.1 Linux: starting the webservice via init . . . . . . . . . . . . . . . . .
9.20.2 Solaris: starting the web service via SMF . . . . . . . . . . . . . . . .
9.20.3 Mac OS X: starting the webservice via launchd . . . . . . . . . . . . .
9.21 VirtualBox Watchdog . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.21.1 Memory ballooning control . . . . . . . . . . . . . . . . . . . . . . . .
9.21.2 Host isolation detection . . . . . . . . . . . . . . . . . . . . . . . . . .
9.21.3 More information . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.21.4 Linux: starting the watchdog service via init . . . . . . . . . . . . .
9.21.5 Solaris: starting the watchdog service via SMF . . . . . . . . . . . . .
9.22 Other extension packs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.23 Starting virtual machines during system boot . . . . . . . . . . . . . . . . . . .
9.23.1 Linux: starting the autostart service via init . . . . . . . . . . . . . .

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9.24
9.25
9.26
9.27

9.23.2 Solaris: starting the autostart service via SMF . . . . . . . . .
9.23.3 Mac OS X: starting the autostart service via launchd . . . . . .
VirtualBox expert storage management . . . . . . . . . . . . . . . . . .
Handling of host power management events . . . . . . . . . . . . . . .
Experimental support for passing through SSE4.1 / SSE4.2 instructions
Support for keyboard indicators synchronization . . . . . . . . . . . . .

10 Technical background
10.1 Where VirtualBox stores its files . . . . . . . . . . . . . . . .
10.1.1 Machines created by VirtualBox version 4.0 or later
10.1.2 Machines created by VirtualBox versions before 4.0
10.1.3 Global configuration data . . . . . . . . . . . . . . .
10.1.4 Summary of 4.0 configuration changes . . . . . . .
10.1.5 VirtualBox XML files . . . . . . . . . . . . . . . . . .
10.2 VirtualBox executables and components . . . . . . . . . . .
10.3 Hardware vs. software virtualization . . . . . . . . . . . . .
10.4 Details about software virtualization . . . . . . . . . . . . .
10.5 Details about hardware virtualization . . . . . . . . . . . . .
10.6 Nested paging and VPIDs . . . . . . . . . . . . . . . . . . . .

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11 VirtualBox programming interfaces

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12 Troubleshooting
12.1 Procedures and tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.1.1 Categorizing and isolating problems . . . . . . . . . . . . . . . . . .
12.1.2 Collecting debugging information . . . . . . . . . . . . . . . . . . .
12.1.3 The built-in VM debugger . . . . . . . . . . . . . . . . . . . . . . . .
12.1.4 VM core format . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.2 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.2.1 Guest shows IDE/SATA errors for file-based images on slow host
file system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.2.2 Responding to guest IDE/SATA flush requests . . . . . . . . . . . . .
12.2.3 Poor performance caused by host power management . . . . . . . .
12.2.4 GUI: 2D Video Acceleration option is grayed out . . . . . . . . . . .
12.3 Windows guests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.3.1 Windows bluescreens after changing VM configuration . . . . . . .
12.3.2 Windows 0x101 bluescreens with SMP enabled (IPI timeout) . . . .
12.3.3 Windows 2000 installation failures . . . . . . . . . . . . . . . . . .
12.3.4 How to record bluescreen information from Windows guests . . . .
12.3.5 No networking in Windows Vista guests . . . . . . . . . . . . . . . .
12.3.6 Windows guests may cause a high CPU load . . . . . . . . . . . . .
12.3.7 Long delays when accessing shared folders . . . . . . . . . . . . . .
12.3.8 USB tablet coordinates wrong in Windows 98 guests . . . . . . . . .
12.3.9 Windows guests are removed from an Active Directory domain
after restoring a snapshot . . . . . . . . . . . . . . . . . . . . . . . .
12.3.10 Restoring d3d8.dll and d3d9.dll . . . . . . . . . . . . . . . . . . . .
12.4 Linux and X11 guests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.4.1 Linux guests may cause a high CPU load . . . . . . . . . . . . . . .
12.4.2 AMD Barcelona CPUs . . . . . . . . . . . . . . . . . . . . . . . . . .
12.4.3 Buggy Linux 2.6 kernel versions . . . . . . . . . . . . . . . . . . . .
12.4.4 Shared clipboard, auto-resizing and seamless desktop in X11 guests
12.5 Solaris guests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.5.1 Older Solaris 10 releases hang in 64-bit mode . . . . . . . . . . . .
12.6 Windows hosts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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12.6.1 VBoxSVC out-of-process COM server issues . . . . . . . . .
12.6.2 CD/DVD changes not recognized . . . . . . . . . . . . . . .
12.6.3 Sluggish response when using Microsoft RDP client . . . .
12.6.4 Running an iSCSI initiator and target on a single system . .
12.6.5 Bridged networking adapters missing . . . . . . . . . . . .
12.6.6 Host-only networking adapters cannot be created . . . . .
12.7 Linux hosts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.7.1 Linux kernel module refuses to load . . . . . . . . . . . . .
12.7.2 Linux host CD/DVD drive not found . . . . . . . . . . . . .
12.7.3 Linux host CD/DVD drive not found (older distributions) .
12.7.4 Linux host floppy not found . . . . . . . . . . . . . . . . .
12.7.5 Strange guest IDE error messages when writing to CD/DVD
12.7.6 VBoxSVC IPC issues . . . . . . . . . . . . . . . . . . . . . .
12.7.7 USB not working . . . . . . . . . . . . . . . . . . . . . . .
12.7.8 PAX/grsec kernels . . . . . . . . . . . . . . . . . . . . . . .
12.7.9 Linux kernel vmalloc pool exhausted . . . . . . . . . . . .
12.8 Solaris hosts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.8.1 Cannot start VM, not enough contiguous memory . . . . .
12.8.2 VM aborts with out of memory errors on Solaris 10 hosts .
13 Security guide
13.1 Overview . . . . . . . . . . . . . . . . . . . . . . .
13.1.1 General Security Principles . . . . . . . .
13.2 Secure Installation and Configuration . . . . . . .
13.2.1 Installation Overview . . . . . . . . . . .
13.2.2 Post Installation Configuration . . . . . .
13.3 Security Features . . . . . . . . . . . . . . . . . .
13.3.1 The Security Model . . . . . . . . . . . .
13.3.2 Secure Configuration of Virtual Machines
13.3.3 Configuring and Using Authentication . .
13.3.4 Potentially insecure operations . . . . . .
13.3.5 Encryption . . . . . . . . . . . . . . . . .

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14 Known limitations
229
14.1 Experimental Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229
14.2 Known Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229
15 Change log
15.1 Version 4.3.18 (2014-10-10)
15.2 Version 4.3.16 (2014-09-09)
15.3 Version 4.3.14 (2014-07-15)
15.4 Version 4.3.12 (2014-05-16)
15.5 Version 4.3.10 (2014-03-26)
15.6 Version 4.3.8 (2014-02-25) .
15.7 Version 4.3.6 (2013-12-18) .
15.8 Version 4.3.4 (2013-11-29) .
15.9 Version 4.3.2 (2013-11-01) .
15.10 Version 4.3.0 (2013-10-15) .
15.11 Version 4.2.22 (2014-01-10)
15.12 Version 4.2.20 (2013-11-28)
15.13 Version 4.2.18 (2013-09-06)
15.14 Version 4.2.16 (2013-07-04)
15.15 Version 4.2.14 (2013-06-21)
15.16 Version 4.2.12 (2013-04-12)

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15.17
15.18
15.19
15.20
15.21
15.22
15.23
15.24
15.25
15.26
15.27
15.28
15.29
15.30
15.31
15.32
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15.56
15.57
15.58
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15.60
15.61
15.62
15.63
15.64
15.65
15.66
15.67
15.68
15.69

Version 4.2.10 (2013-03-05)
Version 4.2.8 (2013-02-20) .
Version 4.2.6 (2012-12-19) .
Version 4.2.4 (2012-10-26) .
Version 4.2.2 (2012-10-18) .
Version 4.2.0 (2012-09-13) .
Version 4.1.18 (2012-06-06)
Version 4.1.16 (2012-05-22)
Version 4.1.14 (2012-04-13)
Version 4.1.12 (2012-04-03)
Version 4.1.10 (2012-03-13)
Version 4.1.8 (2011-12-19) .
Version 4.1.6 (2011-11-04) .
Version 4.1.4 (2011-10-03) .
Version 4.1.2 (2011-08-15) .
Version 4.1.0 (2011-07-19) .
Version 4.0.14 (2011-10-13)
Version 4.0.12 (2011-07-15)
Version 4.0.10 (2011-06-22)
Version 4.0.8 (2011-05-16) .
Version 4.0.6 (2011-04-21) .
Version 4.0.4 (2011-02-17) .
Version 4.0.2 (2011-01-18) .
Version 4.0.0 (2010-12-22) .
Version 3.2.12 (2010-11-30)
Version 3.2.10 (2010-10-08)
Version 3.2.8 (2010-08-05) .
Version 3.2.6 (2010-06-25) .
Version 3.2.4 (2010-06-07) .
Version 3.2.2 (2010-06-02) .
Version 3.2.0 (2010-05-18) .
Version 3.1.8 (2010-05-10) .
Version 3.1.6 (2010-03-25) .
Version 3.1.4 (2010-02-12) .
Version 3.1.2 (2009-12-17) .
Version 3.1.0 (2009-11-30) .
Version 3.0.12 (2009-11-10)
Version 3.0.10 (2009-10-29)
Version 3.0.8 (2009-10-02) .
Version 3.0.6 (2009-09-09) .
Version 3.0.4 (2009-08-04) .
Version 3.0.2 (2009-07-10) .
Version 3.0.0 (2009-06-30) .
Version 2.2.4 (2009-05-29) .
Version 2.2.2 (2009-04-27) .
Version 2.2.0 (2009-04-08) .
Version 2.1.4 (2009-02-16) .
Version 2.1.2 (2009-01-21) .
Version 2.1.0 (2008-12-17) .
Version 2.0.8 (2009-03-10) .
Version 2.0.6 (2008-11-21) .
Version 2.0.4 (2008-10-24) .
Version 2.0.2 (2008-09-12) .

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15.70 Version 2.0.0 (2008-09-04) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 326
16 Third-party materials and licenses
16.1 Materials . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.2 Licenses . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.2.1 GNU General Public License (GPL) . . . . . . . .
16.2.2 GNU Lesser General Public License (LGPL) . . .
16.2.3 Mozilla Public License (MPL) . . . . . . . . . . .
16.2.4 MIT License . . . . . . . . . . . . . . . . . . . .
16.2.5 X Consortium License (X11) . . . . . . . . . . .
16.2.6 zlib license . . . . . . . . . . . . . . . . . . . . .
16.2.7 OpenSSL license . . . . . . . . . . . . . . . . . .
16.2.8 Slirp license . . . . . . . . . . . . . . . . . . . .
16.2.9 liblzf license . . . . . . . . . . . . . . . . . . . .
16.2.10 libpng license . . . . . . . . . . . . . . . . . . .
16.2.11 lwIP license . . . . . . . . . . . . . . . . . . . .
16.2.12 libxml license . . . . . . . . . . . . . . . . . . .
16.2.13 libxslt licenses . . . . . . . . . . . . . . . . . . .
16.2.14 gSOAP Public License Version 1.3a . . . . . . . .
16.2.15 Chromium licenses . . . . . . . . . . . . . . . .
16.2.16 curl license . . . . . . . . . . . . . . . . . . . . .
16.2.17 libgd license . . . . . . . . . . . . . . . . . . . .
16.2.18 BSD license from Intel . . . . . . . . . . . . . .
16.2.19 libjpeg License . . . . . . . . . . . . . . . . . . .
16.2.20 x86 SIMD extension for IJG JPEG library license
16.2.21 FreeBSD license . . . . . . . . . . . . . . . . . .
16.2.22 NetBSD license . . . . . . . . . . . . . . . . . .
16.2.23 PCRE license . . . . . . . . . . . . . . . . . . . .
16.2.24 libffi license . . . . . . . . . . . . . . . . . . . .
16.2.25 FLTK license . . . . . . . . . . . . . . . . . . . .
16.2.26 Expat license . . . . . . . . . . . . . . . . . . . .
16.2.27 Fontconfig license . . . . . . . . . . . . . . . . .
16.2.28 Freetype license . . . . . . . . . . . . . . . . . .
16.2.29 VPX License . . . . . . . . . . . . . . . . . . . .

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17 VirtualBox privacy information

365

Glossary

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1 First steps
Welcome to Oracle VM VirtualBox!
VirtualBox is a cross-platform virtualization application. What does that mean? For one thing,
it installs on your existing Intel or AMD-based computers, whether they are running Windows,
Mac, Linux or Solaris operating systems. Secondly, it extends the capabilities of your existing
computer so that it can run multiple operating systems (inside multiple virtual machines) at the
same time. So, for example, you can run Windows and Linux on your Mac, run Windows Server
2008 on your Linux server, run Linux on your Windows PC, and so on, all alongside your existing
applications. You can install and run as many virtual machines as you like – the only practical
limits are disk space and memory.
VirtualBox is deceptively simple yet also very powerful. It can run everywhere from small
embedded systems or desktop class machines all the way up to datacenter deployments and
even Cloud environments.
The following screenshot shows you how VirtualBox, installed on a Mac computer, is running
Windows 7 in a virtual machine window:

In this User Manual, we’ll begin simply with a quick introduction to virtualization and how to
get your first virtual machine running with the easy-to-use VirtualBox graphical user interface.
Subsequent chapters will go into much more detail covering more powerful tools and features,
but fortunately, it is not necessary to read the entire User Manual before you can use VirtualBox.
You can find a summary of VirtualBox’s capabilities in chapter 1.3, Features overview, page 13.
For existing VirtualBox users who just want to see what’s new in this release, there is a detailed
list in chapter 15, Change log, page 232.

1 First steps

1.1 Why is virtualization useful?
The techniques and features that VirtualBox provides are useful for several scenarios:
• Running multiple operating systems simultaneously. VirtualBox allows you to run more
than one operating system at a time. This way, you can run software written for one
operating system on another (for example, Windows software on Linux or a Mac) without
having to reboot to use it. Since you can configure what kinds of “virtual” hardware should
be presented to each such operating system, you can install an old operating system such
as DOS or OS/2 even if your real computer’s hardware is no longer supported by that
operating system.
• Easier software installations. Software vendors can use virtual machines to ship entire
software configurations. For example, installing a complete mail server solution on a real
machine can be a tedious task. With VirtualBox, such a complex setup (then often called
an “appliance”) can be packed into a virtual machine. Installing and running a mail server
becomes as easy as importing such an appliance into VirtualBox.
• Testing and disaster recovery. Once installed, a virtual machine and its virtual hard disks
can be considered a “container” that can be arbitrarily frozen, woken up, copied, backed
up, and transported between hosts.
On top of that, with the use of another VirtualBox feature called “snapshots”, one can save
a particular state of a virtual machine and revert back to that state, if necessary. This way,
one can freely experiment with a computing environment. If something goes wrong (e.g.
after installing misbehaving software or infecting the guest with a virus), one can easily
switch back to a previous snapshot and avoid the need of frequent backups and restores.
Any number of snapshots can be created, allowing you to travel back and forward in virtual
machine time. You can delete snapshots while a VM is running to reclaim disk space.
• Infrastructure consolidation. Virtualization can significantly reduce hardware and electricity costs. Most of the time, computers today only use a fraction of their potential power
and run with low average system loads. A lot of hardware resources as well as electricity
is thereby wasted. So, instead of running many such physical computers that are only partially used, one can pack many virtual machines onto a few powerful hosts and balance the
loads between them.

1.2 Some terminology
When dealing with virtualization (and also for understanding the following chapters of this
documentation), it helps to acquaint oneself with a bit of crucial terminology, especially the
following terms:
Host operating system (host OS). This is the operating system of the physical computer on
which VirtualBox was installed. There are versions of VirtualBox for Windows, Mac OS
X, Linux and Solaris hosts; for details, please see chapter 1.4, Supported host operating
systems, page 15.
Most of the time, this User Manual discusses all VirtualBox versions together. There may
be platform-specific differences which we will point out where appropriate.
Guest operating system (guest OS). This is the operating system that is running inside the
virtual machine. Theoretically, VirtualBox can run any x86 operating system (DOS, Windows, OS/2, FreeBSD, OpenBSD), but to achieve near-native performance of the guest
code on your machine, we had to go through a lot of optimizations that are specific to
certain operating systems. So while your favorite operating system may run as a guest, we

1 First steps
officially support and optimize for a select few (which, however, include the most common
ones).
See chapter 3.1, Supported guest operating systems, page 45 for details.
Virtual machine (VM). This is the special environment that VirtualBox creates for your guest
operating system while it is running. In other words, you run your guest operating system
“in” a VM. Normally, a VM will be shown as a window on your computer’s desktop, but
depending on which of the various frontends of VirtualBox you use, it can be displayed in
full screen mode or remotely on another computer.
In a more abstract way, internally, VirtualBox thinks of a VM as a set of parameters that
determine its behavior. They include hardware settings (how much memory the VM should
have, what hard disks VirtualBox should virtualize through which container files, what CDs
are mounted etc.) as well as state information (whether the VM is currently running, saved,
its snapshots etc.). These settings are mirrored in the VirtualBox Manager window as well
as the VBoxManage command line program; see chapter 8, VBoxManage, page 113. In other
words, a VM is also what you can see in its settings dialog.
Guest Additions. This refers to special software packages which are shipped with VirtualBox
but designed to be installed inside a VM to improve performance of the guest OS and to
add extra features. This is described in detail in chapter 4, Guest Additions, page 60.

1.3 Features overview
Here’s a brief outline of VirtualBox’s main features:
• Portability. VirtualBox runs on a large number of 32-bit and 64-bit host operating systems
(again, see chapter 1.4, Supported host operating systems, page 15 for details).
VirtualBox is a so-called “hosted” hypervisor (sometimes referred to as a “type 2” hypervisor). Whereas a “bare-metal” or “type 1” hypervisor would run directly on the hardware,
VirtualBox requires an existing operating system to be installed. It can thus run alongside
existing applications on that host.
To a very large degree, VirtualBox is functionally identical on all of the host platforms, and
the same file and image formats are used. This allows you to run virtual machines created
on one host on another host with a different host operating system; for example, you can
create a virtual machine on Windows and then run it under Linux.
In addition, virtual machines can easily be imported and exported using the Open Virtualization Format (OVF, see chapter 1.14, Importing and exporting virtual machines, page 31),
an industry standard created for this purpose. You can even import OVFs that were created
with a different virtualization software.
• No hardware virtualization required. For many scenarios, VirtualBox does not require
the processor features built into newer hardware like Intel VT-x or AMD-V. As opposed
to many other virtualization solutions, you can therefore use VirtualBox even on older
hardware where these features are not present. The technical details are explained in
chapter 10.3, Hardware vs. software virtualization, page 202.
• Guest Additions: shared folders, seamless windows, 3D virtualization. The VirtualBox
Guest Additions are software packages which can be installed inside of supported guest
systems to improve their performance and to provide additional integration and communication with the host system. After installing the Guest Additions, a virtual machine will support automatic adjustment of video resolutions, seamless windows, accelerated 3D graphics
and more. The Guest Additions are described in detail in chapter 4, Guest Additions, page
60.

1 First steps
In particular, Guest Additions provide for “shared folders”, which let you access files from
the host system from within a guest machine. Shared folders are described in chapter 4.3,
Shared folders, page 70.
• Great hardware support. Among others, VirtualBox supports:
– Guest multiprocessing (SMP). VirtualBox can present up to 32 virtual CPUs to each
virtual machine, irrespective of how many CPU cores are physically present on your
host.
– USB device support. VirtualBox implements a virtual USB controller and allows you
to connect arbitrary USB devices to your virtual machines without having to install
device-specific drivers on the host. USB support is not limited to certain device categories. For details, see chapter 3.10.1, USB settings, page 56.
– Hardware compatibility. VirtualBox virtualizes a vast array of virtual devices, among
them many devices that are typically provided by other virtualization platforms. That
includes IDE, SCSI and SATA hard disk controllers, several virtual network cards and
sound cards, virtual serial and parallel ports and an Input/Output Advanced Programmable Interrupt Controller (I/O APIC), which is found in many modern PC systems. This eases cloning of PC images from real machines and importing of third-party
virtual machines into VirtualBox.
– Full ACPI support. The Advanced Configuration and Power Interface (ACPI) is fully
supported by VirtualBox. This eases cloning of PC images from real machines or thirdparty virtual machines into VirtualBox. With its unique ACPI power status support,
VirtualBox can even report to ACPI-aware guest operating systems the power status
of the host. For mobile systems running on battery, the guest can thus enable energy
saving and notify the user of the remaining power (e.g. in full screen modes).
– Multiscreen resolutions. VirtualBox virtual machines support screen resolutions
many times that of a physical screen, allowing them to be spread over a large number
of screens attached to the host system.
– Built-in iSCSI support. This unique feature allows you to connect a virtual machine
directly to an iSCSI storage server without going through the host system. The VM
accesses the iSCSI target directly without the extra overhead that is required for virtualizing hard disks in container files. For details, see chapter 5.10, iSCSI servers, page
91.
– PXE Network boot. The integrated virtual network cards of VirtualBox fully support
remote booting via the Preboot Execution Environment (PXE).
• Multigeneration branched snapshots. VirtualBox can save arbitrary snapshots of the
state of the virtual machine. You can go back in time and revert the virtual machine to any
such snapshot and start an alternative VM configuration from there, effectively creating a
whole snapshot tree. For details, see chapter 1.10, Snapshots, page 27. You can create and
delete snapshots while the virtual machine is running.
• VM groups. VirtualBox provides a groups feature that enables the user to organize virtual
machines collectively, as well as individually. In addition to basic groups, it is also possible
for any VM to be in more than one group, and for groups to be nested in a hierarchy – i.e.
groups of groups. In general, the operations that can be performed on groups are the same
as those that can be applied to individual VMs i.e. Start, Pause, Reset, Close (Save state,
Send Shutdown, Poweroff), Discard Saved State, Show in fileSystem, Sort.
• Clean architecture; unprecedented modularity. VirtualBox has an extremely modular
design with well-defined internal programming interfaces and a clean separation of client
and server code. This makes it easy to control it from several interfaces at once: for
example, you can start a VM simply by clicking on a button in the VirtualBox graphical

1 First steps
user interface and then control that machine from the command line, or even remotely.
See chapter 1.16, Alternative front-ends, page 33 for details.
Due to its modular architecture, VirtualBox can also expose its full functionality and configurability through a comprehensive software development kit (SDK), which allows for
integrating every aspect of VirtualBox with other software systems. Please see chapter 11,
VirtualBox programming interfaces, page 208 for details.
• Remote machine display. The VirtualBox Remote Desktop Extension (VRDE) allows for
high-performance remote access to any running virtual machine. This extension supports
the Remote Desktop Protocol (RDP) originally built into Microsoft Windows, with special
additions for full client USB support.
The VRDE does not rely on the RDP server that is built into Microsoft Windows; instead, it
is plugged directly into the virtualization layer. As a result, it works with guest operating
systems other than Windows (even in text mode) and does not require application support
in the virtual machine either. The VRDE is described in detail in chapter 7.1, Remote display
(VRDP support), page 103.
On top of this special capacity, VirtualBox offers you more unique features:
– Extensible RDP authentication. VirtualBox already supports Winlogon on Windows
and PAM on Linux for RDP authentication. In addition, it includes an easy-to-use SDK
which allows you to create arbitrary interfaces for other methods of authentication;
see chapter 7.1.5, RDP authentication, page 107 for details.
– USB over RDP. Via RDP virtual channel support, VirtualBox also allows you to connect
arbitrary USB devices locally to a virtual machine which is running remotely on a
VirtualBox RDP server; see chapter 7.1.4, Remote USB, page 107 for details.

1.4 Supported host operating systems
Currently, VirtualBox runs on the following host operating systems:
• Windows hosts:
– Windows XP, all service packs (32-bit)
– Windows Server 2003 (32-bit)
– Windows Vista (32-bit and 64-bit1 ).
– Windows Server 2008 (32-bit and 64-bit)
– Windows 7 (32-bit and 64-bit)
– Windows 8 (32-bit and 64-bit)
– Windows Server 2012 (64-bit)
• Mac OS X hosts:2
– 10.6 (Snow Leopard, 32-bit and 64-bit)
– 10.7 (Lion, 32-bit and 64-bit)
– 10.8 (Mountain Lion, 64-bit)
– 10.9 (Mavericks, 64-bit)
Intel hardware is required; please see chapter 14, Known limitations, page 229 also.
1 Support

for 64-bit Windows was added with VirtualBox 1.5.
Mac OS X support (beta stage) was added with VirtualBox 1.4, full support with 1.6. Mac OS X 10.4
(Tiger) support was removed with VirtualBox 3.1.

2 Preliminary

1 First steps
• Linux hosts (32-bit and 64-bit3 ). Among others, this includes:
– 10.04 (“Lucid Lynx”), 10.10 (“Maverick Meerkat), 11.04 (“Natty Narwhal”), 11.10
(“Oneiric Oncelot”), 12.04 (“Precise Pangolin”), 12.10 (“Quantal Quetzal”), 13.04
(“Raring Ringtail”), 13.10 (“Saucy Salamander”)
– Debian GNU/Linux 6.0 (“squeeze”) and 7.0 (“wheezy”)
– Oracle Enterprise Linux 5, Oracle Linux 6
– Redhat Enterprise Linux 5 and 6
– Fedora Core 6 to 19
– Gentoo Linux
– openSUSE 11.0, 11.1, 11.2, 11.3, 11.4, 12.1, 12.2
– Mandriva 2010 and 2011
It should be possible to use VirtualBox on most systems based on Linux kernel 2.6 or
3.x using either the VirtualBox installer or by doing a manual installation; see chapter
2.3, Installing on Linux hosts, page 37. However, the formally tested and supported Linux
distributions are those for which we offer a dedicated package.
Note that starting with VirtualBox 2.1, Linux 2.4-based host operating systems are no
longer supported.
• Solaris hosts (64-bit only) are supported with the restrictions listed in chapter 14, Known
limitations, page 229:
– Solaris 11 including Solaris 11 Express
– Solaris 10 (u8 and higher)
Note that the above list is informal. Oracle support for customers who have a support contract
is limited to a subset of the listed host operating systems. Also, any feature which is marked as
experimental is not supported. Feedback and suggestions about such features are welcome.

1.5 Installing VirtualBox and extension packs
VirtualBox comes in many different packages, and installation depends on your host operating
system. If you have installed software before, installation should be straightforward: on each
host platform, VirtualBox uses the installation method that is most common and easy to use. If
you run into trouble or have special requirements, please refer to chapter 2, Installation details,
page 35 for details about the various installation methods.
Starting with version 4.0, VirtualBox is split into several components.
1. The base package consists of all open-source components and is licensed under the GNU
General Public License V2.
2. Additional extension packs can be downloaded which extend the functionality of the
VirtualBox base package. Currently, Oracle provides the one extension pack, which can
be found at http://www.virtualbox.org and provides the following added functionality:
a) The virtual USB 2.0 (EHCI) device; see chapter 3.10.1, USB settings, page 56.
b) VirtualBox Remote Desktop Protocol (VRDP) support; see chapter 7.1, Remote display
(VRDP support), page 103.
3 Support

for 64-bit Linux was added with VirtualBox 1.4.

1 First steps
c) Host webcam passthrough; see chapter chapter 9.7.1, Using a host webcam in the
guest, page 168.
d) Intel PXE boot ROM.
e) Experimental support for PCI passthrough on Linux hosts; see chapter 9.6, PCI
passthrough, page 167.
VirtualBox extension packages have a .vbox-extpack file name extension. To install an
extension, simply double-click on the package file and a Network Operations Manager
window will appear, guiding you through the required steps.
To view the extension packs that are currently installed, please start the VirtualBox Manager (see the next section). From the “File” menu, please select “Preferences”. In the
window that shows up, go to the “Extensions” category which shows you the extensions
which are currently installed and allows you to remove a package or add a new one.
Alternatively you can use VBoxManage on the command line: see chapter 8.36, VBoxManage extpack, page 157 for details.

1.6 Starting VirtualBox
After installation, you can start VirtualBox as follows:
• On a Windows host, in the standard “Programs” menu, click on the item in the “VirtualBox”
group. On Vista or Windows 7, you can also type “VirtualBox” in the search box of the
“Start” menu.
• On a Mac OS X host, in the Finder, double-click on the “VirtualBox” item in the “Applications” folder. (You may want to drag this item onto your Dock.)
• On a Linux or Solaris host, depending on your desktop environment, a “VirtualBox” item
may have been placed in either the “System” or “System Tools” group of your “Applications”
menu. Alternatively, you can type VirtualBox in a terminal.
When you start VirtualBox for the first time, a window like the following should come up:

1 First steps
This window is called the “VirtualBox Manager”. On the left, you can see a pane that will later
list all your virtual machines. Since you have not created any, the list is empty. A row of buttons
above it allows you to create new VMs and work on existing VMs, once you have some. The pane
on the right displays the properties of the virtual machine currently selected, if any. Again, since
you don’t have any machines yet, the pane displays a welcome message.
To give you an idea what VirtualBox might look like later, after you have created many machines, here’s another example:

1.7 Creating your first virtual machine
Click on the “New” button at the top of the VirtualBox Manager window. A wizard will pop up
to guide you through setting up a new virtual machine (VM):

On the following pages, the wizard will ask you for the bare minimum of information that is
needed to create a VM, in particular:
1. The VM name will later be shown in the VM list of the VirtualBox Manager window, and
it will be used for the VM’s files on disk. Even though any name could be used, keep in

1 First steps
mind that once you have created a few VMs, you will appreciate if you have given your
VMs rather informative names; “My VM” would thus be less useful than “Windows XP SP2
with OpenOffice”.
2. For “Operating System Type”, select the operating system that you want to install later.
The supported operating systems are grouped; if you want to install something very unusual that is not listed, select “Other”. Depending on your selection, VirtualBox will enable
or disable certain VM settings that your guest operating system may require. This is particularly important for 64-bit guests (see chapter 3.1.2, 64-bit guests, page 46). It is therefore
recommended to always set it to the correct value.
3. On the next page, select the memory (RAM) that VirtualBox should allocate every time
the virtual machine is started. The amount of memory given here will be taken away from
your host machine and presented to the guest operating system, which will report this size
as the (virtual) computer’s installed RAM.
Note: Choose this setting carefully! The memory you give to the VM will not be
available to your host OS while the VM is running, so do not specify more than you can
spare. For example, if your host machine has 1 GB of RAM and you enter 512 MB as
the amount of RAM for a particular virtual machine, while that VM is running, you will
only have 512 MB left for all the other software on your host. If you run two VMs at
the same time, even more memory will be allocated for the second VM (which may not
even be able to start if that memory is not available). On the other hand, you should
specify as much as your guest OS (and your applications) will require to run properly.
A Windows XP guest will require at least a few hundred MB RAM to run properly, and
Windows Vista will even refuse to install with less than 512 MB. Of course, if you want to
run graphics-intensive applications in your VM, you may require even more RAM.
So, as a rule of thumb, if you have 1 GB of RAM or more in your host computer, it is usually
safe to allocate 512 MB to each VM. But, in any case, make sure you always have at least
256 to 512 MB of RAM left on your host operating system. Otherwise you may cause your
host OS to excessively swap out memory to your hard disk, effectively bringing your host
system to a standstill.
As with the other settings, you can change this setting later, after you have created the VM.
4. Next, you must specify a virtual hard disk for your VM.
There are many and potentially complicated ways in which VirtualBox can provide hard
disk space to a VM (see chapter 5, Virtual storage, page 80 for details), but the most
common way is to use a large image file on your “real” hard disk, whose contents VirtualBox
presents to your VM as if it were a complete hard disk. This file represents an entire hard
disk then, so you can even copy it to another host and use it with another VirtualBox
installation.
The wizard shows you the following window:

1 First steps

Here you have the following options:
• To create a new, empty virtual hard disk, press the “New” button.
• You can pick an existing disk image file.
The drop-down list presented in the window contains all disk images which are currently remembered by VirtualBox, probably because they are currently attached to a
virtual machine (or have been in the past).
Alternatively, you can click on the small folder button next to the drop-down list to
bring up a standard file dialog, which allows you to pick any disk image file on your
host disk.
Most probably, if you are using VirtualBox for the first time, you will want to create a new
disk image. Hence, press the “New” button.
This brings up another window, the “Create New Virtual Disk Wizard”, which helps you
create a new disk image file in the new virtual machine’s folder.
VirtualBox supports two types of image files:
• A dynamically allocated file will only grow in size when the guest actually stores
data on its virtual hard disk. It will therefore initially be small on the host hard drive
and only later grow to the size specified as it is filled with data.
• A fixed-size file will immediately occupy the file specified, even if only a fraction of
the virtual hard disk space is actually in use. While occupying much more space, a
fixed-size file incurs less overhead and is therefore slightly faster than a dynamically
allocated file.
For details about the differences, please refer to chapter 5.2, Disk image files (VDI, VMDK,
VHD, HDD), page 82.
To prevent your physical hard disk from running full, VirtualBox limits the size of the image
file. Still, it needs to be large enough to hold the contents of your operating system and the
applications you want to install – for a modern Windows or Linux guest, you will probably
need several gigabytes for any serious use:

1 First steps

After having selected or created your image file, again press “Next” to go to the next page.
5. After clicking on “Finish”, your new virtual machine will be created. You will then see it
in the list on the left side of the Manager window, with the name you entered initially.

