Virtualization Getting Started Guide Red Hat Enterprise Linux 6 Dayle Parker
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Red Hat Enterprise Linux 6 Virtualization Getting Started Guide An introduction to virtualization concepts Dayle Parker Scott Radvan Laura Novich Jacquelynn East Red Hat Enterprise Linux 6 Virtualization Getting Started Guide An introduction to virtualization concepts Dayle Parker Red Hat Engineering Co ntent Services email@example.com m Laura No vich Red Hat Engineering Co ntent Services lno firstname.lastname@example.org m Jacquelynn East Red Hat Engineering Co ntent Services email@example.com m Sco tt Radvan Red Hat Engineering Co ntent Services firstname.lastname@example.org m Legal Notice Co pyright © 20 11-20 15 Red Hat, Inc. This do cument is licensed by Red Hat under the Creative Co mmo ns Attributio n-ShareAlike 3.0 Unpo rted License. If yo u distribute this do cument, o r a mo dified versio n o f it, yo u must pro vide attributio n to Red Hat, Inc. and pro vide a link to the o riginal. If the do cument is mo dified, all Red Hat trademarks must be remo ved. Red Hat, as the licenso r o f this do cument, waives the right to enfo rce, and agrees no t to assert, Sectio n 4 d o f CC-BY-SA to the fullest extent permitted by applicable law. Red Hat, Red Hat Enterprise Linux, the Shado wman lo go , JBo ss, MetaMatrix, Fedo ra, the Infinity Lo go , and RHCE are trademarks o f Red Hat, Inc., registered in the United States and o ther co untries. Linux ® is the registered trademark o f Linus To rvalds in the United States and o ther co untries. Java ® is a registered trademark o f Oracle and/o r its affiliates. XFS ® is a trademark o f Silico n Graphics Internatio nal Co rp. o r its subsidiaries in the United States and/o r o ther co untries. MySQL ® is a registered trademark o f MySQL AB in the United States, the Euro pean Unio n and o ther co untries. No de.js ® is an o fficial trademark o f Jo yent. Red Hat So ftware Co llectio ns is no t fo rmally related to o r endo rsed by the o fficial Jo yent No de.js o pen so urce o r co mmercial pro ject. The OpenStack ® Wo rd Mark and OpenStack Lo go are either registered trademarks/service marks o r trademarks/service marks o f the OpenStack Fo undatio n, in the United States and o ther co untries and are used with the OpenStack Fo undatio n's permissio n. We are no t affiliated with, endo rsed o r spo nso red by the OpenStack Fo undatio n, o r the OpenStack co mmunity. All o ther trademarks are the pro perty o f their respective o wners. Abstract The Red Hat Enterprise Linux Virtualizatio n Getting Started Guide describes the basics o f virtualizatio n and the virtualizatio n pro ducts and techno lo gies that are available with Red Hat Enterprise Linux. T able of Cont ent s T able of Contents . .hapt C . . . .er . .1. .. Int . . .roduct . . . . . .ion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2. . . . . . . . . . 1.1. Who s ho uld read this g uid e? 2 1.2. Virtualiz atio n in Red Hat Enterp ris e Linux 6 2 1.3. Red Hat Enterp ris e Virtualiz atio n (RHEV) 2 1.4. Do c umentatio n s uite 2 . .hapt C . . . .er . .2. .. What . . . . . is . . virt . . . ualiz . . . . at . . ion . . . and . . . . migrat . . . . . .ion? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5. . . . . . . . . . 2 .1. What is virtualiz atio n? 5 2 .2. Mig ratio n 5 2 .2.1. Benefits o f mig rating virtual mac hines 6 2 .3. Virtualiz ed to virtualiz ed mig ratio n (V2V) 6 . .hapt C . . . .er . .3. . .Advant . . . . . . ages . . . . .and . . . .misconcept . . . . . . . . . . ions . . . . of . . .virt . . .ualiz . . . .at . .ion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8. . . . . . . . . . 3 .1. Virtualiz atio n c o s ts 8 3 .2. Virtualiz atio n learning c urve 8 3 .3. Perfo rmanc e 8 3 .4. Dis as ter rec o very 9 3 .5. Sec urity .5.1. Virtualiz atio n s ec urity features 3 3 .6 . Virtualiz atio n fo r s ervers and ind ivid uals 3 .6 .1. Virtualiz atio n d ep lo yment s c enario s 9 9 10 10 . .hapt C . . . .er . .4. .. Int . . .roduct . . . . . .ion . . .t.o. Red . . . . Hat . . . . virt . . . ualiz . . . . at . . ion . . . product . . . . . . . .s. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1. 2. . . . . . . . . . 4 .1. KVM and virtualiz atio n in Red Hat Enterp ris e Linux 12 4 .2. lib virt and lib virt to o ls 14 4 .3. Virtualiz ed hard ware d evic es 4 .3.1. Virtualiz ed and emulated d evic es 4 .3.2. Para-virtualiz ed d evic es 4 .3.3. Phys ic al ho s t d evic es 4 .4. G ues t CPU mo d els 4 .5. Sto rag e 15 15 17 19 20 20 4 .5.1. Sto rag e p o o ls 4 .5.2. Sto rag e vo lumes 21 21 4 .5.3. Emulated s to rag e d evic es 4 .5.4. Ho s t s to rag e 21 22 . .hapt C . . . .er . .5. . .Virt . . . ualiz . . . . at . . ion ...T . .ools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2. 4. . . . . . . . . . 5 .1. virs h 24 5 .2. virt-manag er 24 5 .3. virt-ins tall 5 .4. g ues tfis h 5 .5. O ther us eful to o ls 24 25 25 . .ppendix A . . . . . . . A. . . Revision . . . . . . . . .Hist . . . ory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2. 9. . . . . . . . . . 1 Virt ualiz at ion G et t ing St art ed G uide Chapter 1. Introduction The Virtualization Getting Started Guide introduces the basics of virtualization and assists with the navigation of other virtualization documentation and products that Red Hat provides. This guide also explains the advantages of virtualization and dispels some common myths that exist regarding virtualization. 1.1. Who should read t his guide? This guide is designed for anyone wishing to understand the basics of virtualization, but may be of particular interest to: Those who are new to virtualization and seeking knowledge about the benefits offered. Those considering deployment of virtualized machines in their environment. Those looking for an overview of the virtualization technologies that Red Hat produces and supports. 1.2. Virt ualiz at ion in Red Hat Ent erprise Linux 6 Red Hat Enterprise Linux contains packages and tools to support a variety of virtualized environments. Virtualization in Red Hat Enterprise Linux 6 is carried out by KVM (Kernel-based Virtual Machine). KVM is a full virtualization solution built into Red Hat Enterprise Linux 6. Refer to Chapter 4, Introduction to Red Hat virtualization products for more about the virtualization products available in Red Hat Enterprise Linux 6. 1.3. Red Hat Ent erprise Virt ualiz at ion (RHEV) Red Hat Enterprise Virtualization (RHEV) is a complete enterprise virtualization management solution for server and desktop virtualization, based on Kernel-based Virtual Machine (KVM) technology. D esigned for enterprise-class scalability and performance, Red Hat Enterprise Virtualization enables management of your entire virtual infrastructure, including hosts, virtual machines, networks, storage, and users from a centralized graphical interface. Red Hat Enterprise Virtualization includes the RHEV Manager infrastructure management system and the RHEV Hypervisor, which supports a wide range of Windows and Linux server and desktop operating systems — all while delivering reliability, stability, and the lowest total cost of ownership in its class. D ownload a fully supported 60-day evaluation version of Red Hat Enterprise Virtualization from http://www.redhat.com/en/technologies/virtualization/enterprise-virtualization. 1.4 . Document at ion suit e Red Hat offers a wealth of documentation solutions across its various virtualization products. Coverage of Red Hat Enterprise Linux and its inbuilt virtualization products includes: 2 Chapt er 1 . Int roduct ion Red Hat Enterprise Linux — Virtualization Getting Started Guide: This guide provides an introduction to virtualization concepts, advantages, and tools, and an overview of Red Hat virtualization documentation and products. Red Hat Enterprise Linux — Virtualization Host Configuration and Guest Installation Guide: This guide covers the installation of virtualization software and configuration of guest machines on a virtualization host. Red Hat Enterprise Linux — Virtualization Administration Guide: This guide covers administration of hosts, networking, storage, and device and guest management using either virt-manager or virsh as primary configuration tools. This guide also includes a libvirt and QEMU reference, as well as troubleshooting information. Red Hat Enterprise Linux — Virtualization Security Guide: This guide provides an overview of virtualization security technologies provided by Red Hat. Also included