Note: After becoming familiar with the use of wizards, consider using the Expert Mode
available in some wizards. Where available, this is selectable using a button, and
speeds up user processes using wizards.

1.8 Running your virtual machine
To start a virtual machine, you have several options:
• Double-click on its entry in the list within the Manager window or
• select its entry in the list in the Manager window it and press the “Start” button at the top
or
• for virtual machines created with VirtualBox 4.0 or later, navigate to the “VirtualBox VMs”
folder in your system user’s home directory, find the subdirectory of the machine you want
to start and double-click on the machine settings file (with a .vbox file extension).
This opens up a new window, and the virtual machine which you selected will boot up. Everything which would normally be seen on the virtual system’s monitor is shown in the window, as
can be seen with the image in chapter 1.2, Some terminology, page 12.
In general, you can use the virtual machine much like you would use a real computer. There
are couple of points worth mentioning however.

1.8.1 Starting a new VM for the first time
When a VM gets started for the first time, another wizard – the “First Start Wizard” – will
pop up to help you select an installation medium. Since the VM is created empty, it would
otherwise behave just like a real computer with no operating system installed: it will do nothing
and display an error message that no bootable operating system was found.
For this reason, the wizard helps you select a medium to install an operating system from.

1 First steps
• If you have physical CD or DVD media from which you want to install your guest operating
system (e.g. in the case of a Windows installation CD or DVD), put the media into your
host’s CD or DVD drive.
Then, in the wizard’s drop-down list of installation media, select “Host drive” with the
correct drive letter (or, in the case of a Linux host, device file). This will allow your VM to
access the media in your host drive, and you can proceed to install from there.
• If you have downloaded installation media from the Internet in the form of an ISO image
file (most probably in the case of a Linux distribution), you would normally burn this file
to an empty CD or DVD and proceed as just described. With VirtualBox however, you can
skip this step and mount the ISO file directly. VirtualBox will then present this file as a CD
or DVD-ROM drive to the virtual machine, much like it does with virtual hard disk images.
For this case, the wizard’s drop-down list contains a list of installation media that were
previously used with VirtualBox.
If your medium is not in the list (especially if you are using VirtualBox for the first time),
select the small folder icon next to the drop-down list to bring up a standard file dialog,
with which you can pick the image file on your host disks.
In both cases, after making the choices in the wizard, you will be able to install your operating
system.

1.8.2 Capturing and releasing keyboard and mouse
As of version 3.2, VirtualBox provides a virtual USB tablet device to new virtual machines through
which mouse events are communicated to the guest operating system. As a result, if you are
running a modern guest operating system that can handle such devices, mouse support may
work out of the box without the mouse being “captured” as described below; see chapter 3.4.1,
“Motherboard” tab, page 49 for more information.
Otherwise, if the virtual machine only sees standard PS/2 mouse and keyboard devices, since
the operating system in the virtual machine does not “know” that it is not running on a real
computer, it expects to have exclusive control over your keyboard and mouse. This is, however,
not the case since, unless you are running the VM in full screen mode, your VM needs to share
keyboard and mouse with other applications and possibly other VMs on your host.
As a result, initially after installing a guest operating system and before you install the Guest
Additions (we will explain this in a minute), only one of the two – your VM or the rest of your
computer – can “own” the keyboard and the mouse. You will see a second mouse pointer which
will always be confined to the limits of the VM window. Basically, you activate the VM by clicking
inside it.
To return ownership of keyboard and mouse to your host operating system, VirtualBox reserves
a special key on your keyboard for itself: the “host key”. By default, this is the right Control
key on your keyboard; on a Mac host, the default host key is the left Command key. You can
change this default in the VirtualBox Global Settings, see chapter 1.15, Global Settings, page 33.
In any case, the current setting for the host key is always displayed at the bottom right of your
VM window, should you have forgotten about it:

1 First steps

In detail, all this translates into the following:
• Your keyboard is owned by the VM if the VM window on your host desktop has the keyboard focus (and then, if you have many windows open in your guest operating system
as well, the window that has the focus in your VM). This means that if you want to type
within your VM, click on the title bar of your VM window first.
To release keyboard ownership, press the Host key (as explained above, typically the right
Control key).
Note that while the VM owns the keyboard, some key sequences (like Alt-Tab for example)
will no longer be seen by the host, but will go to the guest instead. After you press the
host key to re-enable the host keyboard, all key presses will go through the host again, so
that sequences like Alt-Tab will no longer reach the guest. For technical reasons it may
not be possible for the VM to get all keyboard input even when it does own the keyboard.
Examples of this are the Ctrl-Alt-Del sequence on Windows hosts or single keys grabbed by
other applications on X11 hosts like the GNOME desktop’s “Control key highlights mouse
pointer” functionality.
• Your mouse is owned by the VM only after you have clicked in the VM window. The host
mouse pointer will disappear, and your mouse will drive the guest’s pointer instead of your
normal mouse pointer.
Note that mouse ownership is independent of that of the keyboard: even after you have
clicked on a titlebar to be able to type into the VM window, your mouse is not necessarily
owned by the VM yet.
To release ownership of your mouse by the VM, also press the Host key.
As this behavior can be inconvenient, VirtualBox provides a set of tools and device drivers
for guest systems called the “VirtualBox Guest Additions” which make VM keyboard and mouse
operation a lot more seamless. Most importantly, the Additions will get rid of the second “guest”
mouse pointer and make your host mouse pointer work directly in the guest.
This will be described later in chapter 4, Guest Additions, page 60.

1.8.3 Typing special characters
Operating systems expect certain key combinations to initiate certain procedures. Some of these
key combinations may be difficult to enter into a virtual machine, as there are three candidates
as to who receives keyboard input: the host operating system, VirtualBox, or the guest operating
system. Who of these three receives keypresses depends on a number of factors, including the
key itself.
• Host operating systems reserve certain key combinations for themselves. For example, it
is impossible to enter the Ctrl+Alt+Delete combination if you want to reboot the guest

1 First steps
operating system in your virtual machine, because this key combination is usually hardwired into the host OS (both Windows and Linux intercept this), and pressing this key
combination will therefore reboot your host.
Also, on Linux and Solaris hosts, which use the X Window System, the key combination
Ctrl+Alt+Backspace normally resets the X server (to restart the entire graphical user
interface in case it got stuck). As the X server intercepts this combination, pressing it will
usually restart your host graphical user interface (and kill all running programs, including
VirtualBox, in the process).
Third, on Linux hosts supporting virtual terminals, the key combination Ctrl+Alt+Fx
(where Fx is one of the function keys from F1 to F12) normally allows to switch between
virtual terminals. As with Ctrl+Alt+Delete, these combinations are intercepted by the host
operating system and therefore always switch terminals on the host.
If, instead, you want to send these key combinations to the guest operating system in the
virtual machine, you will need to use one of the following methods:
– Use the items in the “Machine” menu of the virtual machine window. There you will
find “Insert Ctrl+Alt+Delete” and “Ctrl+Alt+Backspace”; the latter will only have an
effect with Linux or Solaris guests, however.
– Press special key combinations with the Host key (normally the right Control key),
which VirtualBox will then translate for the virtual machine:
∗ Host key + Del to send Ctrl+Alt+Del (to reboot the guest);
∗ Host key + Backspace to send Ctrl+Alt+Backspace (to restart the graphical user
interface of a Linux or Solaris guest);
∗ Host key + F1 (or other function keys) to simulate Ctrl+Alt+F1 (or other function keys, i.e. to switch between virtual terminals in a Linux guest).
• For some other keyboard combinations such as Alt-Tab (to switch between open windows),
VirtualBox allows you to configure whether these combinations will affect the host or the
guest, if a virtual machine currently has the focus. This is a global setting for all virtual
machines and can be found under “File” -> “Preferences” -> “Input” -> “Auto-capture
keyboard”.

1.8.4 Changing removable media
While a virtual machine is running, you can change removable media in the “Devices” menu of
the VM’s window. Here you can select in detail what VirtualBox presents to your VM as a CD,
DVD, or floppy.
The settings are the same as would be available for the VM in the “Settings” dialog of the
VirtualBox main window, but since that dialog is disabled while the VM is in the “running” or
“saved” state, this extra menu saves you from having to shut down and restart the VM every time
you want to change media.
Hence, in the “Devices” menu, VirtualBox allows you to attach the host drive to the guest or
select a floppy or DVD image using the Disk Image Manager, all as described in chapter 1.11,
Virtual machine configuration, page 30.

1.8.5 Resizing the machine’s window
You can resize the virtual machine’s window when it is running. In that case, one of three things
will happen:
1. If you have “scale mode” enabled, then the virtual machine’s screen will be scaled to the
size of the window. This can be useful if you have many machines running and want to

1 First steps
have a look at one of them while it is running in the background. Alternatively, it might
be useful to enlarge a window if the VM’s output screen is very small, for example because
you are running an old operating system in it.
To enable scale mode, press the host key + C, or select “Scale mode” from the “Machine”
menu in the VM window. To leave scale mode, press the host key + C again.
The aspect ratio of the guest screen is preserved when resizing the window. To ignore the
aspect ratio, press Shift during the resize operation.
Please see chapter 14, Known limitations, page 229 for additional remarks.
2. If you have the Guest Additions installed and they support automatic resizing, the Guest
Additions will automatically adjust the screen resolution of the guest operating system. For
example, if you are running a Windows guest with a resolution of 1024x768 pixels and you
then resize the VM window to make it 100 pixels wider, the Guest Additions will change
the Windows display resolution to 1124x768.
Please see chapter 4, Guest Additions, page 60 for more information about the Guest Additions.
3. Otherwise, if the window is bigger than the VM’s screen, the screen will be centered. If it
is smaller, then scroll bars will be added to the machine window.

1.8.6 Saving the state of the machine
When you click on the “Close” button of your virtual machine window (at the top right of the window, just like you would close any other window on your system), VirtualBox asks you whether
you want to “save” or “power off” the VM. (As a shortcut, you can also press the Host key together
with “Q”.)

The difference between these three options is crucial. They mean:
• Save the machine state: With this option, VirtualBox “freezes” the virtual machine by
completely saving its state to your local disk.
When you start the VM again later, you will find that the VM continues exactly where it
was left off. All your programs will still be open, and your computer resumes operation.
Saving the state of a virtual machine is thus in some ways similar to suspending a laptop
computer (e.g. by closing its lid).
• Send the shutdown signal. This will send an ACPI shutdown signal to the virtual machine,
which has the same effect as if you had pressed the power button on a real computer. So
long as the VM is running a fairly modern operating system, this should trigger a proper
shutdown mechanism from within the VM.
• Power off the machine: With this option, VirtualBox also stops running the virtual machine, but without saving its state.

1 First steps
Warning: This is equivalent to pulling the power plug on a real computer without
shutting it down properly. If you start the machine again after powering it off, your
operating system will have to reboot completely and may begin a lengthy check of
its (virtual) system disks. As a result, this should not normally be done, since it can
potentially cause data loss or an inconsistent state of the guest system on disk.
As an exception, if your virtual machine has any snapshots (see the next chapter), you can
use this option to quickly restore the current snapshot of the virtual machine. In that
case, powering off the machine will not disrupt its state, but any changes made since that
snapshot was taken will be lost.
The “Discard” button in the VirtualBox Manager window discards a virtual machine’s saved
state. This has the same effect as powering it off, and the same warnings apply.

1.9 Using VM groups
VM groups enable the user to create ad hoc groups of VMs, and to manage and perform functions
on them collectively, as well as individually. There are a number of features relating to groups:
1. Create a group using GUI option 1) Drag one VM on top of another VM.
Create a group using GUI option 2) Select multiple VMs and select “Group” on the right
click menu, as follows:

2. Command line option 1) Create group and assign VM:
VBoxManage modifyvm "Fred" --groups "/TestGroup"

Command line option 2) Detach VM from group, and delete group if empty:
VBoxManage modifyvm "Fred" --groups ""

3. Multiple groups e.g.:
VBoxManage modifyvm "Fred" --groups "/TestGroup,/TestGroup2"

1 First steps
4. Nested groups – hierarchy of groups e.g.:
VBoxManage modifyvm "Fred" --groups "/TestGroup/TestGroup2"

5. Summary of group commands: Start, Pause, Reset, Close (save state, send shutdown signal,
poweroff), Discard Saved State, Show in File System, Sort.

1.10 Snapshots
With snapshots, you can save a particular state of a virtual machine for later use. At any later
time, you can revert to that state, even though you may have changed the VM considerably since
then. A snapshot of a virtual machine is thus similar to a machine in “saved” state, as described
above, but there can be many of them, and these saved states are preserved.
You can see the snapshots of a virtual machine by first selecting a machine in the VirtualBox
Manager and then clicking on the “Snapshots” button at the top right. Until you take a snapshot
of the machine, the list of snapshots will be empty except for the “Current state” item, which
represents the “Now” point in the lifetime of the virtual machine.

1.10.1 Taking, restoring and deleting snapshots
There are three operations related to snapshots:
1. You can take a snapshot. This makes a copy of the machine’s current state, to which you
can go back at any given time later.
• If your VM is currently running, select “Take snapshot” from the “Machine” pull-down
menu of the VM window.
• If your VM is currently in either the “saved” or the “powered off” state (as displayed
next to the VM in the VirtualBox main window), click on the “Snapshots” tab on the
top right of the main window, and then
– either on the small camera icon (for “Take snapshot”) or
– right-click on the “Current State” item in the list and select “Take snapshot” from
the menu.
In any case, a window will pop up and ask you for a snapshot name. This name is purely
for reference purposes to help you remember the state of the snapshot. For example, a
useful name would be “Fresh installation from scratch, no Guest Additions”, or “Service
Pack 3 just installed”. You can also add a longer text in the “Description” field if you want.
Your new snapshot will then appear in the snapshots list. Underneath your new snapshot,
you will see an item called “Current state”, signifying that the current state of your VM is
a variation based on the snapshot you took earlier. If you later take another snapshot, you
will see that they will be displayed in sequence, and each subsequent snapshot is derived
from an earlier one:

1 First steps

VirtualBox imposes no limits on the number of snapshots you can take. The only practical
limitation is disk space on your host: each snapshot stores the state of the virtual machine
and thus occupies some disk space. (See the next section for details on what exactly is
stored in a snapshot.)
2. You can restore a snapshot by right-clicking on any snapshot you have taken in the list
of snapshots. By restoring a snapshot, you go back (or forward) in time: the current state
of the machine is lost, and the machine is restored to the exact state it was in when the
snapshot was taken.4
Note: Restoring a snapshot will affect the virtual hard drives that are connected to your
VM, as the entire state of the virtual hard drive will be reverted as well. This means also
that all files that have been created since the snapshot and all other file changes will be
lost. In order to prevent such data loss while still making use of the snapshot feature, it
is possible to add a second hard drive in “write-through” mode using the VBoxManage
interface and use it to store your data. As write-through hard drives are not included in
snapshots, they remain unaltered when a machine is reverted. See chapter 5.4, Special
image write modes, page 85 for details.
To avoid losing the current state when restoring a snapshot, you can create a new snapshot
before the restore.
By restoring an earlier snapshot and taking more snapshots from there, it is even possible
to create a kind of alternate reality and to switch between these different histories of the
virtual machine. This can result in a whole tree of virtual machine snapshots, as shown in
the screenshot above.
3. You can also delete a snapshot, which will not affect the state of the virtual machine, but
only release the files on disk that VirtualBox used to store the snapshot data, thus freeing
4 Both the terminology and the functionality of restoring snapshots has changed with VirtualBox 3.1.

Before that version,
it was only possible to go back to the very last snapshot taken – not earlier ones, and the operation was called “Discard
current state” instead of “Restore last snapshot”. The limitation has been lifted with version 3.1. It is now possible to
restore any snapshot, going backward and forward in time.

1 First steps
disk space. To delete a snapshot, right-click on it in the snapshots tree and select “Delete”.
As of VirtualBox 3.2, snapshots can be deleted even while a machine is running.
Note: Whereas taking and restoring snapshots are fairly quick operations, deleting a
snapshot can take a considerable amount of time since large amounts of data may need
to be copied between several disk image files. Temporary disk files may also need large
amounts of disk space while the operation is in progress.
There are some situations which cannot be handled while a VM is running, and you will
get an appropriate message that you need to perform this snapshot deletion when the VM
is shut down.

1.10.2 Snapshot contents
Think of a snapshot as a point in time that you have preserved. More formally, a snapshot consists
of three things:
• It contains a complete copy of the VM settings, including the hardware configuration, so
that when you restore a snapshot, the VM settings are restored as well. (For example, if
you changed the hard disk configuration or the VM’s system settings, that change is undone
when you restore the snapshot.)
The copy of the settings is stored in the machine configuration, an XML text file, and thus
occupies very little space.
• The complete state of all the virtual disks attached to the machine is preserved. Going back
to a snapshot means that all changes that had been made to the machine’s disks – file by
file, bit by bit – will be undone as well. Files that were since created will disappear, files
that were deleted will be restored, changes to files will be reverted.
(Strictly speaking, this is only true for virtual hard disks in “normal” mode. As mentioned
above, you can configure disks to behave differently with snapshots; see chapter 5.4, Special
image write modes, page 85. Even more formally and technically correct, it is not the virtual
disk itself that is restored when a snapshot is restored. Instead, when a snapshot is taken,
VirtualBox creates differencing images which contain only the changes since the snapshot
were taken, and when the snapshot is restored, VirtualBox throws away that differencing
image, thus going back to the previous state. This is both faster and uses less disk space.
For the details, which can be complex, please see chapter 5.5, Differencing images, page
86.)
Creating the differencing image as such does not occupy much space on the host disk
initially, since the differencing image will initially be empty (and grow dynamically later
with each write operation to the disk). The longer you use the machine after having created
the snapshot, however, the more the differencing image will grow in size.
• Finally, if you took a snapshot while the machine was running, the memory state of the
machine is also saved in the snapshot (the same way the memory can be saved when you
close the VM window). When you restore such a snapshot, execution resumes at exactly
the point when the snapshot was taken.
The memory state file can be as large as the memory size of the virtual machine and will
therefore occupy quite some disk space as well.

1 First steps

1.11 Virtual machine configuration
When you select a virtual machine from the list in the Manager window, you will see a summary
of that machine’s settings on the right.
Clicking on the “Settings” button in the toolbar at the top brings up a detailed window where
you can configure many of the properties of the selected VM. But be careful: even though it
is possible to change all VM settings after installing a guest operating system, certain changes
might prevent a guest operating system from functioning correctly if done after installation.
Note: The “Settings” button is disabled while a VM is either in the “running” or “saved”
state. This is simply because the settings dialog allows you to change fundamental
characteristics of the virtual computer that is created for your guest operating system,
and this operating system may not take it well when, for example, half of its memory
is taken away from under its feet. As a result, if the “Settings” button is disabled, shut
down the current VM first.
VirtualBox provides a plethora of parameters that can be changed for a virtual machine. The
various settings that can be changed in the “Settings” window are described in detail in chapter
3, Configuring virtual machines, page 45. Even more parameters are available with the VirtualBox
command line interface; see chapter 8, VBoxManage, page 113.

1.12 Removing virtual machines
To remove a virtual machine which you no longer need, right-click on it in the Manager’s VM list
select “Remove” from the context menu that comes up.
A confirmation window will come up that allows you to select whether the machine should
only be removed from the list of machines or whether the files associated with it should also be
deleted.
The “Remove” menu item is disabled while a machine is running.

1.13 Cloning virtual machines
To experiment with a VM configuration, test different guest OS levels or to simply backup a VM,
VirtualBox can create a full or a linked copy of an existing VM.5
A wizard will guide you through the clone process:

5 Cloning

support was introduced with VirtualBox 4.1.

1 First steps

This wizard can be invoked from the context menu of the Manager’s VM list (select “Clone”) or
the “Snapshots” view of the selected VM. First choose a new name for the clone. When you select
Reinitialize the MAC address of all network cards every network card get a new MAC address
assigned. This is useful when both, the source VM and the cloned VM, have to operate on the
same network. If you leave this unchanged, all network cards have the same MAC address like
the one in the source VM. Depending on how you invoke the wizard you have different choices
for the cloning operation. First you need to decide if the clone should be linked to the source VM
or a fully independent clone should be created:
• Full clone: In this mode all depending disk images are copied to the new VM folder. The
clone can fully operate without the source VM.
• Linked clone: In this mode new differencing disk images are created where the parent
disk images are the source disk images. If you selected the current state of the source VM
as clone point, a new snapshot will be created implicitly.
After selecting the clone mode, you need to decide about what exactly should be cloned. You
can always create a clone of the current state only or all. When you select all, the current state
and in addition all snapshots are cloned. Have you started from a snapshot which has additional
children, you can also clone the current state and all children. This creates a clone starting with
this snapshot and includes all child snaphots.
The clone operation itself can be a lengthy operation depending on the size and count of
the attached disk images. Also keep in mind that every snapshot has differencing disk images
attached, which need to be cloned as well.
The “Clone” menu item is disabled while a machine is running.
For how to clone a VM at the command line, please see chapter 8.9, VBoxManage clonevm,
page 132.

1.14 Importing and exporting virtual machines
VirtualBox can import and export virtual machines in the industry-standard Open Virtualization
Format (OVF).6
OVF is a cross-platform standard supported by many virtualization products which allows
for creating ready-made virtual machines that can then be imported into a virtualizer such as
6 OVF

support was originally introduced with VirtualBox 2.2 and has seen major improvements with every version since.

1 First steps
VirtualBox. VirtualBox makes OVF import and export easy to access and supports it from the
Manager window as well as its command-line interface. This allows for packaging so-called
virtual appliances: disk images together with configuration settings that can be distributed
easily. This way one can offer complete ready-to-use software packages (operating systems with
applications) that need no configuration or installation except for importing into VirtualBox.
Note: The OVF standard is complex, and support in VirtualBox is an ongoing process.
In particular, no guarantee is made that VirtualBox supports all appliances created by
other virtualization software. For a list of known limitations, please see chapter 14,
Known limitations, page 229.
Appliances in OVF format can appear in two variants:
1. They can come in several files, as one or several disk images, typically in the widely-used
VMDK format (see chapter 5.2, Disk image files (VDI, VMDK, VHD, HDD), page 82) and a
textual description file in an XML dialect with an .ovf extension. These files must then
reside in the same directory for VirtualBox to be able to import them.
2. Alternatively, the above files can be packed together into a single archive file, typically
with an .ova extension. (Such archive files use a variant of the TAR archive format and
can therefore be unpacked outside of VirtualBox with any utility that can unpack standard
TAR files.)
To import an appliance in one of the above formats, simply double-click on the OVF/OVA file.7
Alternatively, select “File” -> “Import appliance” from the Manager window. In the file dialog
that comes up, navigate to the file with either the .ovf or the .ova file extension.
If VirtualBox can handle the file, a dialog similar to the following will appear:

7 Starting

with version 4.0, VirtualBox creates file type associations for OVF and OVA files on your host operating system.

1 First steps
This presents the virtual machines described in the OVF file and allows you to change the virtual machine settings by double-clicking on the description items. Once you click on “Import”,
VirtualBox will copy the disk images and create local virtual machines with the settings described
in the dialog. These will then show up in the Manager’s list of virtual machines.
Note that since disk images tend to be big, and VMDK images that come with virtual appliances
are typically shipped in a special compressed format that is unsuitable for being used by virtual
machines directly, the images will need to be unpacked and copied first, which can take a few
minutes.
For how to import an image at the command line, please see chapter 8.10, VBoxManage import,
page 132.
Conversely, to export virtual machines that you already have in VirtualBox, select “File” ->
“Export appliance”. A different dialog window shows up that allows you to combine several
virtual machines into an OVF appliance. Then, select the target location where the target files
should be stored, and the conversion process begins. This can again take a while.
For how to export an image at the command line, please see chapter 8.11, VBoxManage export,
page 133.
Note: OVF cannot describe snapshots that were taken for a virtual machine. As a
result, when you export a virtual machine that has snapshots, only the current state of
the machine will be exported, and the disk images in the export will have a “flattened”
state identical to the current state of the virtual machine.

1.15 Global Settings
The global settings dialog can be reached through the File menu, selecting the Preferences...
item. It offers a selection of settings which apply to all virtual machines of the current user or in
the case of Extensions to the entire system:
1. General Enables the user to specify the default folder/directory for VM files, and the VRDP
Authentication Library.
2. Input Enables the user to specify the Host Key. It identifies the key that toggles whether the
cursor is in the focus of the VM or the Host operating system windows (see chapter 1.8.2,
Capturing and releasing keyboard and mouse, page 22) and which is also used to trigger
certain VM actions (see chapter 1.8.3, Typing special characters, page 23)
3. Update Enables the user to specify various settings for Automatic Updates.
4. Language Enables the user to specify the GUI language.
5. Display Enables the user to specify the screen resolution, and its width and height.
6. Network Enables the user to configure the details of Host Only Networks.
7. Extensions Enables the user to list and manage the installed extension packages.
8. Proxy Enables the user to configure a HTTP Proxy Server.

1.16 Alternative front-ends
As briefly mentioned in chapter 1.3, Features overview, page 13, VirtualBox has a very flexible
internal design that allows for using multiple interfaces to control the same virtual machines. To
illustrate, you can, for example, start a virtual machine with the VirtualBox Manager window

1 First steps
and then stop it from the command line. With VirtualBox’s support for the Remote Desktop
Protocol (RDP), you can even run virtual machines remotely on a headless server and have all
the graphical output redirected over the network.
In detail, the following front-ends are shipped in the standard VirtualBox package:
1. VirtualBox is the VirtualBox Manager. This graphical user interface uses the Qt toolkit;
most of this User Manual is dedicated to describing it. While this is the easiest to use, some
of the more advanced VirtualBox features are kept away from it to keep it simple.
2. VBoxManage is our command-line interface for automated and very detailed control of
every aspect of VirtualBox. It is described in chapter 8, VBoxManage, page 113.
3. VBoxSDL is an alternative, simple graphical front-end with an intentionally limited feature set, designed to only display virtual machines that are controlled in detail with
VBoxManage. This is interesting for business environments where displaying all the bells
and whistles of the full GUI is not feasible. VBoxSDL is described in chapter 9.1, VBoxSDL,
the simplified VM displayer, page 158.
4. Finally, VBoxHeadless is yet another front-end that produces no visible output on the host
at all, but merely acts as a RDP server if the VirtualBox Remote Desktop Extension (VRDE)
is installed. As opposed to the other graphical interfaces, the headless front-end requires
no graphics support. This is useful, for example, if you want to host your virtual machines
on a headless Linux server that has no X Window system installed. For details, see chapter
7.1.2, VBoxHeadless, the remote desktop server, page 104.
If the above front-ends still do not satisfy your particular needs, it is possible to create yet another
front-end to the complex virtualization engine that is the core of VirtualBox, as the VirtualBox
core neatly exposes all of its features in a clean API; please refer to chapter 11, VirtualBox
programming interfaces, page 208.

2 Installation details
As installation of VirtualBox varies depending on your host operating system, we provide installation instructions in four separate chapters for Windows, Mac OS X, Linux and Solaris, respectively.

2.1 Installing on Windows hosts
2.1.1 Prerequisites
For the various versions of Windows that we support as host operating systems, please refer to
chapter 1.4, Supported host operating systems, page 15.
In addition, Windows Installer 1.1 or higher must be present on your system. This should be
the case if you have all recent Windows updates installed.

2.1.2 Performing the installation
The VirtualBox installation can be started
• either by double-clicking on its executable file (contains both 32- and 64-bit architectures)
• or by entering
VirtualBox.exe -extract

on the command line. This will extract both installers into a temporary directory in which
you’ll then find the usual .MSI files. Then you can do a
msiexec /i VirtualBox--MultiArch_.msi

to perform the installation.
In either case, this will display the installation welcome dialog and allow you to choose where
to install VirtualBox to and which components to install. In addition to the VirtualBox application, the following components are available:
USB support This package contains special drivers for your Windows host that VirtualBox requires to fully support USB devices inside your virtual machines.
Networking This package contains extra networking drivers for your Windows host that
VirtualBox needs to support Bridged Networking (to make your VM’s virtual network cards
accessible from other machines on your physical network).
Python Support This package contains Python scripting support for the VirtualBox API (see
chapter 11, VirtualBox programming interfaces, page 208). For this to work, an already
working Windows Python installation on the system is required.1
Depending on your Windows configuration, you may see warnings about “unsigned drivers” or
similar. Please select “Continue” on these warnings as otherwise VirtualBox might not function
correctly after installation.
1 See,

for example, http://www.python.org/download/windows/.

2 Installation details
The installer will create a “VirtualBox” group in the Windows “Start” menu which allows you
to launch the application and access its documentation.
With standard settings, VirtualBox will be installed for all users on the local system. In case
this is not wanted, you have to invoke the installer by first extracting it by using
VirtualBox.exe -extract

and then do as follows:
VirtualBox.exe -msiparams ALLUSERS=2

or
msiexec /i VirtualBox--MultiArch_.msi ALLUSERS=2

on the extracted .MSI files. This will install VirtualBox only for the current user.
If you do not want to install all features of VirtualBox, you can set the optional ADDLOCAL
parameter to explicitly name the features to be installed. The following features are available:
VBoxApplication Main binaries of VirtualBox.
Note: This feature must not be absent since it contains the minimum set of files to have
working VirtualBox installation.

VBoxUSB USB support.
VBoxNetwork All networking support; includes the VBoxNetworkFlt and VBoxNetworkAdp features (see below).
VBoxNetworkFlt Bridged networking support.
VBoxNetworkAdp Host-only networking support.
VBoxPython Python support.
For example, to only install USB support along with the main binaries, do a:
VirtualBox.exe -msiparams ADDLOCAL=VBoxApplication,VBoxUSB

or
msiexec /i VirtualBox--MultiArch_.msi ADDLOCAL=VBoxApplication,VBoxUSB

2.1.3 Uninstallation
As VirtualBox uses the standard Microsoft Windows installer, VirtualBox can be safely uninstalled
at any time by choosing the program entry in the “Add/Remove Programs” applet in the Windows
Control Panel.