are recommendations for securing hosts, guests, and shared infrastructure and resources in virtualized environments. Red Hat Enterprise Linux — Virtualization Tuning and Optimization Guide: This guide provides tips, tricks and suggestions for making full use of virtualization performance features and options for your systems and guest virtual machines. Red Hat Enterprise Linux — V2V Guide: This guide describes importing virtual machines from KVM, Xen and VMware ESX/ESX(i) hypervisors to Red Hat Enterprise Virtualization and KVM managed by libvirt. The Red Hat Enterprise Virtualization documentation suite provides information on installation, development of applications, configuration and usage of the Red Hat Enterprise Virtualization platform and its related products. Red Hat Enterprise Virtualization — Installation Guide: This guide describes how to prepare for and set up a Red Hat Enterprise Virtualization environment, and how to upgrade a Red Hat Enterprise Virtualization environment to the latest release. It also outlines how to set up hypervisors and perform initial configuration of a Red Hat Enterprise Virtualization environment. Red Hat Enterprise Virtualization — Administration Guide: This guide describes how to configure and administer a Red Hat Enterprise Virtualization environment after that environment has been set up for the first time, including how to add hypervisors, storage domains, and external providers to the environment, how to manage resources such as virtual machines, virtual disks, and templates, and how to take and restore backups. Red Hat Enterprise Virtualization — User Guide: This guide describes how to use the User Portal of a Red Hat Enterprise Virtualization environment, including the functionality provided by the Basic and Extended tabs, how to create and work with virtual machines and templates, and how to monitor resource usage. Red Hat Enterprise Virtualization — Technical Guide: This guide describes how to use the REST API, the Python and Java software development kits, and command-line tools specific to Red Hat Enterprise Virtualization. It also outlines the underlying technical concepts behind Red Hat Enterprise Virtualization. Red Hat Enterprise Virtualization — Manager Release Notes: This guide contains information on the Red Hat Enterprise Virtualization Manager specific to the current release. Red Hat Enterprise Virtualization — Technical Notes: This guide describes the changes that have been made between the current release and the previous release. 3 Virt ualiz at ion G et t ing St art ed G uide Note All of the guides for these products are available at the Red Hat Customer Portal: https://access.redhat.com/documentation/en-US/ 4 Chapt er 2 . What is virt ualiz at ion and migrat ion? Chapter 2. What is virtualization and migration? This chapter discusses terms related to virtualization and migration. 2.1. What is virt ualiz at ion? Virtualization is a broad computing term used for running software, usually multiple operating systems, concurrently and in isolation from other programs on a single system. Most existing implementations of virtualization use a hypervisor, a software layer or subsystem that controls hardware and provides guest operating systems with access to underlying hardware. The hypervisor allows multiple operating systems, called guests, to run on the same physical system by offering virtualized hardware to the guest operating system. There are various methods for virtualizing operating systems: Fu ll virt u aliz at io n Full virtualization uses the hardware features of the processor to provide guests with total abstraction of the underlying physical system. This creates a new virtual system, called a virtual machine, that allows guest operating systems to run without modifications. The guest operating system and any applications on the guest virtual machine are unaware of their virtualized environment and run normally. Hardware-assisted virtualization is the technique used for full virtualization with KVM (Kernel-based Virtual Machine) in Red Hat Enterprise Linux. Para- virt u aliz at io n Para-virtualization employs a collection of software and data structures that are presented to the virtualized guest, requiring software modifications in the guest to use the paravirtualized environment. Para-virtualization can encompass the entire kernel, as is the case for Xen para-virtualized guests, or drivers that virtualize I/O devices. So f t ware virt u aliz at io n ( o r emu lat io n ) Software virtualization uses slower binary translation and other emulation techniques to run unmodified operating systems. Software virtualization is unsupported by Red Hat Enterprise Linux. Note For more information and detailed instructions on guest installation, refer to the Red Hat Enterprise Linux 6 Virtualization Host Configuration and Guest Installation Guide. 2.2. Migrat ion Migration describes the process of moving a guest virtual machine from one host to another. This is possible because the virtual machines are running in a virtualized environment instead of directly on the hardware. There are two ways to migrate a virtual machine: live and offline. Mig rat io n T yp es O f f lin e mig rat io n 5 Virt ualiz at ion G et t ing St art ed G uide An offline migration suspends the guest virtual machine, and then moves an image of the virtual machine's memory to the destination host. The virtual machine is then resumed on the destination host and the memory used by the virtual machine on the source host is freed. Live mig rat io n Live migration is the process of migrating an active virtual machine from one physical host to another. 2.2.1. Benefit s of migrat ing virt ual machines Migration is useful for: Lo ad b alan cin g When a host machine is overloaded, one or many of its virtual machines could be migrated to other hosts using live migration. U p g rad in g o r makin g ch an g es t o t h e h o st When the need arises to upgrade, add, or remove hardware devices on one host, virtual machines can be safely relocated to other hosts. This means that guests do not experience any downtime due to changes that are made to any of the hosts. En erg y savin g Virtual machines can be redistributed to other hosts and the unloaded host systems can be powered off to save energy and cut costs in low usage periods. G eo g rap h ic mig rat io n Virtual machines can be moved to another physical location for lower latency or for other special circumstances. It is important to understand that the migration process moves the virtual machine's memory, and from Red Hat Enterprise Linux 6.3, the disk volume associated with the virtual machine is also migrated. This process is done using live block migration. Shared, networked storage can be used to store guest images to be migrated. When migrating virtual machines, it is recommended to use lib virt -managed storage pools for shared storage. Note For more information on migration, refer to the Red Hat Enterprise Linux 6 Virtualization Administration Guide. 2.3. Virt ualiz ed t o virt ualiz ed migrat ion (V2V) Red Hat Enterprise Linux 6 provides tools for converting virtual machines from other types of hypervisors to KVM. The vi rt-v2v tool converts and imports virtual machines from Xen, other versions of KVM, VMware ESX, and Hyper-V. From Red Hat Enterprise Linux 6.5, the vi rt-v2v tool converts and imports virtual machines with virtual disk image formats including VHD X, VMD K, OVF, raw, and qcow2. 6 Chapt er 2 . What is virt ualiz at ion and migrat ion? Note For more information on V2V, refer to the Red Hat Enterprise Linux 6 V2V Guide. 7 Virt ualiz at ion G et t ing St art ed G uide Chapter 3. Advantages and misconceptions of virtualization There are many advantages to virtualization and perhaps an equal amount of misconceptions surrounding it. This chapter explores these points. 3.1. Virt ualiz at ion cost s A common misconception is that virtualization is too expensive to justify the change. Virtualization can be expensive to introduce but often it saves money in the long term. It is important to perform a Return on Investment (ROI) analysis to determine the best use of virtualization in your environment. Consider the following benefits: Less p o wer Using virtualization negates much of the need for multiple physical platforms. This equates to less power being drawn for machine operation and cooling, resulting in reduced energy costs. The initial cost of purchasing multiple physical platforms, combined with the machines' power consumption