2.1.4 Unattended installation
Unattended installations can be performed using the standard MSI support.

2 Installation details

2.2 Installing on Mac OS X hosts
2.2.1 Performing the installation
For Mac OS X hosts, VirtualBox ships in a disk image (dmg) file. Perform the following steps:
1. Double-click on that file to have its contents mounted.
2. A window will open telling you to double click on the VirtualBox.mpkg installer file
displayed in that window.
3. This will start the installer, which will allow you to select where to install VirtualBox to.
After installation, you can find a VirtualBox icon in the “Applications” folder in the Finder.

2.2.2 Uninstallation
To uninstall VirtualBox, open the disk image (dmg) file again and double-click on the uninstall
icon contained therein.

2.2.3 Unattended installation
To perform a non-interactive installation of VirtualBox you can use the command line version of
the installer application.
Mount the disk image (dmg) file as described in the normal installation. Then open a terminal
session and execute:
sudo installer -pkg /Volumes/VirtualBox/VirtualBox.mpkg \
-target /Volumes/Macintosh\ HD

2.3 Installing on Linux hosts
2.3.1 Prerequisites
For the various versions of Linux that we support as host operating systems, please refer to
chapter 1.4, Supported host operating systems, page 15.
You will need to install the following packages on your Linux system before starting the installation (some systems will do this for you automatically when you install VirtualBox):
• Qt 4.6.2 or higher;
• SDL 1.2.7 or higher (this graphics library is typically called libsdl or similar).

Note: To be precise, these packages are only required if you want to run the VirtualBox
graphical user interfaces. In particular, VirtualBox, the graphical VirtualBox manager,
requires both Qt and SDL; VBoxSDL, our simplified GUI, requires only SDL. By contrast,
if you only want to run VBoxHeadless, neither Qt nor SDL are required.

2 Installation details

2.3.2 The VirtualBox kernel module
VirtualBox uses a special kernel module called vboxdrv to perform physical memory allocation
and to gain control of the processor for guest system execution. Without this kernel module,
you can still use the VirtualBox manager to configure virtual machines, but they will not start. In
addition, there are the network kernel modules vboxnetflt and vboxnetadp which are required
for the more advanced networking features of VirtualBox.
The VirtualBox kernel module is automatically installed on your system when you install
VirtualBox. To maintain it with future kernel updates, for those Linux distributions which provide
it – most current ones – we recommend installing Dynamic Kernel Module Support (DKMS)2 .
This framework helps with building and upgrading kernel modules.
If DKMS is not already installed, execute one of the following:
• On an Ubuntu system:
sudo apt-get install dkms

• On a Fedora system:
yum install dkms

• On a Mandriva or Mageia system:
urpmi dkms

If DKMS is available and installed, the VirtualBox kernel module should always work automatically, and it will be automatically rebuilt if your host kernel is updated.
Otherwise, there are only two situations in which you will need to worry about the kernel
module:
1. The original installation fails. This probably means that your Linux system is not prepared
for building external kernel modules.
Most Linux distributions can be set up simply by installing the right packages - normally,
these will be the GNU compiler (GCC), GNU Make (make) and packages containing header
files for your kernel - and making sure that all system updates are installed and that the
system is running the most up-to-date kernel included in the distribution. The version
numbers of the header file packages must be the same as that of the kernel you are using.
• With Debian and Ubuntu releases, you must install the right version of the
linux-headers and if it exists the linux-kbuild package. Current Ubuntu releases
should have the right packages installed by default.
• In even older Debian and Ubuntu releases, you must install the right version of the
kernel-headers package.
• On Fedora and Redhat systems, the package is kernel-devel.
• On SUSE and openSUSE Linux, you must install the right versions of the
kernel-source and kernel-syms packages.
• If you have built your own kernel, you will need to make sure that you also installed
all the required header and other files for building external modules to the right locations. The details of how to do this will depend on how you built your kernel, and if
you are unsure you should consult the documentation which you followed to do so.
2. The kernel of your Linux host was updated and DKMS is not installed. In that case, the
kernel module will need to be reinstalled by executing (as root):
/etc/init.d/vboxdrv setup

2 See http://en.wikipedia.org/wiki/Dynamic_Kernel_Module_Support

for an introduction.

2 Installation details

2.3.3 Performing the installation
VirtualBox is available in a number of package formats native to various common Linux distributions (see chapter 1.4, Supported host operating systems, page 15 for details). In addition, there
is an alternative generic installer (.run) which should work on most Linux distributions.
2.3.3.1 Installing VirtualBox from a Debian/Ubuntu package
First, download the appropriate package for your distribution. The following examples assume
that you are installing to a 32-bit Ubuntu Raring system. Use dpkg to install the Debian package:
sudo dpkg -i VirtualBox-3.2_4.3.18_Ubuntu_raring_i386.deb

You will be asked to accept the VirtualBox Personal Use and Evaluation License. Unless you
answer “yes” here, the installation will be aborted.
The installer will also search for a VirtualBox kernel module suitable for your kernel. The package includes pre-compiled modules for the most common kernel configurations. If no suitable
kernel module is found, the installation script tries to build a module itself. If the build process
is not successful you will be shown a warning and the package will be left unconfigured. Please
have a look at /var/log/vbox-install.log to find out why the compilation failed. You may
have to install the appropriate Linux kernel headers (see chapter 2.3.2, The VirtualBox kernel
module, page 38). After correcting any problems, do
sudo /etc/init.d/vboxdrv setup

This will start a second attempt to build the module.
If a suitable kernel module was found in the package or the module was successfully built, the
installation script will attempt to load that module. If this fails, please see chapter 12.7.1, Linux
kernel module refuses to load, page 221 for further information.
Once VirtualBox has been successfully installed and configured, you can start it by selecting
“VirtualBox” in your start menu or from the command line (see chapter 2.3.5, Starting VirtualBox
on Linux, page 42).
2.3.3.2 Using the alternative installer (VirtualBox.run)
The alternative installer performs the following steps:
• It unpacks the application files to the target directory,
/opt/VirtualBox/

which cannot be changed.
• It builds the VirtualBox kernel modules (vboxdrv, vboxnetflt and vboxnetadp) and installs them.
• It creates /etc/init.d/vboxdrv, an init script to start the VirtualBox kernel module.
• It creates a new system group called vboxusers.
• It creates symbolic links in /usr/bin to the a shell script (/opt/VirtualBox/VBox) which
does some sanity checks and dispatches to the actual executables, VirtualBox, VBoxSDL,
VBoxVRDP, VBoxHeadless and VBoxManage
• It creates /etc/udev/rules.d/60-vboxdrv.rules, a description file for udev, if that is
present, which makes the USB devices accessible to all users in the vboxusers group.
• It writes the installation directory to /etc/vbox/vbox.cfg.

2 Installation details
The installer must be executed as root with either install or uninstall as the first parameter.
sudo ./VirtualBox.run install

Or if you do not have the “sudo” command available, run the following as root instead:
./VirtualBox.run install

After that you need to put every user which should be able to access USB devices from
VirtualBox guests in the group vboxusers, either through the GUI user management tools or
by running the following command as root:
sudo usermod -a -G vboxusers username

Note: The usermod command of some older Linux distributions does not support the
-a option (which adds the user to the given group without affecting membership of
other groups). In this case, find out the current group memberships with the groups
command and add all these groups in a comma-separated list to the command line after
the -G option, e.g. like this: usermod -G group1,group2,vboxusers username.

2.3.3.3 Performing a manual installation
If, for any reason, you cannot use the shell script installer described previously, you can also
perform a manual installation. Invoke the installer like this:
./VirtualBox.run --keep --noexec

This will unpack all the files needed for installation in the directory install under the current
directory. The VirtualBox application files are contained in VirtualBox.tar.bz2 which you can
unpack to any directory on your system. For example:
sudo mkdir /opt/VirtualBox
sudo tar jxf ./install/VirtualBox.tar.bz2 -C /opt/VirtualBox

or as root:
mkdir /opt/VirtualBox
tar jxf ./install/VirtualBox.tar.bz2 -C /opt/VirtualBox

The sources for VirtualBox’s kernel module are provided in the src directory. To build the
module, change to the directory and issue
make

If everything builds correctly, issue the following command to install the module to the appropriate module directory:
sudo make install

In case you do not have sudo, switch the user account to root and perform
make install

2 Installation details
The VirtualBox kernel module needs a device node to operate. The above make command
will tell you how to create the device node, depending on your Linux system. The procedure
is slightly different for a classical Linux setup with a /dev directory, a system with the now
deprecated devfs and a modern Linux system with udev.
On certain Linux distributions, you might experience difficulties building the module. You will
have to analyze the error messages from the build system to diagnose the cause of the problems.
In general, make sure that the correct Linux kernel sources are used for the build process.
Note that the /dev/vboxdrv kernel module device node must be owned by root:root and must
be read/writable only for the user.
Next, you will have to install the system initialization script for the kernel module:
cp /opt/VirtualBox/vboxdrv.sh /etc/init.d/vboxdrv

(assuming you installed VirtualBox to the /opt/VirtualBox directory) and activate the initialization script using the right method for your distribution. You should create VirtualBox’s
configuration file:
mkdir /etc/vbox
echo INSTALL_DIR=/opt/VirtualBox > /etc/vbox/vbox.cfg

and, for convenience, create the following symbolic links:
ln
ln
ln
ln

-sf
-sf
-sf
-sf

/opt/VirtualBox/VBox.sh
/opt/VirtualBox/VBox.sh
/opt/VirtualBox/VBox.sh
/opt/VirtualBox/VBox.sh

/usr/bin/VirtualBox
/usr/bin/VBoxManage
/usr/bin/VBoxHeadless
/usr/bin/VBoxSDL

2.3.3.4 Updating and uninstalling VirtualBox
Before updating or uninstalling VirtualBox, you must terminate any virtual machines which are
currently running and exit the VirtualBox or VBoxSVC applications. To update VirtualBox, simply
run the installer of the updated version. To uninstall VirtualBox, invoke the installer like this:
sudo ./VirtualBox.run uninstall

or as root
./VirtualBox.run uninstall

. Starting with version 2.2.2, you can uninstall the .run package by invoking
/opt/VirtualBox/uninstall.sh

To manually uninstall VirtualBox, simply undo the steps in the manual installation in reverse
order.
2.3.3.5 Automatic installation of Debian packages
The Debian packages will request some user feedback when installed for the first time. The
debconf system is used to perform this task. To prevent any user interaction during installation,
default values can be defined. A file vboxconf can contain the following debconf settings:
virtualbox virtualbox/module-compilation-allowed boolean true
virtualbox virtualbox/delete-old-modules boolean true

The first line allows compilation of the vboxdrv kernel module if no module was found for the
current kernel. The second line allows the package to delete any old vboxdrv kernel modules
compiled by previous installations.
These default settings can be applied with
debconf-set-selections vboxconf

prior to the installation of the VirtualBox Debian package.
In addition there are some common configuration options that can be set prior to the installation, described in chapter 2.3.3.7, Automatic installation options, page 42.

2 Installation details
2.3.3.6 Automatic installation of .rpm packages
The .rpm format does not provide a configuration system comparable to the debconf system. See
chapter 2.3.3.7, Automatic installation options, page 42 for how to set some common installation
options provided by VirtualBox.
2.3.3.7 Automatic installation options
To configure the installation process of our .deb and .rpm packages, you can create a response
file named /etc/default/virtualbox. The automatic generation of the udev rule can be prevented by the following setting:
INSTALL_NO_UDEV=1

The creation of the group vboxusers can be prevented by
INSTALL_NO_GROUP=1

If the line
INSTALL_NO_VBOXDRV=1

is specified, the package installer will not try to build the vboxdrv kernel module if no module
fitting the current kernel was found.

2.3.4 The vboxusers group
The Linux installers create the system user group vboxusers during installation. Any system
user who is going to use USB devices from VirtualBox guests must be a member of that group. A
user can be made a member of the group vboxusers through the GUI user/group management
or at the command line with
sudo usermod -a -G vboxusers username

2.3.5 Starting VirtualBox on Linux
The easiest way to start a VirtualBox program is by running the program of your choice
(VirtualBox, VBoxManage, VBoxSDL or VBoxHeadless) from a terminal. These are symbolic
links to VBox.sh that start the required program for you.
The following detailed instructions should only be of interest if you wish to execute VirtualBox
without installing it first. You should start by compiling the vboxdrv kernel module (see above)
and inserting it into the Linux kernel. VirtualBox consists of a service daemon (VBoxSVC) and
several application programs. The daemon is automatically started if necessary. All VirtualBox
applications will communicate with the daemon through Unix local domain sockets. There
can be multiple daemon instances under different user accounts and applications can only
communicate with the daemon running under the user account as the application. The local
domain socket resides in a subdirectory of your system’s directory for temporary files called
.vbox--ipc. In case of communication problems or server startup problems, you
may try to remove this directory.
All VirtualBox applications (VirtualBox, VBoxSDL, VBoxManage and VBoxHeadless) require
the VirtualBox directory to be in the library path:
LD_LIBRARY_PATH=. ./VBoxManage showvminfo "Windows XP"

2 Installation details

2.4 Installing on Solaris hosts
For the specific versions of Solaris that we support as host operating systems, please refer to
chapter 1.4, Supported host operating systems, page 15.
If you have a previously installed instance of VirtualBox on your Solaris host, please uninstall it
first before installing a new instance. Refer to chapter 2.4.4, Uninstallation, page 44 for uninstall
instructions.

2.4.1 Performing the installation
VirtualBox is available as a standard Solaris package. Download the VirtualBox SunOS package
which includes the 64-bit versions of VirtualBox. The installation must be performed as root and
from the global zone as the VirtualBox installer loads kernel drivers which cannot be done from
non-global zones. To verify which zone you are currently in, execute the zonename command.
Execute the following commands:
gunzip -cd VirtualBox-4.3.18-SunOS.tar.gz | tar xvf -

Starting with VirtualBox 3.1 the VirtualBox kernel package is no longer a separate package
and has been integrated into the main package. Install the VirtualBox package using:
pkgadd -d VirtualBox-4.3.18-SunOS.pkg

Note: If you are using Solaris Zones, to install VirtualBox only into the current zone
and not into any other zone, use pkgadd -G. For more information refer to the pkgadd
manual; see also chapter 2.4.6, Configuring a zone for running VirtualBox, page 44.
The installer will then prompt you to enter the package you wish to install. Choose “1” or
“all” and proceed. Next the installer will ask you if you want to allow the postinstall script to
be executed. Choose “y” and proceed as it is essential to execute this script which installs the
VirtualBox kernel module. Following this confirmation the installer will install VirtualBox and
execute the postinstall setup script.
Once the postinstall script has been executed your installation is now complete. You may now
safely delete the uncompressed package and autoresponse files from your system. VirtualBox
would be installed in /opt/VirtualBox.

2.4.2 The vboxuser group
Starting with VirtualBox 4.1, the installer creates the system user group vboxuser during installation for Solaris hosts that support the USB features required by VirtualBox. Any system user
who is going to use USB devices from VirtualBox guests must be a member of this group. A
user can be made a member of this group through the GUI user/group management or at the
command line by executing as root:
usermod -G vboxuser username

Note that adding an active user to that group will require that user to log out and back in
again. This should be done manually after successful installation of the package.

2 Installation details

2.4.3 Starting VirtualBox on Solaris
The easiest way to start a VirtualBox program is by running the program of your choice
(VirtualBox, VBoxManage, VBoxSDL or VBoxHeadless) from a terminal. These are symbolic
links to VBox.sh that start the required program for you.
Alternatively, you can directly invoke the required programs from /opt/VirtualBox. Using
the links provided is easier as you do not have to type the full path.
You can configure some elements of the VirtualBox Qt GUI such as fonts and colours by
executing VBoxQtconfig from the terminal.

2.4.4 Uninstallation
Uninstallation of VirtualBox on Solaris requires root permissions. To perform the uninstallation,
start a root terminal session and execute:
pkgrm SUNWvbox

After confirmation, this will remove VirtualBox from your system.
If you are uninstalling VirtualBox version 3.0 or lower, you need to remove the VirtualBox
kernel interface package, execute:
pkgrm SUNWvboxkern

2.4.5 Unattended installation
To perform a non-interactive installation of VirtualBox we have provided a response file named
autoresponse that the installer will use for responses to inputs rather than ask them from you.
Extract the tar.gz package as described in the normal installation. Then open a root terminal
session and execute:
pkgadd -d VirtualBox-4.3.18-SunOS-x86 -n -a autoresponse SUNWvbox

To perform a non-interactive uninstallation, open a root terminal session and execute:
pkgrm -n -a /opt/VirtualBox/autoresponse SUNWvbox

2.4.6 Configuring a zone for running VirtualBox
Starting with VirtualBox 1.6 it is possible to run VirtualBox from within Solaris zones. For
an introduction of Solaris zones, please refer to http://www.sun.com/bigadmin/features/
articles/solaris_zones.jsp.
Assuming that VirtualBox has already been installed into your zone, you need to give the zone
access to VirtualBox’s device node. This is done by performing the following steps. Start a root
terminal and execute:
zonecfg -z vboxzone

Inside the zonecfg prompt add the device resource and match properties to the zone. Here’s
how it can be done:
zonecfg:vboxzone>add device
zonecfg:vboxzone:device>set match=/dev/vboxdrv
zonecfg:vboxzone:device>end
zonecfg:vboxzone>verify
zonecfg:vboxzone>exit

If you are running VirtualBox 2.2.0 or above on Solaris 11 or Nevada hosts, you should add
a device for /dev/vboxusbmon too, similar to what was shown above. This does not apply to
Solaris 10 hosts due to lack of USB support.
Replace “vboxzone” with the name of the zone in which you intend to run VirtualBox. Next
reboot the zone using zoneadm and you should be able to run VirtualBox from within the configured zone.

3 Configuring virtual machines
Whereas chapter 1, First steps, page 11 gave you a quick introduction to VirtualBox and how to
get your first virtual machine running, the following chapter describes in detail how to configure
virtual machines.
You have considerable latitude in deciding what virtual hardware will be provided to the guest.
The virtual hardware can be used for communicating with the host system or with other guests.
For instance, if you provide VirtualBox with the image of a CD-ROM in an ISO file, VirtualBox
can present this image to a guest system as if it were a physical CD-ROM. Similarly, you can give
a guest system access to the real network via its virtual network card, and, if you so choose, give
the host system, other guests, or computers on the Internet access to the guest system.

3.1 Supported guest operating systems
Since VirtualBox is designed to provide a generic virtualization environment for x86 systems,
it may run operating systems of any kind, even those not listed here. However, the focus is to
optimize VirtualBox for the following guest systems:
Windows NT 4.0 All versions, editions and service packs are fully supported; however, there
are some issues with older service packs. We recommend to install service pack 6a. Guest
Additions are available with a limited feature set.
Windows 2000 / XP / Server 2003 / Vista / Server 2008 / Windows 7 / Windows 8 / Server 2012
All versions, editions and service packs are fully supported (including 64-bit versions, under the preconditions listed below). Guest Additions are available.
DOS / Windows 3.x / 95 / 98 / ME Limited testing has been performed. Use beyond legacy installation mechanisms not recommended. No Guest Additions available.
Linux 2.4 Limited support.
Linux 2.6 All versions/editions are fully supported (32 bits and 64 bits). Guest Additions are
available.
We strongly recommend using a Linux kernel version 2.6.13 or higher for better performance.
Note: Certain Linux kernel releases have bugs that prevent them from executing in a
virtual environment; please see chapter 12.4.3, Buggy Linux 2.6 kernel versions, page
218 for details.

Linux 3.x All versions/editions are fully supported (32 bits and 64 bits). Guest Additions are
available.
Solaris 10 (u6 and higher), Solaris 11 (including Solaris 11 Express) Fully supported (32
bits and 64 bits). Guest Additions are available.
FreeBSD Requires hardware virtualization to be enabled. Limited support. Guest Additions are
not available yet.

3 Configuring virtual machines
OpenBSD Requires hardware virtualization to be enabled. Versions 3.7 and later are supported.
Guest Additions are not available yet.
OS/2 Warp 4.5 Requires hardware virtualization to be enabled. We officially support MCP2
only; other OS/2 versions may or may not work. Guest Additions are available with a
limited feature set.1
Mac OS X VirtualBox 3.2 added experimental support for Mac OS X guests, but this comes with
restrictions. Please see the following section as well as chapter 14, Known limitations, page
229.

3.1.1 Mac OS X guests
Starting with version 3.2, VirtualBox has experimental support for Mac OS X guests. This allows
you to install and execute unmodified versions of Mac OS X on supported host hardware.
Whereas competing solutions perform modifications to the Mac OS X install DVDs (e.g. different boot loader and replaced files), VirtualBox is the first product to provide the modern PC
architecture expected by OS X without requiring any “hacks”.
You should be aware of a number of important issues before attempting to install a Mac OS
X guest:
1. Mac OS X is commercial, licensed software and contains both license and technical restrictions that limit its use to certain hardware and usage scenarios. It is important that
you understand and obey these restrictions.
In particular, for most versions of Mac OS X, Apple prohibits installing them on non-Apple
hardware.
These license restrictions are also enforced on a technical level. Mac OS X verifies whether
it is running on Apple hardware, and most DVDs that that come with Apple hardware
even check for an exact model. These restrictions are not circumvented by VirtualBox and
continue to apply.
2. Only CPUs known and tested by Apple are supported. As a result, if your Intel CPU is
newer than the build of Mac OS X, or if you have a non-Intel CPU, it will most likely panic
during bootup with an “Unsupported CPU” exception. It is generally best to use the Mac
OS X DVD that came with your Apple hardware.
3. The Mac OS X installer expects the harddisk to be partitioned so when it does not offer a
selection, you have to launch the Disk Utility from the “Tools” menu and partition the hard
disk. Then close the Disk Utility and proceed with the installation.
4. In addition, as Mac OS X support in VirtualBox is currently still experimental, please refer
also to chapter 14, Known limitations, page 229.

3.1.2 64-bit guests
VirtualBox supports 64-bit guest operating systems, even on 32-bit host operating systems,2 provided that the following conditions are met:
1. You need a 64-bit processor with hardware virtualization support (see chapter 10.3, Hardware vs. software virtualization, page 202).
2. You must enable hardware virtualization for the particular VM for which you want 64-bit
support; software virtualization is not supported for 64-bit VMs.
1 See

chapter 14, Known limitations, page 229.
guest support was added with VirtualBox 2.0; support for 64-bit guests on 32-bit hosts was added with
VirtualBox 2.1.

2 64-bit

3 Configuring virtual machines
3. If you want to use 64-bit guest support on a 32-bit host operating system, you must also
select a 64-bit operating system for the particular VM. Since supporting 64 bits on 32bit hosts incurs additional overhead, VirtualBox only enables this support upon explicit
request.
On 64-bit hosts (which typically come with hardware virtualization support), 64-bit guest
operating systems are always supported regardless of settings, so you can simply install a
64-bit operating system in the guest.

Warning: On any host, you should enable the I/O APIC for virtual machines that
you intend to use in 64-bit mode. This is especially true for 64-bit Windows VMs.
See chapter 3.3.2, “Advanced” tab, page 48. In addition, for 64-bit Windows guests,
you should make sure that the VM uses the Intel networking device, since there is
no 64-bit driver support for the AMD PCNet card; see chapter 6.1, Virtual networking
hardware, page 92.
If you use the “Create VM” wizard of the VirtualBox graphical user interface (see chapter
1.7, Creating your first virtual machine, page 18), VirtualBox will automatically use the correct
settings for each selected 64-bit operating system type.

3.2 Emulated hardware
VirtualBox virtualizes nearly all hardware of the host. Depending on a VM’s configuration, the
guest will see the following virtual hardware:
• Input devices. By default, VirtualBox emulates a standard PS/2 keyboard and mouse.
These devices are supported by almost all past and present operating systems.
In addition, VirtualBox can provide virtual USB input devices to avoid having to capture
mouse and keyboard, as described in chapter 1.8.2, Capturing and releasing keyboard and
mouse, page 22.
• Graphics. The VirtualBox graphics device (sometimes referred to as VGA device) is, unlike
nearly all other emulated devices, not based on any physical counterpart. It is a simple,
synthetic device which provides compatibility with standard VGA and several extended
registers used by the VESA BIOS Extensions (VBE).
• Storage. VirtualBox currently emulates the standard ATA interface found on Intel
PIIX3/PIIX4 chips, the SATA (AHCI) interface, and two SCSI adapters (LSI Logic and BusLogic); see chapter 5.1, Hard disk controllers: IDE, SATA (AHCI), SCSI, SAS, page 80 for
details. Whereas providing one of these would be enough for VirtualBox by itself, this multitude of storage adapters is required for compatibility with other hypervisors. Windows is
particularly picky about its boot devices, and migrating VMs between hypervisors is very
difficult or impossible if the storage controllers are different.
• Networking. See chapter 6.1, Virtual networking hardware, page 92.
• USB. VirtualBox emulates two USB host controllers, EHCI and OHCI. There is a need for
two host controllers because OHCI only handles USB low- and full-speed devices (both USB
1.x and 2.0), while EHCI only handles high-speed devices (USB 2.0 only). The emulated
USB controllers do not communicate directly with devices on the host but rather with a
virtual USB layer which abstracts the USB protocol and allows the use of remote USB
devices.
• Audio. See chapter 3.7, Audio settings, page 54.

3 Configuring virtual machines

3.3 General settings
In the Settings window, under “General”, you can configure the most fundamental aspects of
the virtual machine such as memory and essential hardware. There are three tabs, “Basic”,
“Advanced” and “Description”.

3.3.1 “Basic” tab
Under the “Basic” tab of the “General” settings category, you can find these settings:
Name The name under which the VM is shown in the list of VMs in the main window. Under this
name, VirtualBox also saves the VM’s configuration files. By changing the name, VirtualBox
renames these files as well. As a result, you can only use characters which are allowed in
your host operating system’s file names.
Note that internally, VirtualBox uses unique identifiers (UUIDs) to identify virtual machines. You can display these with VBoxManage.
Operating system / version The type of the guest operating system that is (or will be) installed
in the VM. This is the same setting that was specified in the “New Virtual Machine” wizard,
as described in chapter 1.7, Creating your first virtual machine, page 18.
Whereas the default settings of a newly created VM depend on the selected operating
system type, changing the type later has no effect on VM settings; this value is then purely
informational and decorative.

3.3.2 “Advanced” tab
Snapshot folder By default, VirtualBox saves snapshot data together with your other VirtualBox
configuration data; see chapter 10.1, Where VirtualBox stores its files, page 198. With this
setting, you can specify any other folder for each VM.
Shared clipboard You can select here whether the clipboard of the guest operating system
should be shared with that of your host. If you select “Bidirectional”, then VirtualBox will
always make sure that both clipboards contain the same data. If you select “Host to guest”
or “Guest to host”, then VirtualBox will only ever copy clipboard data in one direction.
Clipboard sharing requires that the VirtualBox Guest Additions be installed. As a result,
this setting has no effect otherwise; see chapter 4, Guest Additions, page 60 for details.
The shared clipboard is disabled by default. See chapter 13.3.2.3, Clipboard, page 227
for an explanation. This setting can be changed at any time using the “Shared Clipboard”
menu item in the “Devices” menu of the virtual machine.
Drag’n’Drop This setting allows to enable Drag and Drop: Select a file on the desktop, click the
left mouse button, move the mouse to the VM window and release the mouse button. The
file is copied from the host to the guest. This feature is currently only implemented for
Linux guests and only for copying files from the host to the guest.3
Removable media: remember runtime changes If this is checked, VirtualBox will save the
state of what media has been mounted between several runs of a virtual machine.
Mini toolbar In full screen or seamless mode, VirtualBox can display a small toolbar that contains some of the items that are normally available from the virtual machine’s menu bar.
This toolbar reduces itself to a small gray line unless you move the mouse over it. With the
toolbar, you can return from full screen or seamless mode, control machine execution or
enable certain devices. If you don’t want to see the toolbar, disable this setting.
3 Support

for Drag’n’Drop was added with VirtualBox 4.2

3 Configuring virtual machines
The second setting allows to show the toolbar at the top of the screen instead of showing
it at the bottom.

3.3.3 “Description” tab
Here you can enter any description for your virtual machine, if you want. This has no effect on
the functionality of the machine, but you may find this space useful to note down things like the
configuration of a virtual machine and the software that has been installed into it.
To insert a line break into the description text field, press Shift+Enter.

3.4 System settings
The “System” category groups various settings that are related to the basic hardware that is
presented to the virtual machine.
Note: As the activation mechanism of Microsoft Windows is sensitive to hardware
changes, if you are changing hardware settings for a Windows guest, some of these
changes may trigger a request for another activation with Microsoft.

3.4.1 “Motherboard” tab
On the “Motherboard” tab, you can influence virtual hardware that would normally be on the
motherboard of a real computer.
Base memory This sets the amount of RAM that is allocated and given to the VM when it is
running. The specified amount of memory will be requested from the host operating system, so it must be available or made available as free memory on the host when attempting
to start the VM and will not be available to the host while the VM is running. This is the
same setting that was specified in the “New Virtual Machine” wizard, as described with
guidelines under chapter 1.7, Creating your first virtual machine, page 18 above.
Generally, it is possible to change the memory size after installing the guest operating
system (provided you do not reduce the memory to an amount where the operating system
would no longer boot).
Boot order This setting determines the order in which the guest operating system will attempt
to boot from the various virtual boot devices. Analogous to a real PC’s BIOS setting,
VirtualBox can tell a guest OS to start from the virtual floppy, the virtual CD/DVD drive,
the virtual hard drive (each of these as defined by the other VM settings), the network, or
none of these.
If you select “Network”, the VM will attempt to boot from a network via the PXE mechanism. This needs to be configured in detail on the command line; please see chapter 8.8,
VBoxManage modifyvm, page 125.
Chipset Here you can select which chipset will be presented to the virtual machine. Before
VirtualBox 4.0, PIIX3 was the only available option here. For modern guest operating systems such as Mac OS X, that old chipset is no longer well supported. As a result, VirtualBox
4.0 introduced an emulation of the more modern ICH9 chipset, which supports PCI express, three PCI buses, PCI-to-PCI bridges and Message Signaled Interrupts (MSI). This
allows modern operating systems to address more PCI devices and no longer requires IRQ
sharing. Note that the ICH9 support is experimental and not recommended for guest operating systems which do not require it.

3 Configuring virtual machines
Pointing Device The default virtual pointing devices for older guests is the traditional PS/2
mouse. If set to USB tablet, VirtualBox reports to the virtual machine that a USB tablet
device is present and communicates mouse events to the virtual machine through this
device. The third setting is a USB Multi-Touch Tablet which is suited for recent Windows
guests.
Using the virtual USB tablet has the advantage that movements are reported in absolute
coordinates (instead of as relative position changes), which allows VirtualBox to translate
mouse events over the VM window into tablet events without having to “capture” the
mouse in the guest as described in chapter 1.8.2, Capturing and releasing keyboard and
mouse, page 22. This makes using the VM less tedious even if Guest Additions are not
installed.4
Enable I/O APIC Advanced Programmable Interrupt Controllers (APICs) are a newer x86 hardware feature that have replaced old-style Programmable Interrupt Controllers (PICs) in
recent years. With an I/O APIC, operating systems can use more than 16 interrupt requests
(IRQs) and therefore avoid IRQ sharing for improved reliability.
Note: Enabling the I/O APIC is required for 64-bit guest operating systems, especially
Windows Vista; it is also required if you want to use more than one virtual CPU in a
virtual machine.
However, software support for I/O APICs has been unreliable with some operating systems other than Windows. Also, the use of an I/O APIC slightly increases the overhead of
virtualization and therefore slows down the guest OS a little.
Warning: All Windows operating systems starting with Windows 2000 install different
kernels depending on whether an I/O APIC is available. As with ACPI, the I/O APIC
therefore must not be turned off after installation of a Windows guest OS. Turning it on
after installation will have no effect however.
Enable EFI This enables Extensible Firmware Interface (EFI), which replaces the legacy BIOS
and may be useful for certain advanced use cases. Please refer to chapter 3.12, Alternative
firmware (EFI), page 58 for details.
Hardware clock in UTC time If checked, VirtualBox will report the system time in UTC format
to the guest instead of local (host) time. This affects how the virtual real-time clock (RTC)
operates and may be useful for Unix-like guest operating systems, which typically expect
the hardware clock to be set to UTC.
In addition, you can turn off the Advanced Configuration and Power Interface (ACPI) which
VirtualBox presents to the guest operating system by default. ACPI is the current industry standard to allow operating systems to recognize hardware, configure motherboards and other devices and manage power. As all modern PCs contain this feature and Windows and Linux have
been supporting it for years, it is also enabled by default in VirtualBox. It can only be turned off
on the command line; see chapter 8.8, VBoxManage modifyvm, page 125.
Warning: All Windows operating systems starting with Windows 2000 install different
kernels depending on whether ACPI is available, so ACPI must not be turned off after
installation of a Windows guest OS. Turning it on after installation will have no effect
however.
4 The

virtual USB tablet was added with VirtualBox 3.2. Depending on the guest operating system selected, this is now
enabled by default for new virtual machines.

3 Configuring virtual machines

3.4.2 “Processor” tab
On the “Processor” tab, you can set how many virtual CPU cores the guest operating systems
should see. Starting with version 3.0, VirtualBox supports symmetrical multiprocessing (SMP)
and can present up to 32 virtual CPU cores to each virtual machine.
You should not, however, configure virtual machines to use more CPU cores than you have
available physically (real cores, no hyperthreads).
On this tab you can also set the “CPU execution cap”. This setting limits the amount of time
a host CPU spents to emulate a virtual CPU. The default setting is 100% meaning that there is no
limitation. A setting of 50% implies a single virtual CPU can use up to 50% of a single host CPU.
Note that limiting the execution time of the virtual CPUs may induce guest timing problems.
In addition, the “Enable PAE/NX” setting determines whether the PAE and NX capabilities of
the host CPU will be exposed to the virtual machine. PAE stands for “Physical Address Extension”.
Normally, if enabled and supported by the operating system, then even a 32-bit x86 CPU can
access more than 4 GB of RAM. This is made possible by adding another 4 bits to memory
addresses, so that with 36 bits, up to 64 GB can be addressed. Some operating systems (such
as Ubuntu Server) require PAE support from the CPU and cannot be run in a virtual machine
without it.
With virtual machines running modern server operating systems, VirtualBox also supports CPU
hot-plugging. For details about this, please refer to chapter 9.5, CPU hot-plugging, page 166.

3.4.3 “Acceleration” tab
On this page, you can determine whether and how VirtualBox should use hardware virtualization
extensions that your host CPU may support. This is the case with most CPUs built after 2006.
You can select for each virtual machine individually whether VirtualBox should use software
or hardware virtualization.5
In most cases, the default settings will be fine; VirtualBox will have picked sensible defaults
depending on the operating system that you selected when you created the virtual machine. In
certain situations, however, you may want to change these preconfigured defaults.
Advanced users may be interested in technical details about software vs. hardware virtualization; please see chapter 10.3, Hardware vs. software virtualization, page 202.
If your host’s CPU supports the nested paging (AMD-V) or EPT (Intel VT-x) features, then you
can expect a significant performance increase by enabling nested paging in addition to hardware
virtualization. For technical details, see chapter 10.6, Nested paging and VPIDs, page 206.

3.5 Display settings
Video memory size This sets the size of the memory provided by the virtual graphics card
available to the guest, in MB. As with the main memory, the specified amount will be
allocated from the host’s resident memory. Based on the amount of video memory, higher
resolutions and color depths may be available.
The GUI will show a warning if the amount of video memory is too small to be able to
switch the VM into full screen mode. The minimum value depends on the number of
virtual monitors, the screen resolution and the color depth of the host display as well as
of the activation of 3D acceleration and 2D video acceleration. A rough estimate is (color
depth / 8) x vertical pixels x horizontal pixels x number of screens = number of bytes. Like
said above, there might be extra memory required for any activated display acceleration
setting.
5 Prior

to VirtualBox version 2.2, software virtualization was the default; starting with version 2.2, VirtualBox will
enable hardware virtualization by default for new virtual machines that you create. (Existing virtual machines are not
automatically changed for compatibility reasons, and the default can of course be changed for each virtual machine.)

3 Configuring virtual machines
Monitor count With this setting VirtualBox can provide more than one virtual monitor to a
virtual machine. If a guest operating system (such as Windows) supports multiple attached
monitors, VirtualBox can pretend that multiple virtual monitors are present.6 Up to 8 such
virtual monitors are supported.
The output of the multiple monitors will be displayed on the host in multiple VM windows
which are running side by side.
However, in full screen and seamless mode, they will use the available physical monitors
attached to the host. As a result, for full screen and seamless modes to work with multiple
monitors, you will need at least as many physical monitors as you have virtual monitors
configured, or VirtualBox will report an error. You can configure the relationship between
guest and host monitors using the view menu by pressing Host key + Home when you are
in full screen or seamless mode.
Please see chapter 14, Known limitations, page 229 also.
Enable 3D acceleration If a virtual machine has Guest Additions installed, you can select here
whether the guest should support accelerated 3D graphics. Please refer to chapter 4.4.1,
Hardware 3D acceleration (OpenGL and Direct3D 8/9), page 73 for details.
Enable 2D video acceleration If a virtual machine with Microsoft Windows has Guest Additions installed, you can select here whether the guest should support accelerated 2D video
graphics. Please refer to chapter 4.4.2, Hardware 2D video acceleration for Windows guests,
page 74 for details.
Remote display Under the “Remote display” tab, if the VirtualBox Remote Display Extension
(VRDE) is installed, you can enable the VRDP server that is built into VirtualBox. This
allows you to connect to the console of the virtual machine remotely with any standard
RDP viewer, such as mstsc.exe that comes with Microsoft Windows. On Linux and Solaris
systems you can use the standard open-source rdesktop program. These features are
described in detail in chapter 7.1, Remote display (VRDP support), page 103.
Video Capture Under the “Video Capture” tab you can enable video capturing for this VM. Note
that this feature can also be enabled/disabled while the VM is executed.

3.6 Storage settings
The “Storage” category in the VM settings allows you to connect virtual hard disk, CD/DVD and
floppy images and drives to your virtual machine.
In a real PC, so-called “storage controllers” connect physical disk drives to the rest of the computer. Similarly, VirtualBox presents virtual storage controllers to a virtual machine. Under each
controller, the virtual devices (hard disks, CD/DVD or floppy drives) attached to the controller
are shown.
Note: This section can only give you a quick introduction to the VirtualBox storage
settings. Since VirtualBox gives you an enormous wealth of options in this area, we
have dedicated an entire chapter of this User Manual to explaining all the details:
please see chapter 5, Virtual storage, page 80.
If you have used the “Create VM” wizard to create a machine, you will normally see something
like the following:

6 Multiple

monitor support was added with VirtualBox 3.2.

3 Configuring virtual machines

Depending on the guest operating system type that you selected when you created the VM, the
typical layout of storage devices in a new VM is as follows:
• You will see an IDE controller, to which a virtual CD/DVD drive has been attached (to the
“secondary master” port of the IDE controller).
• You will also see a SATA controller, which is a more modern type of storage controller for
higher hard disk data throughput, to which the virtual hard disks are attached. Initially
you will normally have one such virtual disk, but as you can see in the above screenshot,
you can have more than one, each represented by a disk image file (VDI files, in this case).
If you created your VM with an older version of VirtualBox, the default storage layout may
differ. You might then only have an IDE controller to which both the CD/DVD drive and the hard
disks have been attached. This might also apply if you selected an older operating system type
when you created the VM. Since older operating systems do not support SATA without additional
drivers, VirtualBox will make sure that no such devices are present initially. Please see chapter
5.1, Hard disk controllers: IDE, SATA (AHCI), SCSI, SAS, page 80 for additional information.
VirtualBox also provides a floppy controller, which is special: you cannot add devices other
than floppy drives to it. Virtual floppy drives, like virtual CD/DVD drives, can be connected to
either a host floppy drive (if you have one) or a disk image, which in this case must be in RAW
format.
You can modify these media attachments freely. For example, if you wish to copy some files
from another virtual disk that you created, you can connect that disk as a second hard disk, as in
the above screenshot. You could also add a second virtual CD/DVD drive, or change where these
items are attached. The following options are available:
• To add another virtual hard disk, or a CD/DVD or floppy drive, select the storage controller to which it should be added (IDE, SATA, SCSI, SAS, floppy controller) and then click
on the “add disk” button below the tree. You can then either select “Add CD/DVD device”
or “Add Hard Disk”. (If you clicked on a floppy controller, you can add a floppy drive
instead.) Alternatively, right-click on the storage controller and select a menu item there.
On the right part of the window, you can then set the following:
1. You can then select to which device slot of the controller the virtual disk should be
connected to. IDE controllers have four slots which have traditionally been called

3 Configuring virtual machines
“primary master”, “primary slave”, “secondary master” and “secondary slave”. By
contrast, SATA and SCSI controllers offer you up to 30 slots to which virtual devices
can be attached.
2. You can select which image file to use.
– For virtual hard disks, a button with a drop-down list appears on the right, offering you to either select a virtual hard disk file using a standard file dialog or to
create a new hard disk (image file), which will bring up the “Create new disk”
wizard, which was described in chapter 1.7, Creating your first virtual machine,
page 18.
For details on the image file types that are supported, please see chapter 5.2, Disk
image files (VDI, VMDK, VHD, HDD), page 82.
– For virtual CD/DVD drives, the image files will typically be in the standard ISO
format instead. Most commonly, you will select this option when installing an
operating system from an ISO file that you have obtained from the Internet. For
example, most Linux distributions are available in this way.
For virtual CD/DVD drives, the following additional options are available:
∗ If you select “Host drive” from the list, then the physical device of the host
computer is connected to the VM, so that the guest operating system can read
from and write to your physical device. This is, for instance, useful if you
want to install Windows from a real installation CD. In this case, select your
host drive from the drop-down list presented.
If you want to write (burn) CDs or DVDs using the host drive, you need to also
enable the “Passthrough” option; see chapter 5.9, CD/DVD support, page 90.
∗ If you select “Remove disk from virtual drive”, VirtualBox will present an
empty CD/DVD drive to the guest into which no media has been inserted.
• To remove an attachment, select it and click on the “remove” icon at the bottom (or
right-click on it and select the menu item).
Removable media (CD/DVDs and floppies) can be changed while the guest is running. Since
the “Settings” dialog is not available at that time, you can also access these settings from the
“Devices” menu of your virtual machine window.

3.7 Audio settings
The “Audio” section in a virtual machine’s Settings window determines whether the VM will see
a sound card connected, and whether the audio output should be heard on the host system.
If audio is enabled for a guest, you can choose between the emulation of an Intel AC’97
controller, an Intel HD Audio controller7 or a SoundBlaster 16 card. In any case, you can select
what audio driver VirtualBox will use on the host.
On a Linux host, depending on your host configuration, you can also select between the OSS,
ALSA or the PulseAudio subsystem. On newer Linux distributions (Fedora 8 and above, Ubuntu
8.04 and above), the PulseAudio subsystem should be preferred.

3.8 Network settings
The “Network” section in a virtual machine’s Settings window allows you to configure how
VirtualBox presents virtual network cards to your VM, and how they operate.
7 Intel

HD Audio support was added with VirtualBox 4.0 because Windows 7 (32-bit and 64-bit versions) as well as
64-bit Windows Vista do not support the Intel AC’97 controller.

3 Configuring virtual machines
When you first create a virtual machine, VirtualBox by default enables one virtual network
card and selects the “Network Address Translation” (NAT) mode for it. This way the guest can
connect to the outside world using the host’s networking and the outside world can connect to
services on the guest which you choose to make visible outside of the virtual machine.
This default setup is good for probably 95% of VirtualBox users. However, VirtualBox is extremely flexible in how it can virtualize networking. It supports many virtual network cards
per virtual machine, the first four of which can be configured in detail in the Manager window.
Additional network cards can be configured on the command line with VBoxManage.
Because of the vast array of options available, we have dedicated an entire chapter of this
manual to discussing networking configuration; please see chapter 6, Virtual networking, page
92.

3.9 Serial ports
VirtualBox fully supports virtual serial ports in a virtual machine in an easy-to-use manner.8
Ever since the original IBM PC, personal computers have been equipped with one or two serial
ports (also called COM ports by DOS and Windows). Serial ports were commonly used with
modems, and some computer mice used to be connected to serial ports before USB became
commonplace.
While serial ports are no longer as ubiquitous as they used to be, there are still some important
uses left for them. For example, serial ports can be used to set up a primitive network over a nullmodem cable, in case Ethernet is not available. Also, serial ports are indispensable for system
programmers needing to do kernel debugging, since kernel debugging software usually interacts
with developers over a serial port. With virtual serial ports, system programmers can do kernel
debugging on a virtual machine instead of needing a real computer to connect to.
If a virtual serial port is enabled, the guest operating system sees a standard 16550A compatible UART device. Both receiving and transmitting data is supported. How this virtual serial
port is then connected to the host is configurable, and the details depend on your host operating
system.
You can use either the graphical user interface or the command-line VBoxManage tool to set up
virtual serial ports. For the latter, please refer to chapter 8.8, VBoxManage modifyvm, page 125;
in that section, look for the --uart and --uartmode options.
In either case, you can configure up to two virtual serial ports per virtual machine. For each
such device, you will need to determine
1. what kind of serial port the virtual machine should see by selecting an I/O base address
and interrupt (IRQ). For these, we recommend to use the traditional values9 , which are:
a) COM1: I/O base 0x3F8, IRQ 4
b) COM2: I/O base 0x2F8, IRQ 3
c) COM3: I/O base 0x3E8, IRQ 4
d) COM4: I/O base 0x2E8, IRQ 3
2. Then, you will need to determine what this virtual port should be connected to. For each
virtual serial port, you have the following options:
• You can elect to have the virtual serial port “disconnected”, which means that the
guest will see the device, but it will behave as if no cable had been connected to it.
• You can connect the virtual serial port to a physical serial port on your host. (On a
Windows host, this will be a name like COM1; on Linux or Solaris hosts, it will be a
device node like /dev/ttyS0). VirtualBox will then simply redirect all data received
from and sent to the virtual serial port to the physical device.
8 Serial
9 See,

port support was added with VirtualBox 1.5.
for example, http://en.wikipedia.org/wiki/COM_(hardware_interface).

3 Configuring virtual machines
• You can tell VirtualBox to connect the virtual serial port to a software pipe on the host.
This depends on your host operating system:
– On a Windows host, data will be sent and received through a named pipe. The
pipe name must be in the format \\.\pipe\ where should identify the virtual machine but may be freely chosen.
For forwarding serial traffic, you can use a helper program called VMware Serial
Line Gateway, available for download at http://www.l4ka.org/91.php. This
tool provides a fixed server mode named pipe at \\.\pipe\vmwaredebug and
connects incoming TCP connections on port 567 with the named pipe.
– On a Mac, Linux or Solaris host, a local domain socket is used instead. The socket
filename must be chosen such that the user running VirtualBox has sufficient
privileges to create and write to it. The /tmp directory is often a good candidate.
On Linux there are various tools which can connect to a local domain socket or
create one in server mode. The most flexible tool is socat and is available as part
of many distributions.
In this case, you can configure whether VirtualBox should create the named pipe (or,
on non-Windows hosts, the local domain socket) itself or whether VirtualBox should
assume that the pipe (or socket) exists already. With the VBoxManage command-line
options, this is referred to as “server” or “client” mode, respectively.
For a direct connection between two virtual machines (corresponding to a null-modem
cable), simply configure one VM to create a pipe/socket and another to attach to it.
• You can send the virtual serial port output to a file. This option is very useful for
capturing diagnostic output from a guest. Any file may be used for this purpose, as
long as the user running VirtualBox has sufficient privileges to create and write to the
file.
Up to two serial ports can be configured per virtual machine, but you can pick any port numbers
out of the above. However, serial ports cannot reliably share interrupts; if both ports are to be
used at the same time, they must use different interrupt levels, for example COM1 and COM2,
but not COM1 and COM3.

3.10 USB support
3.10.1 USB settings
The “USB” section in a virtual machine’s Settings window allows you to configure VirtualBox’s
sophisticated USB support.
VirtualBox can allow virtual machines to access the USB devices on your host directly. To
achieve this, VirtualBox presents the guest operating system with a virtual USB controller. As
soon as the guest system starts using a USB device, it will appear as unavailable on the host.
Note:
1. Be careful with USB devices that are currently in use on the host! For example, if
you allow your guest to connect to your USB hard disk that is currently mounted
on the host, when the guest is activated, it will be disconnected from the host
without a proper shutdown. This may cause data loss.
2. Solaris hosts have a few known limitations regarding USB support; please see
chapter 14, Known limitations, page 229.

3 Configuring virtual machines
In addition to allowing a guest access to your local USB devices, VirtualBox even allows your
guests to connect to remote USB devices by use of the VirtualBox Remote Desktop Extension
(VRDE). For details about this, see chapter 7.1.4, Remote USB, page 107.
In the Settings dialog, you can first configure whether USB is available in the guest at all, and
in addition also optionally enable the USB 2.0 (EHCI) controller for the guest. If so, you can
determine in detail which devices are available. For this, you must create so-called “filters” by
specifying certain properties of the USB device.
Note: The EHCI controller is shipped as a VirtualBox extension package, which must
be installed separately. See chapter 1.5, Installing VirtualBox and extension packs, page
16 for more information.
Clicking on the “+“ button to the right of the “USB Device Filters” window creates a new filter.
You can give the filter a name (for referencing it later) and specify the filter criteria. The more
criteria you specify, the more precisely devices will be selected. For instance, if you specify only
a vendor ID of 046d, all devices produced by Logitech will be available to the guest. If you fill
in all fields, on the other hand, the filter will only apply to a particular device model from a
particular vendor, and not even to other devices of the same type with a different revision and
serial number.
In detail, the following criteria are available:
1. Vendor and product ID. With USB, each vendor of USB products carries an identification
number that is unique world-wide, the “vendor ID”. Similarly, each line of products is
assigned a “product ID” number. Both numbers are commonly written in hexadecimal
(that is, they are composed of the numbers 0-9 and the letters A-F), and a colon separates
the vendor from the product ID. For example, 046d:c016 stands for Logitech as a vendor,
and the “M-UV69a Optical Wheel Mouse” product.
Alternatively, you can also specify “Manufacturer” and “Product” by name.
To list all the USB devices that are connected to your host machine with their respective
vendor and product IDs, you can use the following command (see chapter 8, VBoxManage,
page 113):
VBoxManage list usbhost

On Windows, you can also see all USB devices that are attached to your system in the
Device Manager. On Linux, you can use the lsusb command.
2. Serial number. While vendor and product ID are already quite specific to identify USB
devices, if you have two identical devices of the same brand and product line, you will also
need their serial numbers to filter them out correctly.
3. Remote. This setting specifies whether the device will be local only, or remote only (over
VRDP), or either.
On a Windows host, you will need to unplug and reconnect a USB device to use it after creating
a filter for it.
As an example, you could create a new USB filter and specify a vendor ID of 046d (Logitech,
Inc), a manufacturer index of 1, and “not remote”. Then any USB devices on the host system
produced by Logitech, Inc with a manufacturer index of 1 will be visible to the guest system.
Several filters can select a single device – for example, a filter which selects all Logitech devices,
and one which selects a particular webcam.
You can deactivate filters without deleting them by clicking in the checkbox next to the filter
name.

3 Configuring virtual machines

3.10.2 Implementation notes for Windows and Linux hosts
On Windows hosts, a kernel mode device driver provides USB proxy support. It implements both
a USB monitor, which allows VirtualBox to capture devices when they are plugged in, and a USB
device driver to claim USB devices for a particular virtual machine. As opposed to VirtualBox
versions before 1.4.0, system reboots are no longer necessary after installing the driver. Also,
you no longer need to replug devices for VirtualBox to claim them.
On newer Linux hosts, VirtualBox accesses USB devices through special files in the file system.
When VirtualBox is installed, these are made available to all users in the vboxusers system
group. In order to be able to access USB from guest systems, make sure that you are a member
of this group.
On older Linux hosts, USB devices are accessed using the usbfs file system. Therefore, the
user executing VirtualBox needs read and write permission to the USB file system. Most distributions provide a group (e.g. usbusers) which the VirtualBox user needs to be added to. Also,
VirtualBox can only proxy to virtual machines USB devices which are not claimed by a Linux
host USB driver. The Driver= entry in /proc/bus/usb/devices will show you which devices
are currently claimed. Please refer to chapter 12.7.7, USB not working, page 223 also for details
about usbfs.

3.11 Shared folders
Shared folders allow you to easily exchange data between a virtual machine and your host. This
feature requires that the VirtualBox Guest Additions be installed in a virtual machine and is
described in detail in chapter 4.3, Shared folders, page 70.

3.12 Alternative firmware (EFI)
Starting with release 3.1, VirtualBox includes experimental support for the Extensible Firmware
Interface (EFI), which is a new industry standard intended to eventually replace the legacy BIOS
as the primary interface for bootstrapping computers and certain system services later.
By default, VirtualBox uses the BIOS firmware for virtual machines. To use EFI for a given
virtual machine, you can enable EFI in the machine’s “Settings” dialog (see chapter 3.4.1, “Motherboard” tab, page 49). Alternatively, use the VBoxManage command line interface like this:
VBoxManage modifyvm "VM name" --firmware efi

To switch back to using the BIOS, use:
VBoxManage modifyvm "VM name" --firmware bios

One notable user of EFI is Apple’s Mac OS X, but recent Linuxes (such as Fedora 11) and Windows
(starting with Vista) offer special versions that can be booted using EFI as well.
Another possible use of EFI in VirtualBox is development and testing of EFI applications, without booting any OS.
Note that the VirtualBox EFI support is experimental and will be enhanced as EFI matures and
becomes more widespread. While Mac OS X and Linux guests are known to work fine, Windows
guests are currently unable to boot with the VirtualBox EFI implementation.

3.12.1 Video modes in EFI
EFI provides two distinct video interfaces: GOP (Graphics Output Protocol) and UGA (Universal
Graphics Adapter). Mac OS X uses GOP, while Linux tends to use UGA. VirtualBox provides a
configuration option to control the framebuffer size for both interfaces.
To control GOP, use the following VBoxManage command:

3 Configuring virtual machines
VBoxManage setextradata "VM name" VBoxInternal2/EfiGopMode N

Where N can be one of 0,1,2,3,4,5 referring to the 640x480, 800x600, 1024x768, 1280x1024,
1440x900, 1920x1200 screen resolution respectively.
To change the UGA resolution:
VBoxManage setextradata "VM name" VBoxInternal2/UgaHorizontalResolution 1440
VBoxManage setextradata "VM name" VBoxInternal2/UgaVerticalResolution
900

The video mode for both GOP and UGA can only be changed when the VM is powered off and
remains persistent until changed.

3.12.2 Specifying boot arguments
It is currently not possible to manipulate EFI variables from within a running guest (e.g., setting
the “boot-args” variable by running the nvram tool in a Mac OS X guest will not work). As an
alternative way, “VBoxInternal2/EfiBootArgs” extradata can be passed to a VM in order to set the
“boot-args” variable. To change the “boot-args” EFI variable:
VBoxManage setextradata "VM name" VBoxInternal2/EfiBootArgs

4 Guest Additions
The previous chapter covered getting started with VirtualBox and installing operating systems in
a virtual machine. For any serious and interactive use, the VirtualBox Guest Additions will make
your life much easier by providing closer integration between host and guest and improving the
interactive performance of guest systems. This chapter describes the Guest Additions in detail.

4.1 Introduction
As mentioned in chapter 1.2, Some terminology, page 12, the Guest Additions are designed to
be installed inside a virtual machine after the guest operating system has been installed. They
consist of device drivers and system applications that optimize the guest operating system for
better performance and usability. Please see chapter 3.1, Supported guest operating systems, page
45 for details on what guest operating systems are fully supported with Guest Additions by
VirtualBox.
The VirtualBox Guest Additions for all supported guest operating systems are provided as a
single CD-ROM image file which is called VBoxGuestAdditions.iso. This image file is located
in the installation directory of VirtualBox. To install the Guest Additions for a particular VM, you
mount this ISO file in your VM as a virtual CD-ROM and install from there.
The Guest Additions offer the following features:
Mouse pointer integration To overcome the limitations for mouse support that were described
in chapter 1.8.2, Capturing and releasing keyboard and mouse, page 22, this provides you
with seamless mouse support. You will only have one mouse pointer and pressing the Host
key is no longer required to “free” the mouse from being captured by the guest OS. To
make this work, a special mouse driver is installed in the guest that communicates with the
“real” mouse driver on your host and moves the guest mouse pointer accordingly.
Shared folders These provide an easy way to exchange files between the host and the guest.
Much like ordinary Windows network shares, you can tell VirtualBox to treat a certain host
directory as a shared folder, and VirtualBox will make it available to the guest operating
system as a network share, irrespective of whether guest actually has a network. For details,
please refer to chapter 4.3, Shared folders, page 70.
Better video support While the virtual graphics card which VirtualBox emulates for any guest
operating system provides all the basic features, the custom video drivers that are installed
with the Guest Additions provide you with extra high and non-standard video modes as
well as accelerated video performance.
In addition, with Windows, Linux and Solaris guests, you can resize the virtual machine’s
window if the Guest Additions are installed. The video resolution in the guest will be automatically adjusted (as if you had manually entered an arbitrary resolution in the guest’s
display settings). Please see chapter 1.8.5, Resizing the machine’s window, page 24 also.
Finally, if the Guest Additions are installed, 3D graphics and 2D video for guest applications
can be accelerated; see chapter 4.4, Hardware-accelerated graphics, page 73.
Seamless windows With this feature, the individual windows that are displayed on the desktop
of the virtual machine can be mapped on the host’s desktop, as if the underlying application
was actually running on the host. See chapter 4.5, Seamless windows, page 74 for details.

4 Guest Additions
Generic host/guest communication channels The Guest Additions enable you to control and
monitor guest execution in ways other than those mentioned above. The so-called “guest
properties” provide a generic string-based mechanism to exchange data bits between a
guest and a host, some of which have special meanings for controlling and monitoring the
guest; see chapter 4.6, Guest properties, page 75 for details.
Additionally, applications can be started in a guest from the host; see chapter 4.7, Guest
control, page 77.
Time synchronization With the Guest Additions installed, VirtualBox can ensure that the
guest’s system time is better synchronized with that of the host.
For various reasons, the time in the guest might run at a slightly different rate than the
time on the host. The host could be receiving updates via NTP and its own time might not
run linearly. A VM could also be paused, which stops the flow of time in the guest for a
shorter or longer period of time. When the wall clock time between the guest and host only
differs slightly, the time synchronization service attempts to gradually and smoothly adjust
the guest time in small increments to either “catch up” or “lose” time. When the difference
is too great (e.g., a VM paused for hours or restored from saved state), the guest time is
changed immediately, without a gradual adjustment.
The Guest Additions will re-synchronize the time regularly. See chapter 9.14.3, Tuning
the Guest Additions time synchronization parameters, page 179 for how to configure the
parameters of the time synchronization mechanism.
Shared clipboard With the Guest Additions installed, the clipboard of the guest operating system can optionally be shared with your host operating system; see chapter 3.3, General
settings, page 48.
Automated logons (credentials passing) For details, please see chapter 9.2, Automated guest
logons, page 160.
Each version of VirtualBox, even minor releases, ship with their own version of the Guest
Additions. While the interfaces through which the VirtualBox core communicates with the Guest
Additions are kept stable so that Guest Additions already installed in a VM should continue to
work when VirtualBox is upgraded on the host, for best results, it is recommended to keep the
Guest Additions at the same version.
Starting with VirtualBox 3.1, the Windows and Linux Guest Additions therefore check automatically whether they have to be updated. If the host is running a newer VirtualBox version
than the Guest Additions, a notification with further instructions is displayed in the guest.
To disable this update check for the Guest Additions of a given virtual machine, set the value
of its /VirtualBox/GuestAdd/CheckHostVersion guest property to 0; see chapter 4.6, Guest
properties, page 75 for details.

4.2 Installing and Maintaining Guest Additions
Guest Additions are available for virtual machines running Windows, Linux, Solaris or OS/2.
The following sections describe the specifics of each variant in detail.

4.2.1 Guest Additions for Windows
The VirtualBox Windows Guest Additions are designed to be installed in a virtual machine running a Windows operating system. The following versions of Windows guests are supported:
• Microsoft Windows NT 4.0 (any service pack)
• Microsoft Windows 2000 (any service pack)

4 Guest Additions
• Microsoft Windows XP (any service pack)
• Microsoft Windows Server 2003 (any service pack)
• Microsoft Windows Server 2008
• Microsoft Windows Vista (all editions)
• Microsoft Windows 7 (all editions)
• Microsoft Windows 8 (all editions)
• Microsoft Windows Server 2012
4.2.1.1 Installation
In the “Devices” menu in the virtual machine’s menu bar, VirtualBox has a handy menu item
named “Insert Guest Additions CD image”, which mounts the Guest Additions ISO file inside
your virtual machine. A Windows guest should then automatically start the Guest Additions
installer, which installs the Guest Additions into your Windows guest. Other guest operating
systems (or if automatic start of software on CD is disabled) need manual start of the installer.
Note: For the basic Direct3D acceleration to work in a Windows Guest, you have to
install the Guest Additions in “Safe Mode”. This does not apply to the experimental
WDDM Direct3D video driver available for Vista and Windows 7 guests, see chapter
14, Known limitations, page 229 for details.a
a The

experimental WDDM driver was added with VirtualBox 4.1.

If you prefer to mount the additions manually, you can perform the following steps:
1. Start the virtual machine in which you have installed Windows.
2. Select “Mount CD/DVD-ROM” from the “Devices” menu in the virtual machine’s menu bar
and then “CD/DVD-ROM image”. This brings up the Virtual Media Manager described in
chapter 5.3, The Virtual Media Manager, page 83.
3. In the Virtual Media Manager, press the “Add” button and browse your host file system for
the VBoxGuestAdditions.iso file:
• On a Windows host, you can find this file in the VirtualBox installation directory
(usually under C:\Program files\Oracle\VirtualBox ).
• On Mac OS X hosts, you can find this file in the application bundle of VirtualBox.
(Right click on the VirtualBox icon in Finder and choose Show Package Contents. There
it is located in the Contents/MacOS folder.)
• On a Linux host, you can find this file in the additions folder under where you
installed VirtualBox (normally /opt/VirtualBox/).
• On Solaris hosts, you can find this file in the additions folder under where you
installed VirtualBox (normally /opt/VirtualBox).
4. Back in the Virtual Media Manager, select that ISO file and press the “Select” button. This
will mount the ISO file and present it to your Windows guest as a CD-ROM.

4 Guest Additions
Unless you have the Autostart feature disabled in your Windows guest, Windows will now
autostart the VirtualBox Guest Additions installation program from the Additions ISO. If the
Autostart feature has been turned off, choose VBoxWindowsAdditions.exe from the CD/DVD
drive inside the guest to start the installer.
The installer will add several device drivers to the Windows driver database and then invoke
the hardware detection wizard.
Depending on your configuration, it might display warnings that the drivers are not digitally
signed. You must confirm these in order to continue the installation and properly install the
Additions.
After installation, reboot your guest operating system to activate the Additions.
4.2.1.2 Updating the Windows Guest Additions
Windows Guest Additions can be updated by running the installation program again, as previously described. This will then replace the previous Additions drivers with updated versions.
Alternatively, you may also open the Windows Device Manager and select “Update driver...“
for two devices:
1. the VirtualBox Graphics Adapter and
2. the VirtualBox System Device.
For each, choose to provide your own driver and use “Have Disk” to point the wizard to the
CD-ROM drive with the Guest Additions.
4.2.1.3 Unattended Installation
As a prerequiste for performing an unattended installation of the VirtualBox Guest Additions on
a Windows guest, there need to be Oracle CA (Certificate Authority) certificates installed in order
to prevent user intervention popus which will undermine a silent installation.
Note: On some Windows versions like Windows 2000 and Windows XP the user intervention popups mentioned above always will be displayed, even after importing the
Oracle certificates.
Since VirtualBox 4.2 installing those CA certificates on a Windows guest can be done in an
automated fashion using the VBoxCertUtil.exe utility found on the Guest Additions installation
CD in the cert folder:
• Log in as Administrator on the guest.
• Mount the VirtualBox Guest Additions .ISO.
• Open a command line window on the guest and change to the cert folder on the VirtualBox
Guest Additions CD.
• Do
VBoxCertUtil add-trusted-publisher oracle-vbox.cer --root oracle-vbox.cer

This will install the certificates to the certificate store. When installing the same certificate
more than once, an appropriate error will be displayed.
Prior to VirtualBox 4.2 the Oracle CA certificates need to be imported in more manual style
using the certutil.exe utility, which is shipped since Windows Vista. For Windows versions
before Vista you need to download and install certutil.exe manually. Since the certificates
are not accompanied on the VirtualBox Guest Additions CD-ROM prior to 4.2, these need to get
extracted from a signed VirtualBox executable first.
In the following example the needed certificates will be extracted from the VirtualBox Windows Guest Additions installer on the CD-ROM:

4 Guest Additions
VeriSign Code Signing CA
• In the Windows Explorer, right click on VBoxWindowsAdditions-.exe, click
on “Properties”
• Go to tab “Digital Signatures”, choose “Oracle Corporation” and click on “Details”
• In tab “General” click on “View Certificate”
• In tab “Certification Path” select “VeriSign Class 3 Public Primary CA”
• Click on “View Certificate”
• In tab “Details” click on “Copy to File ...“
• In the upcoming wizard choose “DER encoded binary X.509 (.CER)“ and save the certificate
file to a local path, finish the wizard
• Close certificate dialog for “Verisign Class 3 Code Signing 2010 CA”
Oracle Corporation
• In the Windows Explorer, right click on VBoxWindowsAdditions-.exe, click
on “Properties”
• Go to tab “Digital Signatures”, choose “Oracle Corporation” and click on “Details”
• In tab “General” click on “View Certificate”
• In tab “Details” click on “Copy to File ...“
• In the upcoming wizard choose “DER encoded binary X.509 (.CER)“ and save the certificate
file to a local path, finish the wizard
• Close certificate dialog for “Oracle Corporation”
After exporting the two certificates above they can be imported into the certificate store using
the certutil.exe utility:
certutil -addstore -f Root ""

In order to allow for completely unattended guest installations, you can specify a command
line parameter to the install launcher:
VBoxWindowsAdditions.exe /S

This automatically installs the right files and drivers for the corresponding platform (32- or
64-bit).
Note: By default on an unattended installation on a Windows 7 or 8 guest, there will
be the XPDM graphics driver installed. This graphics driver does not support Windows Aero / Direct3D on the guest - instead the experimental WDDM graphics driver
needs to be installed. To select this driver by default, add the command line parameter
/with_wddm when invoking the Windows Guest Additions installer.

Note: For Windows Aero to run correctly on a guest, the guest’s VRAM size needs to
be configured to at least 128 MB.
For more options regarding unattended guest installations, consult the command line help by
using the command:
VBoxWindowsAdditions.exe /?

4 Guest Additions
4.2.1.4 Manual file extraction
If you would like to install the files and drivers manually, you can extract the files from the
Windows Guest Additions setup by typing:
VBoxWindowsAdditions.exe /extract

To explicitly extract the Windows Guest Additions for another platform than the current running one (e.g. 64-bit files on a 32-bit system), you have to execute the appropriate platform
installer (VBoxWindowsAdditions-x86.exe or VBoxWindowsAdditions-amd64.exe) with the
/extract parameter.

4.2.2 Guest Additions for Linux
Like the Windows Guest Additions, the VirtualBox Guest Additions for Linux are a set of device
drivers and system applications which may be installed in the guest operating system.
The following Linux distributions are officially supported:
• Oracle Linux as of version 5 including UEK kernels;
• Fedora as of Fedora Core 4;
• Redhat Enterprise Linux as of version 3;
• SUSE and openSUSE Linux as of version 9;
• Ubuntu as of version 5.10.
Many other distributions are known to work with the Guest Additions.
The version of the Linux kernel supplied by default in SUSE and openSUSE 10.2, Ubuntu 6.10
(all versions) and Ubuntu 6.06 (server edition) contains a bug which can cause it to crash during
startup when it is run in a virtual machine. The Guest Additions work in those distributions.
Note that some Linux distributions already come with all or part of the VirtualBox Guest
Additions. You may choose to keep the distribution’s version of the Guest Additions but these
are often not up to date and limited in functionality, so we recommend replacing them with the
Guest Additions that come with VirtualBox. The VirtualBox Linux Guest Additions installer tries
to detect existing installation and replace them but depending on how the distribution integrates
the Guest Additions, this may require some manual interaction. It is highly recommended to
take a snapshot of the virtual machine before replacing pre-installed Guest Additions.
4.2.2.1 Installing the Linux Guest Additions
The VirtualBox Guest Additions for Linux are provided on the same virtual CD-ROM file as the
Guest Additions for Windows described above. They also come with an installation program
guiding you through the setup process, although, due to the significant differences between
Linux distributions, installation may be slightly more complex.
Installation generally involves the following steps:
1. Before installing the Guest Additions, you will have to prepare your guest system for
building external kernel modules. This works similarly as described in chapter 2.3.2, The
VirtualBox kernel module, page 38, except that this step must now be performed in your
Linux guest instead of on a Linux host system, as described there.
Again, as with Linux hosts, we recommend using DKMS if it is available for the guest
system. If it is not installed, use this command for Ubuntu/Debian systems:
sudo apt-get install dkms

or for Fedora systems:

4 Guest Additions
yum install dkms

Be sure to install DKMS before installing the Linux Guest Additions. If DKMS is not available
or not installed, the guest kernel modules will need to be recreated manually whenever the
guest kernel is updated using the command
/etc/init.d/vboxadd setup

as root.
2. Insert the VBoxGuestAdditions.iso CD file into your Linux guest’s virtual CD-ROM drive,
exactly the same way as described for a Windows guest in chapter 4.2.1.1, Installation, page
62.
3. Change to the directory where your CD-ROM drive is mounted and execute as root:
sh ./VBoxLinuxAdditions.run

For your convenience, we provide the following step-by-step instructions for freshly installed
copies of recent versions of the most popular Linux distributions. After these preparational steps,
you can execute the VirtualBox Guest Additions installer as described above.
Ubuntu
1. In order to fully update your guest system, open a terminal and run
apt-get update

as root followed by
apt-get upgrade

2. Install DKMS using
apt-get install dkms

3. Reboot your guest system in order to activate the updates and then proceed as described
above.
Fedora
1. In order to fully update your guest system, open a terminal and run
yum update

as root.
2. Install DKMS and the GNU C compiler using
yum install dkms

followed by
yum install gcc

3. Reboot your guest system in order to activate the updates and then proceed as described
above.

4 Guest Additions
openSUSE
1. In order to fully update your guest system, open a terminal and run
zypper update

as root.
2. Install the make tool and the GNU C compiler using
zypper install make gcc

3. Reboot your guest system in order to activate the updates.
4. Find out which kernel you are running using
uname -a

An example would be 2.6.31.12-0.2-default which refers to the “default” kernel. Then
install the correct kernel development package. In the above example this would be
zypper install kernel-default-devel

5. Make sure that your running kernel (uname -a) and the kernel packages you have installed
(rpm -qa kernel\*) have the exact same version number. Proceed with the installation
as described above.
SuSE Linux Enterprise Desktop (SLED)
1. In order to fully update your guest system, open a terminal and run
zypper update

as root.
2. Install the GNU C compiler using
zypper install gcc

3. Reboot your guest system in order to activate the updates.
4. Find out which kernel you are running using
uname -a

An example would be 2.6.27.19-5.1-default which refers to the “default” kernel. Then
install the correct kernel development package. In the above example this would be
zypper install kernel-syms kernel-source

5. Make sure that your running kernel (uname -a) and the kernel packages you have installed
(rpm -qa kernel\*) have the exact same version number. Proceed with the installation
as described above.
Mandrake
1. Mandrake ships with the VirtualBox Guest Additions which will be replaced if you follow
these steps.
2. In order to fully update your guest system, open a terminal and run
urpmi --auto-update

as root.
3. Reboot your system in order to activate the updates.
4. Install DKMS using
urpmi dkms

and make sure to choose the correct kernel-devel package when asked by the installer (use
uname -a to compare).

4 Guest Additions
Oracle Linux, Red Hat Enterprise Linux and CentOS
1. For versions prior to 6, add divider=10 to the kernel boot options in /etc/grub.conf to
reduce the idle CPU load.
2. In order to fully update your guest system, open a terminal and run
yum update

as root.
3. Install the GNU C compiler and the kernel development packages using
yum install gcc

followed by
yum install kernel-devel

For Oracle UEK kernels, use
yum install kernel-uek-devel

to install the UEK kernel headers.
4. Reboot your guest system in order to activate the updates and then proceed as described
above.
5. In case Oracle Linux does not find the required packages, you either have to install them
from a different source (e.g. DVD) or use Oracle’s public Yum server located at http:
//public-yum.oracle.com.
Debian
1. In order to fully update your guest system, open a terminal and run
apt-get update

as root followed by
apt-get upgrade

2. Install the make tool and the GNU C compiler using
apt-get install make gcc

3. Reboot your guest system in order to activate the updates.
4. Determine the exact version of your kernel using uname -a and install the correct version
of the linux-headers package, e.g. using
apt-get install linux-headers-2.6.26-2-686

4.2.2.2 Graphics and mouse integration
In Linux and Solaris guests, VirtualBox graphics and mouse integration goes through the X Window System. VirtualBox can use the X.Org variant of the system (or XFree86 version 4.3 which
is identical to the first X.Org release). During the installation process, the X.Org display server
will be set up to use the graphics and mouse drivers which come with the Guest Additions.
After installing the Guest Additions into a fresh installation of a supported Linux distribution
or Solaris system (many unsupported systems will work correctly too), the guest’s graphics mode
will change to fit the size of the VirtualBox window on the host when it is resized. You can also
ask the guest system to switch to a particular resolution by sending a “video mode hint” using
the VBoxManage tool.

4 Guest Additions
Multiple guest monitors are supported in guests using the X.Org server version 1.3 (which is
part of release 7.3 of the X Window System version 11) or a later version. The layout of the guest
screens can be adjusted as needed using the tools which come with the guest operating system.
If you want to understand more about the details of how the X.Org drivers are set up (in
particular if you wish to use them in a setting which our installer doesn’t handle correctly), you
should read chapter 9.4.2, Guest graphics and mouse driver setup in depth, page 165.
4.2.2.3 Updating the Linux Guest Additions
The Guest Additions can simply be updated by going through the installation procedure again
with an updated CD-ROM image. This will replace the drivers with updated versions. You should
reboot after updating the Guest Additions.
4.2.2.4 Uninstalling the Linux Guest Additions
If you have a version of the Guest Additions installed on your virtual machine and wish to
remove it without installing new ones, you can do so by inserting the Guest Additions CD image
into the virtual CD-ROM drive as described above and running the installer for the current Guest
Additions with the “uninstall” parameter from the path that the CD image is mounted on in the
guest:
sh ./VBoxLinuxAdditions.run uninstall

While this will normally work without issues, you may need to do some manual cleanup of
the guest (particularly of the XFree86Config or xorg.conf file) in some cases, particularly if the
Additions version installed or the guest operating system were very old, or if you made your own
changes to the Guest Additions setup after you installed them.
Starting with version 3.1.0, you can uninstall the Additions by invoking
/opt/VBoxGuestAdditions-4.3.18/uninstall.sh

Please replace /opt/VBoxGuestAdditions-4.3.18 with the correct Guest Additions installation
directory.

4.2.3 Guest Additions for Solaris
Like the Windows Guest Additions, the VirtualBox Guest Additions for Solaris take the form of
a set of device drivers and system applications which may be installed in the guest operating
system.
The following Solaris distributions are officially supported:
• Solaris 11 including Solaris 11 Express;
• Solaris 10 (u5 and higher);
Other distributions may work if they are based on comparable software releases.
4.2.3.1 Installing the Solaris Guest Additions
The VirtualBox Guest Additions for Solaris are provided on the same ISO CD-ROM as the Additions for Windows and Linux described above. They also come with an installation program
guiding you through the setup process.
Installation involves the following steps:

4 Guest Additions
1. Mount the VBoxGuestAdditions.iso file as your Solaris guest’s virtual CD-ROM drive,
exactly the same way as described for a Windows guest in chapter 4.2.1.1, Installation,
page 62.
If in case the CD-ROM drive on the guest doesn’t get mounted (observed on some versions
of Solaris 10), execute as root:
svcadm restart volfs

2. Change to the directory where your CD-ROM drive is mounted and execute as root:
pkgadd -G -d ./VBoxSolarisAdditions.pkg

3. Choose “1” and confirm installation of the Guest Additions package. After the installation
is complete, re-login to X server on your guest to activate the X11 Guest Additions.
4.2.3.2 Uninstalling the Solaris Guest Additions
The Solaris Guest Additions can be safely removed by removing the package from the guest.
Open a root terminal session and execute:
pkgrm SUNWvboxguest

4.2.3.3 Updating the Solaris Guest Additions
The Guest Additions should be updated by first uninstalling the existing Guest Additions and
then installing the new ones. Attempting to install new Guest Additions without removing the
existing ones is not possible.

4.2.4 Guest Additions for OS/2
VirtualBox also ships with a set of drivers that improve running OS/2 in a virtual machine. Due
to restrictions of OS/2 itself, this variant of the Guest Additions has a limited feature set; see
chapter 14, Known limitations, page 229 for details.
The OS/2 Guest Additions are provided on the same ISO CD-ROM as those for the other
platforms. As a result, mount the ISO in OS/2 as described previously. The OS/2 Guest Additions
are located in the directory \32bit\OS2.
As we do not provide an automatic installer at this time, please refer to the readme.txt file in
that directory, which describes how to install the OS/2 Guest Additions manually.

4.3 Shared folders
With the “shared folders” feature of VirtualBox, you can access files of your host system from
within the guest system. This is similar how you would use network shares in Windows networks
– except that shared folders do not need require networking, only the Guest Additions. Shared
Folders are supported with Windows (2000 or newer), Linux and Solaris guests.
Shared folders must physically reside on the host and are then shared with the guest, which
uses a special file system driver in the Guest Addition to talk to the host. For Windows guests,
shared folders are implemented as a pseudo-network redirector; for Linux and Solaris guests,
the Guest Additions provide a virtual file system.
To share a host folder with a virtual machine in VirtualBox, you must specify the path of that
folder and choose for it a “share name” that the guest can use to access it. Hence, first create the
shared folder on the host; then, within the guest, connect to it.
There are several ways in which shared folders can be set up for a particular virtual machine:
• In the window of a running VM, you can select “Shared folders” from the “Devices” menu,
or click on the folder icon on the status bar in the bottom right corner.

4 Guest Additions
• If a VM is not currently running, you can configure shared folders in each virtual machine’s
“Settings” dialog.
• From the command line, you can create shared folders using VBoxManage, as follows:
VBoxManage sharedfolder add "VM name" --name "sharename" --hostpath "C:\test"

See chapter 8.29, VBoxManage sharedfolder add/remove, page 145 for details.
There are two types of shares:
1. VM shares which are only available to the VM for which they have been defined;
2. transient VM shares, which can be added and removed at runtime and do not persist after
a VM has stopped; for these, add the --transient option to the above command line.
Shared folders have read/write access to the files at the host path by default. To restrict the
guest to have read-only access, create a read-only shared folder. This can either be achieved
using the GUI or by appending the parameter --readonly when creating the shared folder with
VBoxManage.
Starting with version 4.0, VirtualBox shared folders also support symbolic links (symlinks),
under the following conditions:
1. The host operating system must support symlinks (i.e. a Mac, Linux or Solaris host is
required).
2. Currently only Linux and Solaris Guest Additions support symlinks.

4.3.1 Manual mounting
You can mount the shared folder from inside a VM the same way as you would mount an ordinary
network share:
• In a Windows guest, shared folders are browseable and therefore visible in Windows Explorer. So, to attach the host’s shared folder to your Windows guest, open Windows Explorer and look for it under “My Networking Places” -> “Entire Network” -> “VirtualBox
Shared Folders”. By right-clicking on a shared folder and selecting “Map network drive”
from the menu that pops up, you can assign a drive letter to that shared folder.
Alternatively, on the Windows command line, use the following:
net use x: \\vboxsvr\sharename

While vboxsvr is a fixed name (note that vboxsrv would also work), replace “x:“ with
the drive letter that you want to use for the share, and sharename with the share name
specified with VBoxManage.
• In a Linux guest, use the following command:
mount -t vboxsf [-o OPTIONS] sharename mountpoint

To mount a shared folder during boot, add the following entry to /etc/fstab:
sharename

mountpoint

vboxsf

defaults

• In a Solaris guest, use the following command:
mount -F vboxfs [-o OPTIONS] sharename mountpoint

Replace sharename (use lowercase) with the share name specified with VBoxManage or the
GUI, and mountpoint with the path where you want the share to be mounted on the guest
(e.g. /mnt/share). The usual mount rules apply, that is, create this directory first if it does
not exist yet.
Here is an example of mounting the shared folder for the user “jack” on Solaris:

4 Guest Additions
$ id
uid=5000(jack) gid=1(other)
$ mkdir /export/home/jack/mount
$ pfexec mount -F vboxfs -o uid=5000,gid=1 jackshare /export/home/jack/mount
$ cd ~/mount
$ ls
sharedfile1.mp3 sharedfile2.txt
$

Beyond the standard options supplied by the mount command, the following are available:
iocharset CHARSET

to set the character set used for I/O operations. Note that on Linux guests, if the “iocharset”
option is not specified then the Guest Additions driver will attempt to use the character set
specified by the CONFIG_NLS_DEFAULT kernel option. If this option is not set either then
UTF-8 will be used. Also,
convertcp CHARSET

is available in order to specify the character set used for the shared folder name (utf8 by
default).
The generic mount options (documented in the mount manual page) apply also. Especially useful are the options uid, gid and mode, as they allow access by normal users (in
read/write mode, depending on the settings) even if root has mounted the filesystem.

4.3.2 Automatic mounting
Starting with version 4.0, VirtualBox can mount shared folders automatically, at your option. If
automatic mounting is enabled for a specific shared folder, the Guest Additions will automatically
mount that folder as soon as a user logs into the guest OS. The details depend on the guest OS
type:
• With Windows guests, any auto-mounted shared folder will receive its own drive letter
(e.g. E:) depending on the free drive letters remaining in the guest.
If there no free drive letters left, auto-mounting will fail; as a result, the number of automounted shared folders is typically limited to 22 or less with Windows guests.
• With Linux guests, auto-mounted shared folders are mounted into the /media directory,
along with the prefix sf_. For example, the shared folder myfiles would be mounted to
/media/sf_myfiles on Linux and /mnt/sf_myfiles on Solaris.
The guest property /VirtualBox/GuestAdd/SharedFolders/MountPrefix determines
the prefix that is used. Change that guest property to a value other than “sf” to change
that prefix; see chapter 4.6, Guest properties, page 75 for details.
Note: Access to auto-mounted shared folders is only granted to the user group vboxsf,
which is created by the VirtualBox Guest Additions installer. Hence guest users have to
be member of that group to have read/write access or to have read-only access in case
the folder is not mapped writable.
To change the mount directory to something other than /media, you can set the guest
property /VirtualBox/GuestAdd/SharedFolders/MountDir.
• Solaris guests behave like Linux guests except that /mnt is used as the default mount
directory instead of /media.
To have any changes to auto-mounted shared folders applied while a VM is running, the guest
OS needs to be rebooted. (This applies only to auto-mounted shared folders, not the ones which
are mounted manually.)

4 Guest Additions

4.4 Hardware-accelerated graphics
4.4.1 Hardware 3D acceleration (OpenGL and Direct3D 8/9)
The VirtualBox Guest Additions contain experimental hardware 3D support for Windows, Linux
and Solaris guests.1
With this feature, if an application inside your virtual machine uses 3D features through the
OpenGL or Direct3D 8/9 programming interfaces, instead of emulating them in software (which
would be slow), VirtualBox will attempt to use your host’s 3D hardware. This works for all
supported host platforms (Windows, Mac, Linux, Solaris), provided that your host operating
system can make use of your accelerated 3D hardware in the first place.
The 3D acceleration currently has the following preconditions:
1. It is only available for certain Windows, Linux and Solaris guests. In particular:
• 3D acceleration with Windows guests requires Windows 2000, Windows XP, Vista or
Windows 7. Both OpenGL and Direct3D 8/9 (not with Windows 2000) are supported
(experimental).
• OpenGL on Linux requires kernel 2.6.27 and higher as well as X.org server version 1.5
and higher. Ubuntu 10.10 and Fedora 14 have been tested and confirmed as working.
• OpenGL on Solaris guests requires X.org server version 1.5 and higher.
2. The Guest Additions must be installed.
Note: For the basic Direct3D acceleration to work in a Windows Guest, VirtualBox
needs to replace Windows system files in the virtual machine. As a result, the Guest
Additions installation program offers Direct3D acceleration as an option that must be
explicitly enabled. Also, you must install the Guest Additions in “Safe Mode”. This
does not apply to the experimental WDDM Direct3D video driver available for Vista
and Windows 7 guests, see chapter 14, Known limitations, page 229 for details.
3. Because 3D support is still experimental at this time, it is disabled by default and must be
manually enabled in the VM settings (see chapter 3.3, General settings, page 48).
Note: Untrusted guest systems should not be allowed to use VirtualBox’s 3D acceleration features, just as untrusted host software should not be allowed to use 3D acceleration. Drivers for 3D hardware are generally too complex to be made properly secure
and any software which is allowed to access them may be able to compromise the operating system running them. In addition, enabling 3D acceleration gives the guest direct
access to a large body of additional program code in the VirtualBox host process which
it might conceivably be able to use to crash the virtual machine.

With VirtualBox 4.1, Windows Aero theme support is added for Windows Vista and Windows 7
guests. To enable Aero theme support, the experimental VirtualBox WDDM video driver must be
installed, which is available with the Guest Additions installation. Since the WDDM video driver
is still experimental at this time, it is not installed by default and must be manually selected in
the Guest Additions installer by answering “No” int the “Would you like to install basic Direct3D
support” dialog displayed when the Direct3D feature is selected.
1 OpenGL

support for Windows guests was added with VirtualBox 2.1; support for Linux and Solaris followed with
VirtualBox 2.2. With VirtualBox 3.0, Direct3D 8/9 support was added for Windows guests. OpenGL 2.0 is now
supported as well. With VirtualBox 4.1 Windows Aero theme support is added for Windows Vista and Windows 7
guests (experimental)

4 Guest Additions
Note: Unlike the current basic Direct3D support, the WDDM video driver installation
does not require the “Safe Mode”.
The Aero theme is not enabled by default. To enable it
• In Windows Vista guest: right-click on the desktop, in the context menu select “Personalize”, then select “Windows Color and Appearance” in the “Personalization” window, in the
“Appearance Settings” dialog select “Windows Aero” and press “OK”
• In Windows 7 guest: right-click on the desktop, in the context menu select “Personalize”
and select any Aero theme in the “Personalization” window
Technically, VirtualBox implements this by installing an additional hardware 3D driver inside
your guest when the Guest Additions are installed. This driver acts as a hardware 3D driver
and reports to the guest operating system that the (virtual) hardware is capable of 3D hardware
acceleration. When an application in the guest then requests hardware acceleration through
the OpenGL or Direct3D programming interfaces, these are sent to the host through a special
communication tunnel implemented by VirtualBox, and then the host performs the requested 3D
operation via the host’s programming interfaces.

4.4.2 Hardware 2D video acceleration for Windows guests
Starting with version 3.1, the VirtualBox Guest Additions contain experimental hardware 2D
video acceleration support for Windows guests.
With this feature, if an application (e.g. a video player) inside your Windows VM uses 2D
video overlays to play a movie clip, then VirtualBox will attempt to use your host’s video acceleration hardware instead of performing overlay stretching and color conversion in software (which
would be slow). This currently works for Windows, Linux and Mac host platforms, provided that
your host operating system can make use of 2D video acceleration in the first place.
The 2D video acceleration currently has the following preconditions:
1. It is only available for Windows guests (XP or later).
2. The Guest Additions must be installed.
3. Because 2D support is still experimental at this time, it is disabled by default and must be
manually enabled in the VM settings (see chapter 3.3, General settings, page 48).
Technically, VirtualBox implements this by exposing video overlay DirectDraw capabilities in
the Guest Additions video driver. The driver sends all overlay commands to the host through
a special communication tunnel implemented by VirtualBox. On the host side, OpenGL is then
used to implement color space transformation and scaling

4.5 Seamless windows
With the “seamless windows” feature of VirtualBox, you can have the windows that are displayed
within a virtual machine appear side by side next to the windows of your host. This feature
is supported for the following guest operating systems (provided that the Guest Additions are
installed):
• Windows guests (support added with VirtualBox 1.5);
• Supported Linux or Solaris guests running the X Window System (added with VirtualBox
1.6).

4 Guest Additions
After seamless windows are enabled (see below), VirtualBox suppresses the display of the
Desktop background of your guest, allowing you to run the windows of your guest operating
system seamlessly next to the windows of your host:

To enable seamless mode, after starting the virtual machine, press the Host key (normally the
right control key) together with “L”. This will enlarge the size of the VM’s display to the size
of your host screen and mask out the guest operating system’s background. To go back to the
“normal” VM display (i.e. to disable seamless windows), press the Host key and “L” again.

4.6 Guest properties
Starting with version 2.1, VirtualBox allows for requesting certain properties from a running
guest, provided that the VirtualBox Guest Additions are installed and the VM is running. This is
good for two things:
1. A number of predefined VM characteristics are automatically maintained by VirtualBox and
can be retrieved on the host, e.g. to monitor VM performance and statistics.
2. In addition, arbitrary string data can be exchanged between guest and host. This works in
both directions.
To accomplish this, VirtualBox establishes a private communication channel between the
VirtualBox Guest Additions and the host, and software on both sides can use this channel to
exchange string data for arbitrary purposes. Guest properties are simply string keys to which a
value is attached. They can be set (written to) by either the host and the guest, and they can
also be read from both sides.
In addition to establishing the general mechanism of reading and writing values, a set of
predefined guest properties is automatically maintained by the VirtualBox Guest Additions to
allow for retrieving interesting guest data such as the guest’s exact operating system and service
pack level, the installed version of the Guest Additions, users that are currently logged into
the guest OS, network statistics and more. These predefined properties are all prefixed with
/VirtualBox/ and organized into a hierarchical tree of keys.

4 Guest Additions
Some of this runtime information is shown when you select “Session Information Dialog” from
a virtual machine’s “Machine” menu.
A more flexible way to use this channel is via the VBoxManage guestproperty command set;
see chapter 8.30, VBoxManage guestproperty, page 145 for details. For example, to have all the
available guest properties for a given running VM listed with their respective values, use this:
$ VBoxManage guestproperty enumerate "Windows Vista III"
VirtualBox Command Line Management Interface Version 4.3.18
(C) 2005-2014 Oracle Corporation
All rights reserved.
Name: /VirtualBox/GuestInfo/OS/Product, value: Windows Vista Business Edition,
timestamp: 1229098278843087000, flags:
Name: /VirtualBox/GuestInfo/OS/Release, value: 6.0.6001,
timestamp: 1229098278950553000, flags:
Name: /VirtualBox/GuestInfo/OS/ServicePack, value: 1,
timestamp: 1229098279122627000, flags:
Name: /VirtualBox/GuestAdd/InstallDir,
value: C:/Program Files/Oracle/VirtualBox
Guest Additions, timestamp: 1229098279269739000, flags:
Name: /VirtualBox/GuestAdd/Revision, value: 40720,
timestamp: 1229098279345664000, flags:
Name: /VirtualBox/GuestAdd/Version, value: 4.3.18,
timestamp: 1229098279479515000, flags:
Name: /VirtualBox/GuestAdd/Components/VBoxControl.exe, value: 4.3.18r40720,
timestamp: 1229098279651731000, flags:
Name: /VirtualBox/GuestAdd/Components/VBoxHook.dll, value: 4.3.18r40720,
timestamp: 1229098279804835000, flags:
Name: /VirtualBox/GuestAdd/Components/VBoxDisp.dll, value: 4.3.18r40720,
timestamp: 1229098279880611000, flags:
Name: /VirtualBox/GuestAdd/Components/VBoxMRXNP.dll, value: 4.3.18r40720,
timestamp: 1229098279882618000, flags:
Name: /VirtualBox/GuestAdd/Components/VBoxService.exe, value: 4.3.18r40720,
timestamp: 1229098279883195000, flags:
Name: /VirtualBox/GuestAdd/Components/VBoxTray.exe, value: 4.3.18r40720,
timestamp: 1229098279885027000, flags:
Name: /VirtualBox/GuestAdd/Components/VBoxGuest.sys, value: 4.3.18r40720,
timestamp: 1229098279886838000, flags:
Name: /VirtualBox/GuestAdd/Components/VBoxMouse.sys, value: 4.3.18r40720,
timestamp: 1229098279890600000, flags:
Name: /VirtualBox/GuestAdd/Components/VBoxSF.sys, value: 4.3.18r40720,
timestamp: 1229098279893056000, flags:
Name: /VirtualBox/GuestAdd/Components/VBoxVideo.sys, value: 4.3.18r40720,
timestamp: 1229098279895767000, flags:
Name: /VirtualBox/GuestInfo/OS/LoggedInUsers, value: 1,
timestamp: 1229099826317660000, flags:
Name: /VirtualBox/GuestInfo/OS/NoLoggedInUsers, value: false,
timestamp: 1229098455580553000, flags:
Name: /VirtualBox/GuestInfo/Net/Count, value: 1,
timestamp: 1229099826299785000, flags:
Name: /VirtualBox/HostInfo/GUI/LanguageID, value: C,
timestamp: 1229098151272771000, flags:
Name: /VirtualBox/GuestInfo/Net/0/V4/IP, value: 192.168.2.102,
timestamp: 1229099826300088000, flags:
Name: /VirtualBox/GuestInfo/Net/0/V4/Broadcast, value: 255.255.255.255,
timestamp: 1229099826300220000, flags:
Name: /VirtualBox/GuestInfo/Net/0/V4/Netmask, value: 255.255.255.0,
timestamp: 1229099826300350000, flags:
Name: /VirtualBox/GuestInfo/Net/0/Status, value: Up,
timestamp: 1229099826300524000, flags:
Name: /VirtualBox/GuestInfo/OS/LoggedInUsersList, value: username,
timestamp: 1229099826317386000, flags:

To query the value of a single property, use the “get” subcommand like this:
$ VBoxManage guestproperty get "Windows Vista III" "/VirtualBox/GuestInfo/OS/Product"
VirtualBox Command Line Management Interface Version 4.3.18

4 Guest Additions
(C) 2005-2014 Oracle Corporation
All rights reserved.
Value: Windows Vista Business Edition

To add or change guest properties from the guest, use the tool VBoxControl. This tool is
included in the Guest Additions of VirtualBox 2.2 or later. When started from a Linux guest, this
tool requires root privileges for security reasons:
$ sudo VBoxControl guestproperty enumerate
VirtualBox Guest Additions Command Line Management Interface Version 4.3.18
(C) 2009-2014 Oracle Corporation
All rights reserved.
Name: /VirtualBox/GuestInfo/OS/Release, value: 2.6.28-18-generic,
timestamp: 1265813265835667000, flags:
Name: /VirtualBox/GuestInfo/OS/Version, value: #59-Ubuntu SMP Thu Jan 28 01:23:03 UTC 2010,
timestamp: 1265813265836305000, flags:
...

For more complex needs, you can use the VirtualBox programming interfaces; see chapter 11,
VirtualBox programming interfaces, page 208.

4.7 Guest control
Starting with version 3.2, the Guest Additions of VirtualBox allow starting applications inside a
VM from the host system.
For this to work, the application needs to be installed inside the guest; no additional software
needs to be installed on the host. Additionally, text mode output (to stdout and stderr) can be
shown on the host for further processing along with options to specify user credentials and a
timeout value (in milliseconds) to limit time the application is able to run.
This feature can be used to automate deployment of software within the guest.
Starting with version 4.0, the Guest Additions for Windows allow for automatic updating (only
already installed Guest Additions 4.0 or later). Also, copying files from host to the guest as well
as remotely creating guest directories is available.
To use these features, use the VirtualBox command line, see chapter 8.31, VBoxManage guestcontrol, page 146.

4.8 Memory overcommitment
In server environments with many VMs; the Guest Additions can be used to share physical host
memory between several VMs, reducing the total amount of memory in use by the VMs. If
memory usage is the limiting factor and CPU resources are still available, this can help with
packing more VMs on each host.

4.8.1 Memory ballooning
Starting with version 3.2, the Guest Additions of VirtualBox can change the amount of host
memory that a VM uses while the machine is running. Because of how this is implemented, this
feature is called “memory ballooning”.
Note: VirtualBox supports memory ballooning only on 64-bit hosts, and it is not supported on Mac OS X hosts.

4 Guest Additions
Normally, to change the amount of memory allocated to a virtual machine, one has to shut
down the virtual machine entirely and modify its settings. With memory ballooning, memory
that was allocated for a virtual machine can be given to another virtual machine without having
to shut the machine down.
When memory ballooning is requested, the VirtualBox Guest Additions (which run inside the
guest) allocate physical memory from the guest operating system on the kernel level and lock
this memory down in the guest. This ensures that the guest will not use that memory any longer:
no guest applications can allocate it, and the guest kernel will not use it either. VirtualBox can
then re-use this memory and give it to another virtual machine.
The memory made available through the ballooning mechanism is only available for re-use by
VirtualBox. It is not returned as free memory to the host. Requesting balloon memory from a
running guest will therefore not increase the amount of free, unallocated memory on the host.
Effectively, memory ballooning is therefore a memory overcommitment mechanism for multiple
virtual machines while they are running. This can be useful to temporarily start another machine,
or in more complicated environments, for sophisticated memory management of many virtual
machines that may be running in parallel depending on how memory is used by the guests.
At this time, memory ballooning is only supported through VBoxManage. Use the following command to increase or decrease the size of the memory balloon within a running virtual
machine that has Guest Additions installed:
VBoxManage controlvm "VM name" guestmemoryballoon

where "VM name" is the name or UUID of the virtual machine in question and is the amount
of memory to allocate from the guest in megabytes. See chapter 8.13, VBoxManage controlvm,
page 134 for more information.
You can also set a default balloon that will automatically be requested from the VM every time
after it has started up with the following command:
VBoxManage modifyvm "VM name" --guestmemoryballoon

By default, no balloon memory is allocated. This is a VM setting, like other modifyvm settings,
and therefore can only be set while the machine is shut down; see chapter 8.8, VBoxManage
modifyvm, page 125.

4.8.2 Page Fusion
Whereas memory ballooning simply reduces the amount of RAM that is available to a VM, Page
Fusion works differently: it avoids memory duplication between several similar running VMs.
In a server environment running several similar VMs (e.g. with identical operating systems)
on the same host, lots of memory pages are identical. VirtualBox’s Page Fusion technology,
introduced with VirtualBox 3.2, is a novel technique to efficiently identify these identical memory
pages and share them between multiple VMs.
Note: VirtualBox supports Page Fusion only on 64-bit hosts, and it is not supported on
Mac OS X hosts. Page Fusion currently works only with Windows guests (2000 and
later).
The more similar the VMs on a given host are, the more efficiently Page Fusion can reduce the
amount of host memory that is in use. It therefore works best if all VMs on a host run identical
operating systems (e.g. Windows XP Service Pack 2). Instead of having a complete copy of each
operating system in each VM, Page Fusion identifies the identical memory pages in use by these
operating systems and eliminates the duplicates, sharing host memory between several machines
(“deduplication”). If a VM tries to modify a page that has been shared with other VMs, a new
page is allocated again for that VM with a copy of the shared page (“copy on write”). All this is
fully transparent to the virtual machine.

4 Guest Additions
You may be familiar with this kind of memory overcommitment from other hypervisor products, which call this feature “page sharing” or “same page merging”. However, Page Fusion differs
significantly from those other solutions, whose approaches have several drawbacks:
1. Traditional hypervisors scan all guest memory and compute checksums (hashes) for every
single memory page. Then, they look for pages with identical hashes and compare the
entire content of those pages; if two pages produce the same hash, it is very likely that the
pages are identical in content. This, of course, can take rather long, especially if the system
is not idling. As a result, the additional memory only becomes available after a significant
amount of time (this can be hours or even days!). Even worse, this kind of page sharing
algorithm generally consumes significant CPU resources and increases the virtualization
overhead by 10-20%.
Page Fusion in VirtualBox uses logic in the VirtualBox Guest Additions to quickly identify
memory cells that are most likely identical across VMs. It can therefore achieve most of the
possible savings of page sharing almost immediately and with almost no overhead.
2. Page Fusion is also much less likely to be confused by identical memory that it will eliminate
just to learn seconds later that the memory will now change and having to perform a highly
expensive and often service-disrupting reallocation.
At this time, Page Fusion can only be controlled with VBoxManage, and only while a VM is
shut down. To enable Page Fusion for a VM, use the following command:
VBoxManage modifyvm "VM name" --pagefusion on

You can observe Page Fusion operation using some metrics. RAM/VMM/Shared shows the total
amount of fused pages, whereas the per-VM metric Guest/RAM/Usage/Shared will return the
amount of fused memory for a given VM. Please refer to chapter 8.33, VBoxManage metrics, page
154 for information on how to query metrics.

5 Virtual storage
As the virtual machine will most probably expect to see a hard disk built into its virtual computer,
VirtualBox must be able to present “real” storage to the guest as a virtual hard disk. There are
presently three methods in which to achieve this:
1. Most commonly, VirtualBox will use large image files on a real hard disk and present them
to a guest as a virtual hard disk. This is described in chapter 5.2, Disk image files (VDI,
VMDK, VHD, HDD), page 82.
2. Alternatively, if you have iSCSI storage servers, you can attach such a server to VirtualBox
as well; this is described in chapter 5.10, iSCSI servers, page 91.
3. Finally, as an advanced feature, you can allow a virtual machine to access one of your host
disks directly; this advanced feature is described in chapter 9.9.1, Using a raw host hard
disk from a guest, page 171.
Each such virtual storage device (image file, iSCSI target or physical hard disk) will need to be
connected to the virtual hard disk controller that VirtualBox presents to a virtual machine. This
is explained in the next section.

5.1 Hard disk controllers: IDE, SATA (AHCI), SCSI, SAS
In a real PC, hard disks and CD/DVD drives are connected to a device called hard disk controller
which drives hard disk operation and data transfers. VirtualBox can emulate the four most
common types of hard disk controllers typically found in today’s PCs: IDE, SATA (AHCI), SCSI
and SAS.1
• IDE (ATA) controllers are a backwards compatible yet very advanced extension of the disk
controller in the IBM PC/AT (1984). Initially, this interface worked only with hard disks,
but was later extended to also support CD-ROM drives and other types of removable media.
In physical PCs, this standard uses flat ribbon parallel cables with 40 or 80 wires. Each such
cable can connect two devices to a controller, which have traditionally been called “master”
and “slave”. Typical PCs had two connectors for such cables; as a result, support for up to
four IDE devices was most common.
In VirtualBox, each virtual machine may have one IDE contoller enabled, which gives you
up to four virtual storage devices that you can attach to the machine. (By default, one of
these four – the secondary master – is preconfigured to be the machine’s virtual CD/DVD
drive, but this can be changed.2 )
So even if your guest operating system has no support for SCSI or SATA devices, it should
always be able to see an IDE controller.
You can also select which exact type of IDE controller hardware VirtualBox should present
to the virtual machine (PIIX3, PIIX4 or ICH6). This makes no difference in terms of performance, but if you import a virtual machine from another virtualization product, the
1 SATA

support was added with VirtualBox 1.6; experimental SCSI support was added with 2.1 and fully implemented
with 2.2. Generally, storage attachments were made much more flexible with VirtualBox 3.1; see below. Support for
the LSI Logic SAS controller was added with VirtualBox 3.2.
2 The assignment of the machine’s CD/DVD drive to the secondary master was fixed before VirtualBox 3.1; it is now
changeable, and the drive can be at other slots of the IDE controller, and there can be more than one such drive.

5 Virtual storage
operating system in that machine may expect a particular controller type and crash if it
isn’t found.
After you have created a new virtual machine with the “New Virtual Machine” wizard of the
graphical user interface, you will typically see one IDE controller in the machine’s “Storage”
settings where the virtual CD/DVD drive will be attached to one of the four ports of this
controller.
• Serial ATA (SATA) is a newer standard introduced in 2003. Compared to IDE, it supports
both much higher speeds and more devices per controller. Also, with physical hardware,
devices can be added and removed while the system is running. The standard interface for
SATA controllers is called Advanced Host Controller Interface (AHCI).
Like a real SATA controller, VirtualBox’s virtual SATA controller operates faster and also
consumes fewer CPU resources than the virtual IDE controller. Also, this allows you to connect up to 30 virtual hard disks to one machine instead of just three, as with the VirtualBox
IDE controller (with the DVD drive already attached).
For this reason, starting with version 3.2 and depending on the selected guest operating
system, VirtualBox uses SATA as the default for newly created virtual machines. One virtual
SATA controller is created by default, and the default disk that is created with a new VM is
attached to this controller.
Warning: The entire SATA controller and the virtual disks attached to it (including
those in IDE compatibility mode) will not be seen by operating systems that do not
have device support for AHCI. In particular, there is no support for AHCI in Windows
before Windows Vista, so Windows XP (even SP3) will not see such disks unless you
install additional drivers. It is possible to switch from IDE to SATA after installation by
installing the SATA drivers and changing the controller type in the VM settings dialog.a
a VirtualBox

recommends the Intel Matrix Storage drivers which can be downloaded from http://

downloadcenter.intel.com/Product_Filter.aspx?ProductID=2101.

To add a SATA controller to a machine for which it has not been enabled by default (either
because it was created by an earlier version of VirtualBox, or because SATA is not supported by default by the selected guest operating system), go to the “Storage” page of the
machine’s settings dialog, click on the “Add Controller” button under the “Storage Tree”
box and then select “Add SATA Controller”. After this, the additional controller will appear
as a separate PCI device in the virtual machine, and you can add virtual disks to it.
To change the IDE compatibility mode settings for the SATA controller, please see chapter
8.19, VBoxManage storagectl, page 139.
• SCSI is another established industry standard, standing for “Small Computer System Interface”. SCSI was standardized as early as 1986 as a generic interface for data transfer
between all kinds of devices, including storage devices. Today SCSI is still used for connecting hard disks and tape devices, but it has mostly been displaced in commodity hardware.
It is still in common use in high-performance workstations and servers.
Primarily for compatibility with other virtualization software, VirtualBox optionally supports LSI Logic and BusLogic SCSI controllers, to each of which up to 15 virtual hard disks
can be attached.
To enable a SCSI controller, on the “Storage” page of a virtual machine’s settings dialog,
click on the “Add Controller” button under the “Storage Tree” box and then select “Add
SCSI Controller”. After this, the additional controller will appear as a separate PCI device
in the virtual machine.

5 Virtual storage
Warning: As with the other controller types, a SCSI controller will only be seen by
operating systems with device support for it. Windows 2003 and later ships with drivers
for the LSI Logic controller, while Windows NT 4.0 and Windows 2000 ships with
drivers for the BusLogic controller. Windows XP ships with drivers for neither.

• Serial Attached SCSI (SAS) is another bus standard which uses the SCSI command set. As
opposed to SCSI, however, with physical devices, serial cables are used instead of parallel
ones, which simplifies physical device connections. In some ways, therefore, SAS is to SCSI
what SATA is to IDE: it allows for more reliable and faster connections.
To support high-end guests which require SAS controllers, VirtualBox emulates a LSI Logic
SAS controller, which can be enabled much the same way as a SCSI controller. At this time,
up to eight devices can be connected to the SAS controller.
Warning: As with SATA, the SAS controller will only be seen by operating systems with
device support for it. In particular, there is no support for SAS in Windows before
Windows Vista, so Windows XP (even SP3) will not see such disks unless you install
additional drivers.

In summary, VirtualBox gives you the following categories of virtual storage slots:
1. four slots attached to the traditional IDE controller, which are always present (one of which
typically is a virtual CD/DVD drive);
2. 30 slots attached to the SATA controller, if enabled and supported by the guest operating
system;
3. 15 slots attached to the SCSI controller, if enabled and supported by the guest operating
system;
4. eight slots attached to the SAS controller, if enabled and supported by the guest operating
system.
Given this large choice of storage controllers, you may ask yourself which one to choose. In
general, you should avoid IDE unless it is the only controller supported by your guest. Whether
you use SATA, SCSI or SAS does not make any real difference. The variety of controllers is only
supplied for VirtualBox for compatibility with existing hardware and other hypervisors.

5.2 Disk image files (VDI, VMDK, VHD, HDD)
Disk image files reside on the host system and are seen by the guest systems as hard disks of a
certain geometry. When a guest operating system reads from or writes to a hard disk, VirtualBox
redirects the request to the image file.
Like a physical disk, a virtual disk has a size (capacity), which must be specified when the
image file is created. As opposed to a physical disk however, VirtualBox allows you to expand
an image file after creation, even if it has data already; see chapter 8.23, VBoxManage modifyhd,
page 141 for details.3
VirtualBox supports four variants of disk image files:
• Normally, VirtualBox uses its own container format for guest hard disks – Virtual Disk
Image (VDI) files. In particular, this format will be used when you create a new virtual
machine with a new disk.
3 Image

resizing was added with VirtualBox 4.0.

5 Virtual storage
• VirtualBox also fully supports the popular and open VMDK container format that is used
by many other virtualization products, in particular, by VMware.4
• VirtualBox also fully supports the VHD format used by Microsoft.
• Image files of Parallels version 2 (HDD format) are also supported.5 For lack of documentation of the format, newer formats (3 and 4) are not supported. You can however convert
such image files to version 2 format using tools provided by Parallels.
Irrespective of the disk capacity and format, as briefly mentioned in chapter 1.7, Creating your
first virtual machine, page 18, there are two options of how to create a disk image: fixed-size or
dynamically allocated.
• If you create a fixed-size image, an image file will be created on your host system which
has roughly the same size as the virtual disk’s capacity. So, for a 10G disk, you will have
a 10G file. Note that the creation of a fixed-size image can take a long time depending on
the size of the image and the write performance of your hard disk.
• For more flexible storage management, use a dynamically allocated image. This will initially be very small and not occupy any space for unused virtual disk sectors, but will grow
every time a disk sector is written to for the first time, until the drive reaches the maximum
capacity chosen when the drive was created. While this format takes less space initially,
the fact that VirtualBox needs to expand the image file consumes additional computing resources, so until the disk file size has stabilized, write operations may be slower than with
fixed size disks. However, after a time the rate of growth will slow and the average penalty
for write operations will be negligible.

5.3 The Virtual Media Manager
VirtualBox keeps track of all the hard disk, CD/DVD-ROM and floppy disk images which are
in use by virtual machines. These are often referred to as “known media” and come from two
sources:
• all media currently attached to virtual machines;
• “registered” media for compatibility with VirtualBox versions older than version 4.0. For
details about how media registration has changed with version 4.0, please refer to chapter
10.1, Where VirtualBox stores its files, page 198.
The known media can be viewed and changed in the Virtual Media Manager, which you can
access from the “File” menu in the VirtualBox main window:

4 Initial

support for VMDK was added with VirtualBox 1.4; since version 2.1, VirtualBox supports VMDK fully, meaning
that you can create snapshots and use all the other advanced features described above for VDI images with VMDK
also.
5 Support was added with VirtualBox 3.1.

5 Virtual storage

The known media are conveniently grouped in three tabs for the three possible formats. These
formats are:
• Hard disk images, either in VirtualBox’s own Virtual Disk Image (VDI) format or in the
third-party formats listed in the previous chapter;
• CD/DVD images in standard ISO format;
• floppy images in standard RAW format.
As you can see in the screenshot above, for each image, the Virtual Media Manager shows you
the full path of the image file and other information, such as the virtual machine the image is
currently attached to, if any.
The Virtual Media Manager allows you to
• remove an image from the registry (and optionally delete the image file when doing so);
• “release” an image, that is, detach it from a virtual machine if it is currently attached to
one as a virtual hard disk.
Starting with version 4.0, to create new disk images, please use the “Storage” page in a virtual
machine’s settings dialog because disk images are now by default stored in each machine’s own
folder.
Hard disk image files can be copied onto other host systems and imported into virtual machines
there, although certain guest systems (notably Windows 2000 and XP) will require that the new
virtual machine be set up in a similar way to the old one.
Note: Do not simply make copies of virtual disk images. If you import such a second
copy into a virtual machine, VirtualBox will complain with an error, since VirtualBox
assigns a unique identifier (UUID) to each disk image to make sure it is only used once.
See chapter 5.6, Cloning disk images, page 88 for instructions on this matter. Also, if
you want to copy a virtual machine to another system, VirtualBox has an import/export
facility that might be better suited for your needs; see chapter 1.14, Importing and
exporting virtual machines, page 31.

5 Virtual storage

5.4 Special image write modes
For each virtual disk image supported by VirtualBox, you can determine separately how it should
be affected by write operations from a virtual machine and snapshot operations. This applies to
all of the aforementioned image formats (VDI, VMDK, VHD or HDD) and irrespective of whether
an image is fixed-size or dynamically allocated.
By default, images are in “normal” mode. To mark an existing image with one of the nonstandard modes listed below, use VBoxManage modifyhd; see chapter 8.23, VBoxManage modifyhd, page 141. Alternatively, use VBoxManage to attach the image to a VM and use the --mtype
argument; see chapter 8.18, VBoxManage storageattach, page 137.
1. With normal images (the default setting), there are no restrictions on how guests can read
from and write to the disk.
When you take a snapshot of your virtual machine as described in chapter 1.10, Snapshots,
page 27, the state of such a “normal hard disk” will be recorded together with the snapshot,
and when reverting to the snapshot, its state will be fully reset.
(Technically, strictly speaking, the image file itself is not “reset”. Instead, when a snapshot
is taken, VirtualBox “freezes” the image file and no longer writes to it. For the write operations from the VM, a second, “differencing” image file is created which receives only the
changes to the original image; see the next section for details.)
While you can attach the same “normal” image to more than one virtual machine, only one
of these virtual machines attached to the same image file can be executed simultaneously,
as otherwise there would be conflicts if several machines write to the same image file.6
2. By contrast, write-through hard disks are completely unaffected by snapshots: their state
is not saved when a snapshot is taken, and not restored when a snapshot is restored.
3. Shareable hard disks are a variant of write-through hard disks. In principle they behave
exactly the same, i.e. their state is not saved when a snapshot is taken, and not restored
when a snapshot is restored. The difference only shows if you attach such disks to several
VMs. Shareable disks may be attached to several VMs which may run concurrently. This
makes them suitable for use by cluster filesystems between VMs and similar applications
which are explicitly prepared to access a disk concurrently. Only fixed size images can be
used in this way, and dynamically allocated images are rejected.
Warning: This is an expert feature, and misuse can lead to data loss – regular filesystems are not prepared to handle simultaneous changes by several parties.
4. Next, immutable images only remember write accesses temporarily while the virtual machine is running; all changes are lost when the virtual machine is powered on the next
time. As a result, as opposed to “normal” images, the same immutable image can be used
with several virtual machines without restrictions.
Creating an immutable image makes little sense since it would be initially empty and lose
its contents with every machine restart (unless you really want to have a disk that is always
unformatted when the machine starts up). As a result, normally, you would first create a
“normal” image and then, when you deem its contents useful, later mark it immutable.
If you take a snapshot of a machine with immutable images, then on every machine powerup, those images are reset to the state of the last (current) snapshot (instead of the state
of the original immutable image).
6 This

restriction is more lenient now than it was before VirtualBox 2.2. Previously, each “normal” disk image could only
be attached to one single machine. Now it can be attached to more than one machine so long as only one of these
machines is running.

5 Virtual storage
Note: As a special exception, immutable images are not reset if they are attached to
a machine whose last snapshot was taken while the machine was running (a so-called
“online” snapshot). As a result, if the machine’s current snapshot is such an “online”
snapshot, its immutable images behave exactly like the “normal” images described previously. To re-enable the automatic resetting of such images, delete the current snapshot of the machine.
Again, technically, VirtualBox never writes to an immutable image directly at all. All write
operations from the machine will be directed to a differencing image; the next time the
VM is powered on, the differencing image is reset so that every time the VM starts, its immutable images have exactly the same content.7 The differencing image is only reset when
the machine is powered on from within VirtualBox, not when you reboot by requesting a
reboot from within the machine. This is also why immutable images behave as described
above when snapshots are also present, which use differencing images as well.
If the automatic discarding of the differencing image on VM startup does not fit your needs,
you can turn it off using the autoreset parameter of VBoxManage modifyhd; see chapter
8.23, VBoxManage modifyhd, page 141 for details.
5. An image in multiattach mode can be attached to more than one virtual machine at the
same time, even if these machines are running simultaneously. For each virtual machine to
which such an image is attached, a differencing image is created. As a result, data that is
written to such a virtual disk by one machine is not seen by the other machines to which
the image is attached; each machine creates its own write history of the multiattach image.
Technically, a “multiattach” image behaves identically to an “immutable” image except the
differencing image is not reset every time the machine starts.
6. Finally, the read-only image is used automatically for CD/DVD images, since CDs/DVDs
can never be written to.
To illustrate the differences between the various types with respect to snapshots: Assume
you have installed your guest operating system in your VM, and you have taken a snapshot.
Imagine you have accidentally infected your VM with a virus and would like to go back to the
snapshot. With a normal hard disk image, you simply restore the snapshot, and the earlier
state of your hard disk image will be restored as well (and your virus infection will be undone).
With an immutable hard disk, all it takes is to shut down and power on your VM, and the virus
infection will be discarded. With a write-through image however, you cannot easily undo the
virus infection by means of virtualization, but will have to disinfect your virtual machine like a
real computer.
Still, you might find write-through images useful if you want to preserve critical data irrespective of snapshots, and since you can attach more than one image to a VM, you may want to have
one immutable for the operating system and one write-through for your data files.

5.5 Differencing images
The previous section hinted at differencing images and how they are used with snapshots, immutable images and multiple disk attachments. For the inquisitive VirtualBox user, this section
describes in more detail how they work.
A differencing image is a special disk image that only holds the differences to another image.
A differencing image by itself is useless, it must always refer to another image. The differencing
image is then typically referred to as a “child”, which holds the differences to its “parent”.
7 This

behavior also changed with VirtualBox 2.2. Previously, the differencing images were discarded when the machine
session ended; now they are discarded every time the machine is powered on.

5 Virtual storage
When a differencing image is active, it receives all write operations from the virtual machine
instead of its parent. The differencing image only contains the sectors of the virtual hard disk
that have changed since the differencing image was created. When the machine reads a sector
from such a virtual hard disk, it looks into the differencing image first. If the sector is present,
it is returned from there; if not, VirtualBox looks into the parent. In other words, the parent
becomes “read-only”; it is never written to again, but it is read from if a sector has not changed.
Differencing images can be chained. If another differencing image is created for a virtual disk
that already has a differencing image, then it becomes a “grandchild” of the original parent.
The first differencing image then becomes read-only as well, and write operations only go to the
second-level differencing image. When reading from the virtual disk, VirtualBox needs to look
into the second differencing image first, then into the first if the sector was not found, and then
into the original image.
There can be an unlimited number of differencing images, and each image can have more than
one child. As a result, the differencing images can form a complex tree with parents, “siblings”
and children, depending on how complex your machine configuration is. Write operations always
go to the one “active” differencing image that is attached to the machine, and for read operations,
VirtualBox may need to look up all the parents in the chain until the sector in question is found.
You can look at such a tree in the Virtual Media Manager:

In all of these situations, from the point of view of the virtual machine, the virtual hard disk
behaves like any other disk. While the virtual machine is running, there is a slight run-time I/O
overhead because VirtualBox might need to look up sectors several times. This is not noticeable
however since the tables with sector information are always kept in memory and can be looked
up quickly.
Differencing images are used in the following situations:
1. Snapshots. When you create a snapshot, as explained in the previous section, VirtualBox
“freezes” the images attached to the virtual machine and creates differencing images for
each of them (to be precise: one for each image that is not in “write-through” mode). From
the point of view of the virtual machine, the virtual disks continue to operate before, but all
write operations go into the differencing images. Each time you create another snapshot,
for each hard disk attachment, another differencing image is created and attached, forming
a chain or tree.

5 Virtual storage
In the above screenshot, you see that the original disk image is now attached to a snapshot,
representing the state of the disk when the snapshot was taken.
If you now restore a snapshot – that is, if you want to go back to the exact machine state
that was stored in the snapshot –, the following happens:
a) VirtualBox copies the virtual machine settings that were copied into the snapshot
back to the virtual machine. As a result, if you have made changes to the machine
configuration since taking the snapshot, they are undone.
b) If the snapshot was taken while the machine was running, it contains a saved machine
state, and that state is restored as well; after restoring the snapshot, the machine will
then be in “Saved” state and resume execution from there when it is next started.
Otherwise the machine will be in “Powered Off” state and do a full boot.
c) For each disk image attached to the machine, the differencing image holding all the
write operations since the current snapshot was taken is thrown away, and the original
parent image is made active again. (If you restored the “root” snapshot, then this will
be the root disk image for each attachment; otherwise, some other differencing image
descended from it.) This effectively restores the old machine state.
If you later delete a snapshot in order to free disk space, for each disk attachment, one of
the differencing images becomes obsolete. In this case, the differencing image of the disk
attachment cannot simply be deleted. Instead, VirtualBox needs to look at each sector of
the differencing image and needs to copy it back into its parent; this is called “merging”
images and can be a potentially lengthy process, depending on how large the differencing
image is. It can also temporarily need a considerable amount of extra disk space, before
the differencing image obsoleted by the merge operation is deleted.
2. Immutable images. When an image is switched to “immutable” mode, a differencing image is created as well. As with snapshots, the parent image then becomes read-only, and
the differencing image receives all the write operations. Every time the virtual machine is
started, all the immutable images which are attached to it have their respective differencing image thrown away, effectively resetting the virtual machine’s virtual disk with every
restart.

5.6 Cloning disk images
You can duplicate hard disk image files on the same host to quickly produce a second virtual
machine with the same operating system setup. However, you should only make copies of virtual
disk images using the utility supplied with VirtualBox; see chapter 8.24, VBoxManage clonehd,
page 142. This is because VirtualBox assigns a unique identity number (UUID) to each disk
image, which is also stored inside the image, and VirtualBox will refuse to work with two images
that use the same number. If you do accidentally try to reimport a disk image which you copied
normally, you can make a second copy using VirtualBox’s utility and import that instead.
Note that newer Linux distributions identify the boot hard disk from the ID of the drive. The
ID VirtualBox reports for a drive is determined from the UUID of the virtual disk image. So if you
clone a disk image and try to boot the copied image the guest might not be able to determine
its own boot disk as the UUID changed. In this case you have to adapt the disk ID in your boot
loader script (for example /boot/grub/menu.lst). The disk ID looks like this:
scsi-SATA_VBOX_HARDDISK_VB5cfdb1e2-c251e503

The ID for the copied image can be determined with
hdparm -i /dev/sda

5 Virtual storage

5.7 Host I/O caching
Starting with version 3.2, VirtualBox can optionally disable the I/O caching that the host operating system would otherwise perform on disk image files.
Traditionally, VirtualBox has opened disk image files as normal files, which results in them
being cached by the host operating system like any other file. The main advantage of this is
speed: when the guest OS writes to disk and the host OS cache uses delayed writing, the write
operation can be reported as completed to the guest OS quickly while the host OS can perform the
operation asynchronously. Also, when you start a VM a second time and have enough memory
available for the OS to use for caching, large parts of the virtual disk may be in system memory,
and the VM can access the data much faster.
Note that this applies only to image files; buffering never occurred for virtual disks residing on
remote iSCSI storage, which is the more common scenario in enterprise-class setups (see chapter
5.10, iSCSI servers, page 91).
While buffering is a useful default setting for virtualizating a few machines on a desktop
computer, there are some disadvantages to this approach:
1. Delayed writing through the host OS cache is less secure. When the guest OS writes data,
it considers the data written even though it has not yet arrived on a physical disk. If for
some reason the write does not happen (power failure, host crash), the likelihood of data
loss increases.
2. Disk image files tend to be very large. Caching them can therefore quickly use up the entire
host OS cache. Depending on the efficiency of the host OS caching, this may slow down
the host immensely, especially if several VMs run at the same time. For example, on Linux
hosts, host caching may result in Linux delaying all writes until the host cache is nearly full
and then writing out all these changes at once, possibly stalling VM execution for minutes.
This can result in I/O errors in the guest as I/O requests time out there.
3. Physical memory is often wasted as guest operating systems typically have their own I/O
caches, which may result in the data being cached twice (in both the guest and the host
caches) for little effect.
If you decide to disable host I/O caching for the above reasons, VirtualBox uses its own small
cache to buffer writes, but no read caching since this is typically already performed by the guest
OS. In addition, VirtualBox fully supports asynchronous I/O for its virtual SATA, SCSI and SAS
controllers through multiple I/O threads.
Since asynchronous I/O is not supported by IDE controllers, for performance reasons, you may
want to leave host caching enabled for your VM’s virtual IDE controllers.
For this reason, VirtualBox allows you to configure whether the host I/O cache is used for each
I/O controller separately. Either uncheck the “Use host I/O cache” box in the “Storage” settings
for a given virtual storage controller, or use the following VBoxManage command to disable the
host I/O cache for a virtual storage controller:
VBoxManage storagectl "VM name" --name --hostiocache off

See chapter 8.19, VBoxManage storagectl, page 139 for details.
For the above reasons also, VirtualBox now uses SATA controllers by default for new virtual
machines.

5.8 Limiting bandwidth for disk images
Starting with version 4.0, VirtualBox allows for limiting the maximum bandwidth used for asynchronous I/O. Additionally it supports sharing limits through bandwidth groups for several images. It is possible to have more than one such limit.

5 Virtual storage
Limits are configured through VBoxManage. The example below creates a bandwidth group
named “Limit”, sets the limit to 20 MB/s and assigns the group to the attached disks of the VM:
VBoxManage bandwidthctl "VM name" add Limit --type disk --limit 20M
VBoxManage storageattach "VM name" --storagectl "SATA" --port 0 --device 0 --type hdd
--medium disk1.vdi --bandwidthgroup Limit
VBoxManage storageattach "VM name" --storagectl "SATA" --port 1 --device 0 --type hdd
--medium disk2.vdi --bandwidthgroup Limit

All disks in a group share the bandwidth limit, meaning that in the example above the bandwidth of both images combined can never exceed 20 MB/s. However, if one disk doesn’t require
bandwidth the other can use the remaining bandwidth of its group.
The limits for each group can be changed while the VM is running, with changes being picked
up immediately. The example below changes the limit for the group created in the example
above to 10 MB/s:
VBoxManage bandwidthctl "VM name" set Limit --limit 10M

5.9 CD/DVD support
The virtual CD/DVD drive(s) by default support only reading. The medium configuration is
changeable at runtime. You can select between three options to provide the medium data:
• Host Drive defines that the guest can read from the medium in the host drive.
• Image file (typically an ISO file) gives the guest read-only access to the data in the image.
• Empty stands for a drive without an inserted medium.
Changing between the above, or changing a medium in the host drive that is accessed by a
machine, or changing an image file will signal a medium change to the guest operating system,
which can then react to the change (e.g. by starting an installation program).
Medium changes can be prevented by the guest, and VirtualBox reflects that by locking the
host drive if appropriate. You can force a medium removal in such situations via the VirtualBox
GUI or the VBoxManage command line tool. Effectively this is the equivalent of the emergency
eject which many CD/DVD drives provide, with all associated side effects: the guest OS can issue
error messages, just like on real hardware, and guest applications may misbehave. Use this with
caution.
Note: The identification string of the drive provided to the guest (which, in the guest,
would be displayed by configuration tools such as the Windows Device Manager) is
always “VBOX CD-ROM”, irrespective of the current configuration of the virtual drive.
This is to prevent hardware detection from being triggered in the guest operating system every time the configuration is changed.
The standard CD/DVD emulation allows for reading standard data CD and DVD formats only.
As an experimental feature, for additional capabilities, it is possible to give the guest direct access
to the CD/DVD host drive by enabling “passthrough” mode. Depending on the host hardware,
this may enable three things to work, potentially:
• CD/DVD writing from within the guest, if the host DVD drive is a CD/DVD writer;
• playing audio CDs;
• playing encrypted DVDs.

5 Virtual storage
There is a “Passthrough” checkbox in the GUI dialog for configuring the media attached to a
storage controller, or you can use the --passthrough option with VBoxManage storageattach;
see chapter 8.18, VBoxManage storageattach, page 137 for details.
Even if pass-through is enabled, unsafe commands, such as updating the drive firmware, will
be blocked. Video CD formats are never supported, not even in passthrough mode, and cannot
be played from a virtual machine.
On Solaris hosts, pass-through requires running VirtualBox with real root permissions due to
security measures enforced by the host.

5.10 iSCSI servers
iSCSI stands for “Internet SCSI” and is a standard that allows for using the SCSI protocol over
Internet (TCP/IP) connections. Especially with the advent of Gigabit Ethernet, it has become
affordable to attach iSCSI storage servers simply as remote hard disks to a computer network. In
iSCSI terminology, the server providing storage resources is called an “iSCSI target”, while the
client connecting to the server and accessing its resources is called “iSCSI initiator”.
VirtualBox can transparently present iSCSI remote storage to a virtual machine as a virtual
hard disk. The guest operating system will not see any difference between a virtual disk image
(VDI file) and an iSCSI target. To achieve this, VirtualBox has an integrated iSCSI initiator.
VirtualBox’s iSCSI support has been developed according to the iSCSI standard and should
work with all standard-conforming iSCSI targets. To use an iSCSI target with VirtualBox, you
must use the command line; see chapter 8.18, VBoxManage storageattach, page 137.

6 Virtual networking
As briefly mentioned in chapter 3.8, Network settings, page 54, VirtualBox provides up to eight
virtual PCI Ethernet cards for each virtual machine. For each such card, you can individually
select
1. the hardware that will be virtualized as well as
2. the virtualization mode that the virtual card will be operating in with respect to your
physical networking hardware on the host.
Four of the network cards can be configured in the “Network” section of the settings dialog
in the graphical user interface of VirtualBox. You can configure all eight network cards on the
command line via VBoxManage modifyvm; see chapter 8.8, VBoxManage modifyvm, page 125.
This chapter explains the various networking settings in more detail.

6.1 Virtual networking hardware
For each card, you can individually select what kind of hardware will be presented to the virtual
machine. VirtualBox can virtualize the following six types of networking hardware:
• AMD PCNet PCI II (Am79C970A);
• AMD PCNet FAST III (Am79C973, the default);
• Intel PRO/1000 MT Desktop (82540EM);
• Intel PRO/1000 T Server (82543GC);
• Intel PRO/1000 MT Server (82545EM);
• Paravirtualized network adapter (virtio-net).
The PCNet FAST III is the default because it is supported by nearly all operating systems out
of the box, as well as the GNU GRUB boot manager. As an exception, the Intel PRO/1000 family
adapters are chosen for some guest operating system types that no longer ship with drivers for
the PCNet card, such as Windows Vista.
The Intel PRO/1000 MT Desktop type works with Windows Vista and later versions. The T
Server variant of the Intel PRO/1000 card is recognized by Windows XP guests without additional
driver installation. The MT Server variant facilitates OVF imports from other platforms.
The “Paravirtualized network adapter (virtio-net)“ is special. If you select this, then
VirtualBox does not virtualize common networking hardware (that is supported by common
guest operating systems out of the box). Instead, VirtualBox then expects a special software
interface for virtualized environments to be provided by the guest, thus avoiding the complexity
of emulating networking hardware and improving network performance. Starting with version
3.1, VirtualBox provides support for the industry-standard “virtio” networking drivers, which are
part of the open-source KVM project.
The “virtio” networking drivers are available for the following guest operating systems:
• Linux kernels version 2.6.25 or later can be configured to provide virtio support; some
distributions also back-ported virtio to older kernels.

6 Virtual networking
• For Windows 2000, XP and Vista, virtio drivers can be downloaded and installed from the
KVM project web page.1
VirtualBox also has limited support for so-called jumbo frames, i.e. networking packets with
more than 1500 bytes of data, provided that you use the Intel card virtualization and bridged
networking. In other words, jumbo frames are not supported with the AMD networking devices;
in those cases, jumbo packets will silently be dropped for both the transmit and the receive
direction. Guest operating systems trying to use this feature will observe this as a packet loss,
which may lead to unexpected application behavior in the guest. This does not cause problems
with guest operating systems in their default configuration, as jumbo frames need to be explicitly
enabled.

6.2 Introduction to networking modes
Each of the eight networking adapters can be separately configured to operate in one of the
following modes:
Not attached In this mode, VirtualBox reports to the guest that a network card is present, but
that there is no connection – as if no Ethernet cable was plugged into the card. This way
it is possible to “pull” the virtual Ethernet cable and disrupt the connection, which can
be useful to inform a guest operating system that no network connection is available and
enforce a reconfiguration.
Network Address Translation (NAT) If all you want is to browse the Web, download files and
view e-mail inside the guest, then this default mode should be sufficient for you, and you
can safely skip the rest of this section. Please note that there are certain limitations when
using Windows file sharing (see chapter 6.3.3, NAT limitations, page 95 for details).
NAT Network The NAT network is a new NAT flavour introduced in VirtualBox 4.3. See chapter
6.4, Network Address Translation Service (experimental), page 96 for details.
Bridged networking This is for more advanced networking needs such as network simulations
and running servers in a guest. When enabled, VirtualBox connects to one of your installed
network cards and exchanges network packets directly, circumventing your host operating
system’s network stack.
Internal networking This can be used to create a different kind of software-based network
which is visible to selected virtual machines, but not to applications running on the host or
to the outside world.
Host-only networking This can be used to create a network containing the host and a set of
virtual machines, without the need for the host’s physical network interface. Instead, a
virtual network interface (similar to a loopback interface) is created on the host, providing
connectivity among virtual machines and the host.
Generic networking Rarely used modes share the same generic network interface, by allowing
the user to select a driver which can be included with VirtualBox or be distributed in an
extension pack.
At the moment there are potentially two available sub-modes:
UDP Tunnel This can be used to interconnect virtual machines running on different hosts
directly, easily and transparently, over existing network infrastructure.
VDE (Virtual Distributed Ethernet) networking This option can be used to connect to a
Virtual Distributed Ethernet switch on a Linux or a FreeBSD host. At the moment this
needs compiling VirtualBox from sources, as the Oracle packages do not include it.
1 http://www.linux-kvm.org/page/WindowsGuestDrivers.

6 Virtual networking
The following sections describe the available network modes in more detail.

6.3 Network Address Translation (NAT)
Network Address Translation (NAT) is the simplest way of accessing an external network from
a virtual machine. Usually, it does not require any configuration on the host network and guest
system. For this reason, it is the default networking mode in VirtualBox.
A virtual machine with NAT enabled acts much like a real computer that connects to the
Internet through a router. The “router”, in this case, is the VirtualBox networking engine, which
maps traffic from and to the virtual machine transparently. In VirtualBox this router is placed
between each virtual machine and the host. This separation maximizes security since by default
virtual machines cannot talk to each other.
The disadvantage of NAT mode is that, much like a private network behind a router, the virtual
machine is invisible and unreachable from the outside internet; you cannot run a server this way
unless you set up port forwarding (described below).
The network frames sent out by the guest operating system are received by VirtualBox’s NAT
engine, which extracts the TCP/IP data and resends it using the host operating system. To an
application on the host, or to another computer on the same network as the host, it looks like
the data was sent by the VirtualBox application on the host, using an IP address belonging to the
host. VirtualBox listens for replies to the packages sent, and repacks and resends them to the
guest machine on its private network.
The virtual machine receives its network address and configuration on the private network
from a DHCP server integrated into VirtualBox. The IP address thus assigned to the virtual
machine is usually on a completely different network than the host. As more than one card of
a virtual machine can be set up to use NAT, the first card is connected to the private network
10.0.2.0, the second card to the network 10.0.3.0 and so on. If you need to change the guestassigned IP range for some reason, please refer to chapter 9.11, Fine-tuning the VirtualBox NAT
engine, page 174.

6.3.1 Configuring port forwarding with NAT
As the virtual machine is connected to a private network internal to VirtualBox and invisible
to the host, network services on the guest are not accessible to the host machine or to other
computers on the same network. However, like a physical router, VirtualBox can make selected
services available to the world outside the guest through port forwarding. This means that
VirtualBox listens to certain ports on the host and resends all packets which arrive there to the
guest, on the same or a different port.
To an application on the host or other physical (or virtual) machines on the network, it looks as
though the service being proxied is actually running on the host. This also means that you cannot
run the same service on the same ports on the host. However, you still gain the advantages of
running the service in a virtual machine – for example, services on the host machine or on other
virtual machines cannot be compromised or crashed by a vulnerability or a bug in the service,
and the service can run in a different operating system than the host system.
To configure Port Forwarding you can use the graphical Port Forwarding editor which can be
found in the Network Settings dialog for Network Adaptors configured to use NAT. Here you can
map host ports to guest ports to allow network traffic to be routed to a specific port in the guest.
Alternatively command line tool VBoxManage could be used; for details, please refer to chapter
8.8, VBoxManage modifyvm, page 125.
You will need to know which ports on the guest the service uses and to decide which ports
to use on the host (often but not always you will want to use the same ports on the guest and
on the host). You can use any ports on the host which are not already in use by a service. For
example, to set up incoming NAT connections to an ssh server in the guest, use the following
command:

6 Virtual networking
VBoxManage modifyvm "VM name" --natpf1 "guestssh,tcp,,2222,,22"

With the above example, all TCP traffic arriving on port 2222 on any host interface will be
forwarded to port 22 in the guest. The protocol name tcp is a mandatory attribute defining
which protocol should be used for forwarding (udp could also be used). The name guestssh is
purely descriptive and will be auto-generated if omitted. The number after --natpf denotes the
network card, like in other parts of VBoxManage.
To remove this forwarding rule again, use the following command:
VBoxManage modifyvm "VM name" --natpf1 delete "guestssh"

If for some reason the guest uses a static assigned IP address not leased from the built-in DHCP
server, it is required to specify the guest IP when registering the forwarding rule:
VBoxManage modifyvm "VM name" --natpf1 "guestssh,tcp,,2222,10.0.2.19,22"

This example is identical to the previous one, except that the NAT engine is being told that the
guest can be found at the 10.0.2.19 address.
To forward all incoming traffic from a specific host interface to the guest, specify the IP of that
host interface like this:
VBoxManage modifyvm "VM name" --natpf1 "guestssh,tcp,127.0.0.1,2222,,22"

This forwards all TCP traffic arriving on the localhost interface (127.0.0.1) via port 2222 to port
22 in the guest.
It is possible to configure incoming NAT connections while the VM is running, see chapter
8.13, VBoxManage controlvm, page 134.

6.3.2 PXE booting with NAT
PXE booting is now supported in NAT mode. The NAT DHCP server provides a boot file
name of the form vmname.pxe if the directory TFTP exists in the directory where the user’s
VirtualBox.xml file is kept. It is the responsibility of the user to provide vmname.pxe.

6.3.3 NAT limitations
There are four limitations of NAT mode which users should be aware of:
ICMP protocol limitations: Some frequently used network debugging tools (e.g. ping or
tracerouting) rely on the ICMP protocol for sending/receiving messages. While ICMP support has been improved with VirtualBox 2.1 (ping should now work), some other tools
may not work reliably.
Receiving of UDP broadcasts is not reliable: The guest does not reliably receive broadcasts,
since, in order to save resources, it only listens for a certain amount of time after the guest
has sent UDP data on a particular port. As a consequence, NetBios name resolution based
on broadcasts does not always work (but WINS always works). As a workaround, you can
use the numeric IP of the desired server in the \\server\share notation.
Protocols such as GRE are unsupported: Protocols other than TCP and UDP are not supported. This means some VPN products (e.g. PPTP from Microsoft) cannot be used. There
are other VPN products which use simply TCP and UDP.
Forwarding host ports < 1024 impossible: On Unix-based hosts (e.g. Linux, Solaris, Mac OS
X) it is not possible to bind to ports below 1024 from applications that are not run by root.
As a result, if you try to configure such a port forwarding, the VM will refuse to start.
These limitations normally don’t affect standard network use. But the presence of NAT has
also subtle effects that may interfere with protocols that are normally working. One example is
NFS, where the server is often configured to refuse connections from non-privileged ports (i.e.
ports not below 1024).

6 Virtual networking

6.4 Network Address Translation Service (experimental)
The Network Address Translation (NAT) service works in a similar way to a home router, grouping the systems using it into a network and preventing systems outside of this network from
directly accessing systems inside it, but letting systems inside communicate with each other and
with systems outside using TCP and UDP over IPv4 and IPv6.
A NAT service is attached to an internal network. Virtual machines which are to make use of it
should be attached to that internal network. The name of internal network is chosen when the
NAT service is created and the internal network will be created if it does not already exist. An
example command to create a NAT network is:
VBoxManage natnetwork add -t nat-int-network -n "192.168.15.0/24" -e

Here, “nat-int-network” is the name of the internal network to be used and “192.168.15.0/24”
is the network address and mask of the NAT service interface. By default in this static configuration the gateway will be assigned the address 192.168.15.1 (the address following the interface
address), though this is subject to change. To attach a DHCP server to the internal network, we
modify the example as follows:
VBoxManage natnetwork add -t nat-int-network -n "192.168.15.0/24" -e -h on

or to add a DHCP server to the network after creation:
VBoxManage natnetwork modify -t nat-int-network -h on

To disable it again, use:
VBoxManage natnetwork modify -t nat-int-network -h off

DHCP server provides list of registered nameservers, but doesn’t map servers from 127/8
network.
To start the NAT service, use the following command:
VBoxManage natnetwork start -t nat-int-network

If the network has a DHCP server attached then it will start together with the NAT network
service.
VBoxManage natnetwork stop -t nat-int-network

stops the NAT network service, together with DHCP server if any.
To delete the NAT network service use:
VBoxManage natnetwork remove -t nat-int-network

This command does not remove the DHCP server if one is enabled on the internal network.
Port-forwarding is supported (using the “-p” switch for IPv4 and “-P” for IPv6):
VBoxManage natnetwork modify -t nat-int-network -p "ssh:tcp:[]:10022:[192.168.15.15]:22"

This adds a port-forwarding rule from the host’s TCP 10022 port to the port 22 on the guest
with IP address 192.168.15.15. To delete the rule, use:
VBoxManage natnetwork modify -t nat-int-network -p delete ssh

It’s possible to bind NAT service to specified interface:
VBoxManage setextradata global "NAT/win-nat-test-0/SourceIp4" 192.168.1.185

To see the list of registered NAT networks, use:
VBoxManage list natnetworks

6 Virtual networking

6.5 Bridged networking
With bridged networking, VirtualBox uses a device driver on your host system that filters data
from your physical network adapter. This driver is therefore called a “net filter” driver. This
allows VirtualBox to intercept data from the physical network and inject data into it, effectively
creating a new network interface in software. When a guest is using such a new software interface, it looks to the host system as though the guest were physically connected to the interface
using a network cable: the host can send data to the guest through that interface and receive
data from it. This means that you can set up routing or bridging between the guest and the rest
of your network.
For this to work, VirtualBox needs a device driver on your host system. The way bridged networking works has been completely rewritten with VirtualBox 2.0 and 2.1, depending on the host
operating system. From the user perspective, the main difference is that complex configuration
is no longer necessary on any of the supported host operating systems.2
Note: Even though TAP is no longer necessary on Linux with bridged networking, you
can still use TAP interfaces for certain advanced setups, since you can connect a VM to
any host interface – which could also be a TAP interface.
To enable bridged networking, all you need to do is to open the Settings dialog of a virtual
machine, go to the “Network” page and select “Bridged network” in the drop down list for the
“Attached to” field. Finally, select desired host interface from the list at the bottom of the page,
which contains the physical network interfaces of your systems. On a typical MacBook, for
example, this will allow you to select between “en1: AirPort” (which is the wireless interface)
and “en0: Ethernet”, which represents the interface with a network cable.
Note: Bridging to a wireless interface is done differently from bridging to a wired interface, because most wireless adapters do not support promiscuous mode. All traffic
has to use the MAC address of the host’s wireless adapter, and therefore VirtualBox
needs to replace the source MAC address in the Ethernet header of an outgoing packet
to make sure the reply will be sent to the host interface. When VirtualBox sees an incoming packet with a destination IP address that belongs to one of the virtual machine
adapters it replaces the destination MAC address in the Ethernet header with the VM
adapter’s MAC address and passes it on. VirtualBox examines ARP and DHCP packets
in order to learn the IP addresses of virtual machines.
Depending on your host operating system, the following limitations should be kept in mind:
• On Macintosh hosts, functionality is limited when using AirPort (the Mac’s wireless networking) for bridged networking. Currently, VirtualBox supports only IPv4 over AirPort.
For other protocols such as IPv6 and IPX, you must choose a wired interface.
• On Linux hosts, functionality is limited when using wireless interfaces for bridged networking. Currently, VirtualBox supports only IPv4 over wireless. For other protocols such
as IPv6 and IPX, you must choose a wired interface.
Also, setting the MTU to less than 1500 bytes on wired interfaces provided by the sky2
driver on the Marvell Yukon II EC Ultra Ethernet NIC is known to cause packet losses
under certain conditions.
2 For

Mac OS X and Solaris hosts, net filter drivers were already added in VirtualBox 2.0 (as initial support for Host
Interface Networking on these platforms). With VirtualBox 2.1, net filter drivers were also added for the Windows
and Linux hosts, replacing the mechanisms previously present in VirtualBox for those platforms; especially on Linux,
the earlier method required creating TAP interfaces and bridges, which was complex and varied from one distribution
to the next. None of this is necessary anymore. Bridged network was formerly called “Host Interface Networking”
and has been renamed with version 2.2 without any change in functionality.

6 Virtual networking
Some adapters strip VLAN tags in hardware. This does not allow to use VLAN trunking between VM and the external network with pre-2.6.27 Linux kernels nor with host operating
systems other than Linux.
• On Solaris hosts, there is no support for using wireless interfaces. Filtering guest traffic
using IPFilter is also not completely supported due to technical restrictions of the Solaris
networking subsystem. These issues would be addressed in a future release of Solaris 11.
Starting with VirtualBox 4.1, on Solaris 11 hosts (build 159 and above), it is possible to use
Solaris’ Crossbow Virtual Network Interfaces (VNICs) directly with VirtualBox without any
additional configuration other than each VNIC must be exclusive for every guest network
interface.
Starting with VirtualBox 2.0.4 and up to VirtualBox 4.0, VNICs can be used but with the
following caveats:
– A VNIC cannot be shared between multiple guest network interfaces, i.e. each guest
network interface must have its own, exclusive VNIC.
– The VNIC and the guest network interface that uses the VNIC must be assigned identical MAC addresses.
When using VLAN interfaces with VirtualBox, they must be named according to the PPAhack naming scheme (e.g. “e1000g513001”), as otherwise the guest may receive packets
in an unexpected format.

6.6 Internal networking
Internal Networking is similar to bridged networking in that the VM can directly communicate
with the outside world. However, the “outside world” is limited to other VMs on the same host
which connect to the same internal network.
Even though technically, everything that can be done using internal networking can also be
done using bridged networking, there are security advantages with internal networking. In
bridged networking mode, all traffic goes through a physical interface of the host system. It is
therefore possible to attach a packet sniffer (such as Wireshark) to the host interface and log all
traffic that goes over it. If, for any reason, you prefer two or more VMs on the same machine
to communicate privately, hiding their data from both the host system and the user, bridged
networking therefore is not an option.
Internal networks are created automatically as needed, i.e. there is no central configuration.
Every internal network is identified simply by its name. Once there is more than one active virtual
network card with the same internal network ID, the VirtualBox support driver will automatically
“wire” the cards and act as a network switch. The VirtualBox support driver implements a
complete Ethernet switch and supports both broadcast/multicast frames and promiscuous mode.
In order to attach a VM’s network card to an internal network, set its networking mode to
“internal networking”. There are two ways to accomplish this:
• You can use a VM’s “Settings” dialog in the VirtualBox graphical user interface. In the
“Networking” category of the settings dialog, select “Internal Networking” from the dropdown list of networking modes. Now select the name of an existing internal network from
the drop-down below or enter a new name into the entry field.
• You can use
VBoxManage modifyvm "VM name" --nic intnet

Optionally, you can specify a network name with the command
VBoxManage modifyvm "VM name" --intnet "network name"

6 Virtual networking
If you do not specify a network name, the network card will be attached to the network
intnet by default.
Unless you configure the (virtual) network cards in the guest operating systems that are participating in the internal network to use static IP addresses, you may want to use the DHCP server
that is built into VirtualBox to manage IP addresses for the internal network. Please see chapter
8.35, VBoxManage dhcpserver, page 156 for details.
As a security measure, the Linux implementation of internal networking only allows VMs
running under the same user ID to establish an internal network.

6.7 Host-only networking
Host-only networking is another networking mode that was added with version 2.2 of VirtualBox.
It can be thought of as a hybrid between the bridged and internal networking modes: as with
bridged networking, the virtual machines can talk to each other and the host as if they were
connected through a physical Ethernet switch. Similarly, as with internal networking however, a
physical networking interface need not be present, and the virtual machines cannot talk to the
world outside the host since they are not connected to a physical networking interface.
Instead, when host-only networking is used, VirtualBox creates a new software interface on
the host which then appears next to your existing network interfaces. In other words, whereas
with bridged networking an existing physical interface is used to attach virtual machines to,
with host-only networking a new “loopback” interface is created on the host. And whereas with
internal networking, the traffic between the virtual machines cannot be seen, the traffic on the
“loopback” interface on the host can be intercepted.
Host-only networking is particularly useful for preconfigured virtual appliances, where multiple virtual machines are shipped together and designed to cooperate. For example, one virtual
machine may contain a web server and a second one a database, and since they are intended
to talk to each other, the appliance can instruct VirtualBox to set up a host-only network for the
two. A second (bridged) network would then connect the web server to the outside world to
serve data to, but the outside world cannot connect to the database.
To change a virtual machine’s virtual network interface to “host only” mode:
• either go to the “Network” page in the virtual machine’s settings notebook in the graphical
user interface and select “Host-only networking”, or
• on the command line, type VBoxManage modifyvm "VM name" --nic hostonly; see
chapter 8.8, VBoxManage modifyvm, page 125 for details.
For host-only networking, like with internal networking, you may find the DHCP server useful
that is built into VirtualBox. This can be enabled to then manage the IP addresses in the host-only
network since otherwise you would need to configure all IP addresses statically.
• In the VirtualBox graphical user interface, you can configure all these items in the global
settings via “File” -> “Settings” -> “Network”, which lists all host-only networks which are
presently in use. Click on the network name and then on the “Edit” button to the right, and
you can modify the adapter and DHCP settings.
• Alternatively, you can use VBoxManage dhcpserver on the command line; please see chapter 8.35, VBoxManage dhcpserver, page 156 for details.

Note: On Linux and Mac OS X hosts the number of host-only interfaces is limited to
128. There is no such limit for Solaris and Windows hosts.

6 Virtual networking

6.8 UDP Tunnel networking
This networking mode allows to interconnect virtual machines running on different hosts.
Technically this is done by encapsulating Ethernet frames sent or received by the guest network
card into UDP/IP datagrams, and sending them over any network available to the host.
UDP Tunnel mode has three parameters:
Source UDP port The port on which the host listens. Datagrams arriving on this port from any
source address will be forwarded to the receiving part of the guest network card.
Destination address IP address of the target host of the transmitted data.
Destination UDP port Port number to which the transmitted data is sent.
When interconnecting two virtual machines on two different hosts, their IP addresses must be
swapped. On single host, source and destination UDP ports must be swapped.
In the following example host 1 uses the IP address 10.0.0.1 and host 2 uses IP address
10.0.0.2. Configuration via command-line:
VBoxManage
VBoxManage
VBoxManage
VBoxManage
VBoxManage

modifyvm
modifyvm
modifyvm
modifyvm
modifyvm

"VM
"VM
"VM
"VM
"VM

01
01
01
01
01

on
on
on
on
on

host
host
host
host
host

1"
1"
1"
1"
1"

--nic generic
--nicgenericdrv UDPTunnel
--nicproperty dest=10.0.0.2
--nicproperty sport=10001
--nicproperty dport=10002

VBoxManage
VBoxManage
VBoxManage
VBoxManage
VBoxManage

modifyvm
modifyvm
modifyvm
modifyvm
modifyvm

"VM
"VM
"VM
"VM
"VM

02
02
02
02
02

on
on
on
on
on

host
host
host
host
host

2"
2"
2"
2"
2"

--nic generic
--nicgenericdrv UDPTunnel
--nicproperty dest=10.0.0.1
--nicproperty sport=10002
--nicproperty dport=10001

and

Of course, you can always interconnect two virtual machines on the same host, by setting the
destination address parameter to 127.0.0.1 on both. It will act similarly to “Internal network” in
this case, however the host can see the network traffic which it could not in the normal Internal
network case.
Note: On Unix-based hosts (e.g. Linux, Solaris, Mac OS X) it is not possible to bind to
ports below 1024 from applications that are not run by root. As a result, if you try to
configure such a source UDP port, the VM will refuse to start.

6.9 VDE networking
Virtual Distributed Ethernet (VDE3 ) is a flexible, virtual network infrastructure system, spanning
across multiple hosts in a secure way. It allows for L2/L3 switching, including spanning-tree
protocol, VLANs, and WAN emulation. It is an optional part of VirtualBox which is only included
in the source code.
The basic building blocks of the infrastructure are VDE switches, VDE plugs and VDE wires
which inter-connect the switches.
The VirtualBox VDE driver has one parameter:
VDE network The name of the VDE network switch socket to which the VM will be connected.
The following basic example shows how to connect a virtual machine to a VDE switch:
3 VDE

is a project developed by Renzo Davoli, Associate Professor at the University of Bologna, Italy.

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6 Virtual networking
1. Create a VDE switch:
vde_switch -s /tmp/switch1

2. Configuration via command-line:
VBoxManage modifyvm "VM name" --nic generic
VBoxManage modifyvm "VM name" --nicgenericdrv VDE

To connect to automatically allocated switch port, use:
VBoxManage modifyvm "VM name" --nicproperty network=/tmp/switch1

To connect to specific switch port , use:
VBoxManage modifyvm "VM name" --nicproperty network=/tmp/switch1[]

The latter option can be useful for VLANs.
3. Optionally map between VDE switch port and VLAN: (from switch CLI)
vde$ vlan/create
vde$ port/setvlan

VDE is available on Linux and FreeBSD hosts only. It is only available if the VDE software
and the VDE plugin library from the VirtualSquare project are installed on the host system4 . For
more information on setting up VDE networks, please see the documentation accompanying the
software.5

6.10 Limiting bandwidth for network I/O
Starting with version 4.2, VirtualBox allows for limiting the maximum bandwidth used for network transmission. Several network adapters of one VM may share limits through bandwidth
groups. It is possible to have more than one such limit.
Note: VirtualBox shapes VM traffic only in the transmit direction, delaying the packets
being sent by virtual machines. It does not limit the traffic being received by virtual
machines.
Limits are configured through VBoxManage. The example below creates a bandwidth group
named “Limit”, sets the limit to 20 Mbit/s and assigns the group to the first and second adapters
of the VM:
VBoxManage bandwidthctl "VM name" add Limit --type network --limit 20m
VBoxManage modifyvm "VM name" --nicbandwidthgroup1 Limit
VBoxManage modifyvm "VM name" --nicbandwidthgroup2 Limit

All adapters in a group share the bandwidth limit, meaning that in the example above the
bandwidth of both adapters combined can never exceed 20 Mbit/s. However, if one adapter
doesn’t require bandwidth the other can use the remaining bandwidth of its group.
The limits for each group can be changed while the VM is running, with changes being picked
up immediately. The example below changes the limit for the group created in the example
above to 100 Kbit/s:
VBoxManage bandwidthctl "VM name" set Limit --limit 100k

To completely disable shaping for the first adapter of VM use the following command:
4 For

Linux hosts, the shared library libvdeplug.so must be available in the search path for shared libraries

5 http://wiki.virtualsquare.org/wiki/index.php/VDE_Basic_Networking.

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VBoxManage modifyvm "VM name" --nicbandwidthgroup1 none

It is also possible to disable shaping for all adapters assigned to a bandwidth group while VM
is running, by specifying the zero limit for the group. For example, for the bandwidth group
named “Limit” use:
VBoxManage bandwidthctl "VM name" set Limit --limit 0

6.11 Improving network performance
VirtualBox provides a variety of virtual network adapters that can be “attached” to the host’s
network in a number of ways. Depending on which types of adapters and attachments are
used the network performance will be different. Performance-wise the virtio network adapter
is preferable over Intel PRO/1000 emulated adapters, which are preferred over PCNet family
of adapters. Both virtio and Intel PRO/1000 adapters enjoy the benefit of segmentation and
checksum offloading. Segmentation offloading is essential for high performance as it allows for
less context switches, dramatically increasing the sizes of packets that cross VM/host boundary.
Note: Neither virtio nor Intel PRO/1000 drivers for Windows XP support segmentation
offloading. Therefore Windows XP guests never reach the same transmission rates as
other guest types. Refer to MS Knowledge base article 842264 for additional information.
Three attachment types: internal, bridged and host-only, have nearly identical performance,
the internal type being a little bit faster and using less CPU cycles as the packets never reach the
host’s network stack. The NAT attachment is the slowest (and safest) of all attachment types as
it provides network address translation. The generic driver attachment is special and cannot be
considered as an alternative to other attachment types.
The number of CPUs assigned to VM does not improve network performance and in some cases
may hurt it due to increased concurrency in the guest.
Here is the short summary of things to check in order to improve network performance:
1. Whenever possible use virtio network adapter, otherwise use one of Intel PRO/1000
adapters;
2. Use bridged attachment instead of NAT;
3. Make sure segmentation offloading is enabled in the guest OS. Usually it will be enabled by
default. You can check and modify offloading settings using ethtool command in Linux
guests.

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7.1 Remote display (VRDP support)
VirtualBox can display virtual machines remotely, meaning that a virtual machine can execute
on one computer even though the machine will be displayed on a second computer, and the
machine will be controlled from there as well, as if the virtual machine was running on that
second computer.
For maximum flexibility, starting with VirtualBox 4.0, VirtualBox implements remote machine
display through a generic extension interface, the VirtualBox Remote Desktop Extension (VRDE).
The base open-source VirtualBox package only provides this interface, while implementations
can be supplied by third parties with VirtualBox extension packages, which must be installed
separately from the base package. See chapter 1.5, Installing VirtualBox and extension packs,
page 16 for more information.
Oracle provides support for the VirtualBox Remote Display Protocol (VRDP) in such a
VirtualBox extension package. When this package is installed, VirtualBox versions 4.0 and later
support VRDP the same way as binary (non-open-source) versions of VirtualBox before 4.0 did.
VRDP is a backwards-compatible extension to Microsoft’s Remote Desktop Protocol (RDP). As
a result, you can use any standard RDP client to control the remote VM.
Even when the extension is installed, the VRDP server is disabled by default. It can easily be
enabled on a per-VM basis either in the VirtualBox Manager in the “Display” settings (see chapter
3.5, Display settings, page 51) or with VBoxManage:
VBoxManage modifyvm "VM name" --vrde on

If you use VBoxHeadless (described further below), VRDP support will be automatically enabled since VBoxHeadless has no other means of output.
By default, the VRDP server uses TCP port 3389. You will need to change the default port if
you run more than one VRDP server, since the port can only be used by one server at a time; you
might also need to change it on Windows hosts since the default port might already be used by
the RDP server that is built into Windows itself. Ports 5000 through 5050 are typically not used
and might be a good choice.
The port can be changed either in the “Display” settings of the graphical user interface or
with --vrdeport option of the VBoxManage modifyvm command. You can specify a commaseparated list of ports or ranges of ports. Use a dash between two port numbers to specify a
range. The VRDP server will bind to one of available ports from the specified list. For example,
VBoxManage modifyvm "VM name" --vrdeport 5000,5010-5012 will configure the server to
bind to one of the ports 5000, 5010, 5011 or 5012. See chapter 8.8.4, Remote machine settings,
page 130 for details.
The actual port used by a running VM can be either queried with VBoxManage showvminfo
command or seen in the GUI on the “Runtime” tab of the “Session Information Dialog”, which is
accessible via the “Machine” menu of the VM window.
Support for IPv6 has been implemented in VirtualBox 4.3. If the host OS supports IPv6 the
VRDP server will automatically listen for IPv6 connections in addition to IPv4.

7.1.1 Common third-party RDP viewers
Since VRDP is backwards-compatible to RDP, you can use any standard RDP viewer to connect
to such a remote virtual machine (examples follow below). For this to work, you must specify

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the IP address of your host system (not of the virtual machine!) as the server address to connect
to, as well as the port number that the VRDP server is using.
Here follow examples for the most common RDP viewers:
• On Windows, you can use the Microsoft Terminal Services Connector (mstsc.exe) that
ships with Windows. You can start it by bringing up the “Run” dialog (press the Windows
key and “R”) and typing “mstsc”. You can also find it under “Start” -> “All Programs” ->
“Accessories” -> “Remote Desktop Connection”. If you use the “Run” dialog, you can type
in options directly:
mstsc 1.2.3.4:3389

Replace 1.2.3.4 with the host IP address, and 3389 with a different port if necessary.
Note: IPv6 address must be enclosed in square brackets to specify a port. For example:
mstsc [fe80::1:2:3:4]:3389

Note: When connecting to localhost in order to test the connection, the addresses
localhost and 127.0.0.1 might not work using mstsc.exe. Instead, the address
127.0.0.2[:3389] has to be used.

• On other systems, you can use the standard open-source rdesktop program. This ships
with most Linux distributions, but VirtualBox also comes with a modified variant of rdesktop for remote USB support (see chapter 7.1.4, Remote USB, page 107 below).
With rdesktop, use a command line such as the following:
rdesktop -a 16 -N 1.2.3.4:3389

As said for the Microsoft viewer above, replace 1.2.3.4 with the host IP address, and
3389 with a different port if necessary. The -a 16 option requests a color depth of 16
bits per pixel, which we recommend. (For best performance, after installation of the guest
operating system, you should set its display color depth to the same value). The -N option
enables use of the NumPad keys.
• If you run the KDE desktop, you might prefer krdc, the KDE RDP viewer. The command
line would look like this:
krdc rdp://1.2.3.4:3389

Again, replace 1.2.3.4 with the host IP address, and 3389 with a different port if necessary.
The “rdp://“ bit is required with krdc to switch it into RDP mode.
• With Sun Ray thin clients you can use uttsc, which is part of the Sun Ray Windows
Connector package. See the corresponding documentation for details.

7.1.2 VBoxHeadless, the remote desktop server
While any VM started from the VirtualBox Manager is capable of running virtual machines remotely, it is not convenient to have to run the full-fledged GUI if you never want to have VMs
displayed locally in the first place. In particular, if you are running server hardware whose only
purpose is to host VMs, and all your VMs are supposed to run remotely over VRDP, then it is
pointless to have a graphical user interface on the server at all – especially since, on a Linux or
Solaris host, the VirtualBox manager comes with dependencies on the Qt and SDL libraries. This
is inconvenient if you would rather not have the X Window system on your server at all.

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VirtualBox therefore comes with yet another front-end called VBoxHeadless, which produces
no visible output on the host at all, but instead only delivers VRDP data. This front-end has no
dependencies on the X Window system on Linux and Solaris hosts.1
To start a virtual machine with VBoxHeadless, you have three options:
• You can use
VBoxManage startvm "VM name" --type headless

The extra --type option causes VirtualBox to use VBoxHeadless as the front-end to the
internal virtualization engine instead of the Qt front-end.
• One alternative is to use VBoxHeadless directly, as follows:
VBoxHeadless --startvm

This way of starting the VM helps troubleshooting problems reported by VBoxManage
startvm ... because you can see sometimes more detailed error messages, especially
for early failures before the VM execution is started. In normal situations VBoxManage
startvm is preferred since it runs the VM directly as a background process which has to be
done explicitly when directly starting VBoxHeadless.
• The other alternative is to start VBoxHeadless from the VirtualBox Manager GUI, by holding the Shift key when starting a virtual machine.
Note that when you use VBoxHeadless to start a VM, since the headless server has no other
means of output, the VRDP server will always be enabled, regardless of whether you had enabled
the VRDP server in the VM’s settings. If this is undesirable (for example because you want to
access the VM via ssh only), start the VM like this:
VBoxHeadless --startvm --vrde off

To have the VRDP server enabled depending on the VM configuration, as the other front-ends
would, use this:
VBoxHeadless --startvm --vrde config

If you start the VM with VBoxManage startvm ... then the configuration settings of the VM
are always used.

7.1.3 Step by step: creating a virtual machine on a headless server
The following instructions may give you an idea how to create a virtual machine on a headless
server over a network connection. We will create a virtual machine, establish an RDP connection
and install a guest operating system – all without having to touch the headless server. All you
need is the following:
1. VirtualBox on a server machine with a supported host operating system. The VirtualBox
extension pack for the VRDP server must be installed (see the previous section). For the
following example, we will assume a Linux server.
2. An ISO file accessible from the server, containing the installation data for the guest operating system to install (we will assume Windows XP in the following example).
3. A terminal connection to that host through which you can access a command line (e.g. via
ssh).
1 Before VirtualBox 1.6,

the headless server was called VBoxVRDP. For the sake of backwards compatibility, the VirtualBox
installation still installs an executable with that name as well.

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7 Remote virtual machines
4. An RDP viewer on the remote client; see chapter 7.1.1, Common third-party RDP viewers,
page 103 above for examples.
Note again that on the server machine, since we will only use the headless server, neither Qt nor
SDL nor the X Window system will be needed.
1. On the headless server, create a new virtual machine:
VBoxManage createvm --name "Windows XP" --ostype WindowsXP --register

Note that if you do not specify --register, you will have to manually use the registervm
command later.
Note further that you do not need to specify --ostype, but doing so selects some sane
default values for certain VM parameters, for example the RAM size and the type of the
virtual network device. To get a complete list of supported operating systems you can use
VBoxManage list ostypes

2. Make sure the settings for this VM are appropriate for the guest operating system that we
will install. For example:
VBoxManage modifyvm "Windows XP" --memory 256 --acpi on --boot1 dvd --nic1 nat

3. Create a virtual hard disk for the VM (in this case, 10GB in size):
VBoxManage createhd --filename "WinXP.vdi" --size 10000

4. Add an IDE Controller to the new VM:
VBoxManage storagectl "Windows XP" --name "IDE Controller"
--add ide --controller PIIX4

5. Set the VDI file created above as the first virtual hard disk of the new VM:
VBoxManage storageattach "Windows XP" --storagectl "IDE Controller"
--port 0 --device 0 --type hdd --medium "WinXP.vdi"

6. Attach the ISO file that contains the operating system installation that you want to install
later to the virtual machine, so the machine can boot from it:
VBoxManage storageattach "Windows XP" --storagectl "IDE Controller"
--port 0 --device 1 --type dvddrive --medium /full/path/to/iso.iso

7. Start the virtual machine using VBoxHeadless:
VBoxHeadless --startvm "Windows XP"

If everything worked, you should see a copyright notice. If, instead, you are returned to
the command line, then something went wrong.
8. On the client machine, fire up the RDP viewer and try to connect to the server (see chapter
7.1.1, Common third-party RDP viewers, page 103 above for how to use various common
RDP viewers).
You should now be seeing the installation routine of your guest operating system remotely
in the RDP viewer.

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7.1.4 Remote USB
As a special feature on top of the VRDP support, VirtualBox supports remote USB devices over
the wire as well. That is, the VirtualBox guest that runs on one computer can access the USB
devices of the remote computer on which the VRDP data is being displayed the same way as
USB devices that are connected to the actual host. This allows for running virtual machines on
a VirtualBox host that acts as a server, where a client can connect from elsewhere that needs
only a network adapter and a display capable of running an RDP viewer. When USB devices are
plugged into the client, the remote VirtualBox server can access them.
For these remote USB devices, the same filter rules apply as for other USB devices, as described
with chapter 3.10.1, USB settings, page 56. All you have to do is specify “Remote” (or “Any”)
when setting up these rules.
Accessing remote USB devices is only possible if the RDP client supports this extension.
On Linux and Solaris hosts, the VirtualBox installation provides a suitable VRDP client called
rdesktop-vrdp. Recent versions of uttsc, a client tailored for the use with Sun Ray thin clients,
also support accessing remote USB devices. RDP clients for other platforms will be provided in
future VirtualBox versions.
To make a remote USB device available to a VM, rdesktop-vrdp should be started as follows:
rdesktop-vrdp -r usb -a 16 -N my.host.address

Please refer to chapter 12.7.7, USB not working, page 223 for further details on how to properly
set up the permissions for USB devices. Furthermore it is advisable to disable automatic loading
of any host driver on the remote host which might work on USB devices to ensure that the devices
are accessible by the RDP client. If the setup was properly done on the remote host, plug/unplug
events are visible on the VBox.log file of the VM.

7.1.5 RDP authentication
For each virtual machine that is remotely accessible via RDP, you can individually determine if
and how client connections are authenticated. For this, use VBoxManage modifyvm command
with the --vrdeauthtype option; see chapter 8.8, VBoxManage modifyvm, page 125 for a general introduction. Three methods of authentication are available:
• The “null” method means that there is no authentication at all; any client can connect to
the VRDP server and thus the virtual machine. This is, of course, very insecure and only to
be recommended for private networks.
• The “external” method provides external authentication through a special authentication
library. VirtualBox ships with two such authentication libraries:
1. The default authentication library, VBoxAuth, authenticates against user credentials
of the hosts. Depending on the host platform, this means:
– On Linux hosts, VBoxAuth.so authenticates users against the host’s PAM system.
– On Windows hosts, VBoxAuth.dll authenticates users against the host’s WinLogon system.
– On Mac OS X hosts, VBoxAuth.dylib authenticates users against the host’s directory service.2
In other words, the “external” method per default performs authentication with the
user accounts that exist on the host system. Any user with valid authentication credentials is accepted, i.e. the username does not have to correspond to the user running
the VM.
2 Support

for Mac OS X was added in version 3.2.

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7 Remote virtual machines
2. An additional library called VBoxAuthSimple performs authentication against credentials configured in the “extradata” section of a virtual machine’s XML settings file. This
is probably the simplest way to get authentication that does not depend on a running
and supported guest (see below). The following steps are required:
a) Enable VBoxAuthSimple with the following command:
VBoxManage setproperty vrdeauthlibrary "VBoxAuthSimple"

b) To enable the library for a particular VM, you must then switch authentication to
external:
VBoxManage modifyvm "VM name" --vrdeauthtype external

Replace with the VM name or UUID.
c) You will then need to configure users and passwords by writing items into the
machine’s extradata. Since the XML machine settings file, into whose “extradata”
section the password needs to be written, is a plain text file, VirtualBox uses
hashes to encrypt passwords. The following command must be used:
VBoxManage setextradata "VM name" "VBoxAuthSimple/users/"

Replace with the VM name or UUID, with the user name who should
be allowed to log in and with the encrypted password. As an example,
to obtain the hash value for the password “secret”, you can use the following
command:
VBoxManage internalcommands passwordhash "secret"

This will print
2bb80d537b1da3e38bd30361aa855686bde0eacd7162fef6a25fe97bf527a25b

You can then use VBoxManage setextradata to store this value in the machine’s
“extradata” section.
As example, combined together, to set the password for the user “john” and the
machine “My VM” to “secret”, use this command:
VBoxManage setextradata "My VM" "VBoxAuthSimple/users/john"
2bb80d537b1da3e38bd30361aa855686bde0eacd7162fef6a25fe97bf527a25b

• Finally, the “guest” authentication method performs authentication with a special component that comes with the Guest Additions; as a result, authentication is not performed on
the host, but with the guest user accounts.
This method is currently still in testing and not yet supported.
In addition to the methods described above, you can replace the default “external” authentication module with any other module. For this, VirtualBox provides a well-defined interface that
allows you to write your own authentication module. This is described in detail in the VirtualBox
Software Development Kit (SDK) reference; please see chapter 11, VirtualBox programming interfaces, page 208 for details.

7.1.6 RDP encryption
RDP features data stream encryption, which is based on the RC4 symmetric cipher (with keys up
to 128bit). The RC4 keys are being replaced in regular intervals (every 4096 packets).
RDP provides different authentication methods:
1. Historically, RDP4 authentication was used, with which the RDP client does not perform
any checks in order to verify the identity of the server it connects to. Since user credentials can be obtained using a “man in the middle” (MITM) attack, RDP4 authentication is
insecure and should generally not be used.

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7 Remote virtual machines
2. RDP5.1 authentication employs a server certificate for which the client possesses the public
key. This way it is guaranteed that the server possess the corresponding private key. However, as this hard-coded private key became public some years ago, RDP5.1 authentication
is also insecure.
3. RDP5.2 authentication uses the Enhanced RDP Security, which means that an external
security protocol is used to secure the connection. RDP4 and RDP5.1 use Standard RDP
Security. The VRDP server supports Enhanced RDP Security with TLS protocol and, as a
part of TLS handshake, sends the server certificate to the client.
The Security/Method VRDE property sets the desired security method, which is used for
a connection. Valid values are:
• Negotiate - both Enhanced (TLS) and Standard RDP Security connections are allowed. The security method is negotiated with the client. This is the default setting.
• RDP - only Standard RDP Security is accepted.
• TLS - only Enhanced RDP Security is accepted. The client must support TLS.
For example the following command allows a client to use either Standard or Enhanced
RDP Security connection:
vboxmanage modifyvm "VM name" --vrdeproperty "Security/Method=negotiate"

If the Security/Method property is set to either Negotiate or TLS, the TLS protocol
will be automatically used by the server, if the client supports TLS. However, in order to
use TLS the server must possess the Server Certificate, the Server Private Key and the
Certificate Authority (CA) Certificate. The following example shows how to generate a
server certificate.
a) Create a CA self signed certificate:
openssl req -new -x509 -days 365 -extensions v3_ca \
-keyout ca_key_private.pem -out ca_cert.pem

b) Generate a server private key and a request for signing:
openssl genrsa -out server_key_private.pem
openssl req -new -key server_key_private.pem -out server_req.pem

c) Generate the server certificate:
openssl x509 -req -days 365 -in server_req.pem \
-CA ca_cert.pem -CAkey ca_key_private.pem -set_serial 01 -out server_cert.pem

The server must be configured to access the required files:
vboxmanage modifyvm "VM name" \
--vrdeproperty "Security/CACertificate=path/ca_cert.pem"
vboxmanage modifyvm "VM name" \
--vrdeproperty "Security/ServerCertificate=path/server_cert.pem"
vboxmanage modifyvm "VM name" \
--vrdeproperty "Security/ServerPrivateKey=path/server_key_private.pem"

As the client that connects to the server determines what type of encryption will be used, with
rdesktop, the Linux RDP viewer, use the -4 or -5 options.

7.1.7 Multiple connections to the VRDP server
The VRDP server of VirtualBox supports multiple simultaneous connections to the same running
VM from different clients. All connected clients see the same screen output and share a mouse
pointer and keyboard focus. This is similar to several people using the same computer at the
same time, taking turns at the keyboard.
The following command enables multiple connection mode:
VBoxManage modifyvm "VM name" --vrdemulticon on

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7 Remote virtual machines

7.1.8 Multiple remote monitors
To access two or more remote VM displays you have to enable the VRDP multiconnection mode
(see chapter 7.1.7, Multiple connections to the VRDP server, page 109).
The RDP client can select the virtual monitor number to connect to using the domain logon
parameter (-d). If the parameter ends with @ followed by a number, VirtualBox interprets this
number as the screen index. The primary guest screen is selected with @1, the first secondary
screen is @2, etc.
The Microsoft RDP6 client does not let you specify a separate domain name. Instead, use
domain\username in the Username: field – for example, @2\name. name must be supplied, and
must be the name used to log in if the VRDP server is set up to require credentials. If it is not,
you may use any text as the username.

7.1.9 VRDP video redirection
Starting with VirtualBox 3.2, the VRDP server can redirect video streams from the guest to the
RDP client. Video frames are compressed using the JPEG algorithm allowing a higher compression ratio than standard RDP bitmap compression methods. It is possible to increase the
compression ratio by lowering the video quality.
The VRDP server automatically detects video streams in a guest as frequently updated rectangular areas. As a result, this method works with any guest operating system without having to
install additional software in the guest; in particular, the Guest Additions are not required.
On the client side, however, currently only the Windows 7 Remote Desktop Connection client
supports this feature. If a client does not support video redirection, the VRDP server falls back to
regular bitmap updates.
The following command enables video redirection:
VBoxManage modifyvm "VM name" --vrdevideochannel on

The quality of the video is defined as a value from 10 to 100 percent, representing a JPEG
compression level (where lower numbers mean lower quality but higher compression). The
quality can be changed using the following command:
VBoxManage modifyvm "VM name" --vrdevideochannelquality 75

7.1.10 VRDP customization
With VirtualBox 4.0 it is possible to disable display output, mouse and keyboard input, audio,
remote USB or clipboard individually in the VRDP server.
The following commands change corresponding server settings:
VBoxManage
VBoxManage
VBoxManage
VBoxManage
VBoxManage
VBoxManage

modifyvm
modifyvm
modifyvm
modifyvm
modifyvm
modifyvm

"VM
"VM
"VM
"VM
"VM
"VM

name"
name"
name"
name"
name"
name"

--vrdeproperty
--vrdeproperty
--vrdeproperty
--vrdeproperty
--vrdeproperty
--vrdeproperty

Client/DisableDisplay=1
Client/DisableInput=1
Client/DisableUSB=1
Client/DisableAudio=1
Client/DisableClipboard=1
Client/DisableUpstreamAudio=1

To reenable a feature use a similar command without the trailing 1. For example:
VBoxManage modifyvm "VM name" --vrdeproperty Client/DisableDisplay=

These properties were introduced with VirtualBox 3.2.10. However, in the 3.2.x series, it was
necessary to use the following commands to alter these settings instead:
VBoxManage
VBoxManage
VBoxManage
VBoxManage
VBoxManage

setextradata
setextradata
setextradata
setextradata
setextradata

"VM
"VM
"VM
"VM
"VM

name"
name"
name"
name"
name"

"VRDP/Feature/Client/DisableDisplay" 1
"VRDP/Feature/Client/DisableInput" 1
"VRDP/Feature/Client/DisableUSB" 1
"VRDP/Feature/Client/DisableAudio" 1
"VRDP/Feature/Client/DisableClipboard" 1

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7 Remote virtual machines
To reenable a feature use a similar command without the trailing 1. For example:
VBoxManage setextradata "VM name" "VRDP/Feature/Client/DisableDisplay"

7.2 Teleporting
Starting with version 3.1, VirtualBox supports “teleporting” – that is, moving a virtual machine
over a network from one VirtualBox host to another, while the virtual machine is running. This
works regardless of the host operating system that is running on the hosts: you can teleport
virtual machines between Solaris and Mac hosts, for example.
Teleporting requires that a machine be currently running on one host, which is then called
the “source”. The host to which the virtual machine will be teleported will then be called the
“target”; the machine on the target is then configured to wait for the source to contact the target.
The machine’s running state will then be transferred from the source to the target with minimal
downtime.
Teleporting happens over any TCP/IP network; the source and the target only need to agree
on a TCP/IP port which is specified in the teleporting settings.
At this time, there are a few prerequisites for this to work, however:
1. On the target host, you must configure a virtual machine in VirtualBox with exactly the
same hardware settings as the machine on the source that you want to teleport. This does
not apply to settings which are merely descriptive, such as the VM name, but obviously for
teleporting to work, the target machine must have the same amount of memory and other
hardware settings. Otherwise teleporting will fail with an error message.
2. The two virtual machines on the source and the target must share the same storage (hard
disks as well as floppy and CD/DVD images). This means that they either use the same
iSCSI targets or that the storage resides somewhere on the network and both hosts have
access to it via NFS or SMB/CIFS.
This also means that neither the source nor the target machine can have any snapshots.
Then perform the following steps:
1. On the target host, configure the virtual machine to wait for a teleport request to arrive
when it is started, instead of actually attempting to start the machine. This is done with
the following VBoxManage command:
VBoxManage modifyvm --teleporter on --teleporterport

where is the name of the virtual machine on the target host and
is a TCP/IP port number to be used on both the source and the target hosts. For example,
use 6000. For details, see chapter 8.8.5, Teleporting settings, page 131.
2. Start the VM on the target host. You will see that instead of actually running, it will show
a progress dialog. indicating that it is waiting for a teleport request to arrive.
3. Start the machine on the source host as usual. When it is running and you want it to be
teleported, issue the following command on the source host:
VBoxManage controlvm teleport --host --port

where is the name of the virtual machine on the source host (the machine
that is currently running), is the host or IP name of the target host on which
the machine is waiting for the teleport request, and must be the same number as
specified in the command on the target host. For details, see chapter 8.13, VBoxManage
controlvm, page 134.

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7 Remote virtual machines
For testing, you can also teleport machines on the same host; in that case, use “localhost” as
the hostname on both the source and the target host.
Note: In rare cases, if the CPUs of the source and the target are very different, teleporting can fail with an error message, or the target may hang. This may happen
especially if the VM is running application software that is highly optimized to run
on a particular CPU without correctly checking that certain CPU features are actually
present. VirtualBox filters what CPU capabilities are presented to the guest operating
system. Advanced users can attempt to restrict these virtual CPU capabilities with the
VBoxManage --modifyvm --cpuid command; see chapter 8.8.5, Teleporting settings,
page 131.

112

8 VBoxManage
8.1 Introduction
As briefly mentioned in chapter 1.16, Alternative front-ends, page 33, VBoxManage is the
command-line interface to VirtualBox. With it, you can completely control VirtualBox from the
command line of your host operating system. VBoxManage supports all the features that the
graphical user interface gives you access to, but it supports a lot more than that. It exposes really
all the features of the virtualization engine, even those that cannot (yet) be accessed from the
GUI.
You will need to use the command line if you want to
• use a different user interface than the main GUI (for example, VBoxSDL or the VBoxHeadless server);
• control some of the more advanced and experimental configuration settings for a VM.
There are two main things to keep in mind when using VBoxManage: First, VBoxManage must
always be used with a specific “subcommand”, such as “list” or “createvm” or “startvm”. All the
subcommands that VBoxManage supports are described in detail in chapter 8, VBoxManage, page
113.
Second, most of these subcommands require that you specify a particular virtual machine after
the subcommand. There are two ways you can do this:
• You can specify the VM name, as it is shown in the VirtualBox GUI. Note that if that name
contains spaces, then you must enclose the entire name in double quotes (as it is always
required with command line arguments that contain spaces).
For example:
VBoxManage startvm "Windows XP"

• You can specify the UUID, which is the internal unique identifier that VirtualBox uses to
refer to the virtual machine. Assuming that the aforementioned VM called “Windows XP”
has the UUID shown below, the following command has the same effect as the previous:
VBoxManage startvm 670e746d-abea-4ba6-ad02-2a3b043810a5

You can type VBoxManage list vms to have all currently registered VMs listed with all their
settings, including their respective names and UUIDs.
Some typical examples of how to control VirtualBox from the command line are listed below:
• To create a new virtual machine from the command line and immediately register it with
VirtualBox, use VBoxManage createvm with the --register option,1 like this:
$ VBoxManage createvm --name "SUSE 10.2" --register
VirtualBox Command Line Management Interface Version 4.3.18
(C) 2005-2014 Oracle Corporation
All rights reserved.
Virtual machine ’SUSE 10.2’ is created.
UUID: c89fc351-8ec6-4f02-a048-57f4d25288e5
Settings file: ’/home/username/.config/VirtualBox/Machines/SUSE 10.2/SUSE 10.2.xml’
1 For

details, see chapter 8.7, VBoxManage createvm, page 125.

113

8 VBoxManage
As can be seen from the above output, a new virtual machine has been created with a new
UUID and a new XML settings file.
• To show the configuration of a particular VM, use VBoxManage showvminfo; see chapter
8.5, VBoxManage showvminfo, page 123 for details and an example.
• To change settings while a VM is powered off, use VBoxManage modifyvm, e.g. as follows:
VBoxManage modifyvm "Windows XP" --memory "512MB"

For details, see chapter 8.8, VBoxManage modifyvm, page 125.
• To change the storage configuration (e.g. to add a storage controller and then a virtual
disk), use VBoxManage storagectl and VBoxManage storageattach; see chapter 8.19,
VBoxManage storagectl, page 139 and chapter 8.18, VBoxManage storageattach, page 137
for details.
• To control VM operation, use one of the following:
– To start a VM that is currently powered off, use VBoxManage startvm; see chapter
8.12, VBoxManage startvm, page 134 for details.
– To pause or save a VM that is currently running or change some of its settings, use
VBoxManage controlvm; see chapter 8.13, VBoxManage controlvm, page 134 for details.

8.2 Commands overview
When running VBoxManage without parameters or when supplying an invalid command line, the
below syntax diagram will be shown. Note that the output will be slightly different depending on
the host platform; when in doubt, check the output of VBoxManage for the commands available
on your particular host.
Usage:
VBoxManage []

General Options:
[-v|--version]
[-q|--nologo]
[--settingspw ]
[--settingspwfile ]

print version number and exit
suppress the logo
provide the settings password
provide a file containing the settings password

Commands:
list [--long|-l]

showvminfo
showvminfo

[--details]
[--machinereadable]
--log

registervm

unregistervm

[--delete]

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8 VBoxManage
createvm

--name
[--groups , ...]
[--ostype ]
[--register]
[--basefolder ]
[--uuid ]

modifyvm

115

116

8 VBoxManage
[--uuid ]
[--register]
import

[--dry-run|-n]
[--options keepallmacs|keepnatmacs]
[more options]
(run with -n to have options displayed
for a particular OVF)

export

startvm

...
[--type gui|sdl|headless]

controlvm

[--allowlocallogon ] |
teleport --host --port
[--maxdowntime ]
[--passwordfile |
--password ] |
plugcpu |

117

8 VBoxManage
unplugcpu |
cpuexecutioncap <1-100>
webcam | |
discardstate

adoptstate

snapshot

closemedium

disk|dvd|floppy
[--delete]

storageattach

storagectl

bandwidthctl

add --type disk|network
--limit [k|m|g|K|M|G] |
set
--limit [k|m|g|K|M|G] |
remove |
list [--machinereadable]

118

8 VBoxManage
(limit units: k=kilobit, m=megabit, g=gigabit,
K=kilobyte, M=megabyte, G=gigabyte)
showhdinfo

createhd

--filename
[--size |--sizebyte ]
[--diffparent |
[--format VDI|VMDK|VHD] (default: VDI)
[--variant Standard,Fixed,Split2G,Stream,ESX]

modifyhd

clonehd

[--format VDI|VMDK|VHD|RAW|]
[--variant Standard,Fixed,Split2G,Stream,ESX]
[--existing]

convertfromraw

[--format VDI|VMDK|VHD]
[--variant Standard,Fixed,Split2G,Stream,ESX]
[--uuid ]
stdin
[--format VDI|VMDK|VHD]
[--variant Standard,Fixed,Split2G,Stream,ESX]
[--uuid ]

convertfromraw

getextradata

global|
|enumerate

setextradata

global|

[] (no value deletes key)

setproperty

usbfilter

add
--target |global
--name
--action ignore|hold (global filters only)
[--active yes|no] (yes)
[--vendorid ] (null)
[--productid ] (null)
[--revision ] (null)
[--manufacturer ] (null)
[--product ] (null)
[--remote yes|no] (null, VM filters only)
[--serialnumber ] (null)
[--maskedinterfaces ]

usbfilter

modify
--target |global
[--name ]
[--action ignore|hold] (global filters only)

119

remove
--target |global

sharedfolder

add
--name --hostpath
[--transient] [--readonly] [--automount]

sharedfolder

remove
--name [--transient]

guestcontrol

exec[ute]
--image --username
[--passwordfile | --password ]
[--domain ] [--verbose] [--timeout ]
[--environment "= [=]"]
[--wait-exit] [--wait-stdout] [--wait-stderr]
[--dos2unix] [--unix2dos]
[-- [] ... []]
copyfrom
--username
[--passwordfile | --password ]
[--domain ] [--verbose]
[--dryrun] [--follow] [--recursive]
copyto|cp
--username
[--passwordfile | --password ]
[--domain ] [--verbose]
[--dryrun] [--follow] [--recursive]
createdir[ectory]|mkdir|md
... --username
[--passwordfile | --password ]
[--domain ] [--verbose]
[--parents] [--mode ]
removedir[ectory]|rmdir
... --username
[--passwordfile | --password ]
[--domain ] [--verbose]
[--recursive|-R|-r]
removefile|rm
... --username
[--passwordfile | --password ]
[--domain ] [--verbose]
ren[ame]|mv
... --username
[--passwordfile | --password ]
[--domain ] [--verbose]
createtemp[orary]|mktemp

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