and required cooling, is drastically cut by using virtualization. Less main t en an ce Provided adequate planning is performed before migrating physical systems to virtualized ones, less time is spent maintaining them. This means less money being spent on parts and labor. Ext en d ed lif e f o r in st alled so f t ware Older versions of software may not run on newer, bare metal machines directly. However, by running the older software virtually on a larger, faster system, the life of the software may be extended while taking advantage of the performance from the newer system. Pred ict ab le co st s A Red Hat Enterprise Linux subscription provides support for virtualization at a fixed rate, making it easy to predict costs. Less sp ace Consolidating servers onto fewer machines means less physical space is required. This means the space normally occupied by server hardware can be used for other purposes. 3.2. Virt ualiz at ion learning curve A misconception exists that virtualization is difficult to learn. In truth, virtualization is no more difficult or easy to learn than any new process. The skills required for managing and supporting a physical environment are easily transferable to a virtual one. Virtual environments function similarly to their physical counterparts, ensuring the learning curve remains a slight one. 3.3. Performance On older virtualization versions that supported only a single CPU, virtual machines experienced noticeable performance limitations. This created a long-lasting misconception that virtualization solutions are slow. 8 Chapt er 3. Advant ages and misconcept ions of virt ualiz at ion This is no longer the case; modern virtualization technology has greatly improved the speed of virtual machines. Benchmarks show that virtual machines can run typical server applications nearly as efficiently as bare metal systems: Red Hat Enterprise Linux 6.4 and KVM recorded an industry-leading TPC-C benchmark with an IBM D B2 database running in an entirely virtualized x86 environment and delivering 88% of bare metal performance. D ue to resource demands, databases have previously been reserved for baremetal deployments only, and represent one of the last strongholds within a datacenter to be virtualized. The industry standard SAP Sales and D istribution (SD ) Standard Application Benchmark found Red Hat Enterprise Linux 6.2 and KVM to demonstrate a virtualization efficiency of 85% when comparing a bare metal system running on identical hardware. Red Hat Enterprise Linux 6.1 and KVM achieved record-setting virtualization performance in the SPECvirt_sc2010 benchmark recorded by the Standard Performance Evaluation Corporation (SPEC), setting the best virtual performance mark of any published SPECvirt result. The SPECvirt_sc2010 metric measures the end-to-end performance of system components in virtualized data center servers. Note For more details on these virtualization benchmarks, visit: Red Hat and IBM Achieve Leading Performance Benchmark Results at http://www.redhat.com/about/news/archive/2013/2/red-hat-and-ibm-achieve-leadingperformance-benchmark-results Red Hat Knowledgebase, SAP-SD Benchmark running in a VM – Leadership Performance using RHEL 6 / KVM at https://access.redhat.com/knowledge/articles/216943 The Standard Performance Evaluation Corporation (SPEC) at http://www.spec.org Red Hat Achieves New Top Virtualization Performance Benchmark with HP at http://investors.redhat.com/releasedetail.cfm?ReleaseID =617594 For more information on performance tuning for virtualization, refer to the Red Hat Enterprise Linux 6 Virtualization Tuning and Optimization Guide. 3.4 . Disast er recovery D isaster recovery is quicker and easier when the systems are virtualized. On a physical system, if something serious goes wrong, a complete re-install of the operating system is usually required, resulting in hours of recovery time. However, if the systems are virtualized this is much faster due to migration ability. If the requirements for live migration are followed, virtual machines can be restarted on another host, and the longest possible delay would be in restoring guest data. Also, because each of the virtualized systems are completely separate to each other, one system's downtime will not affect any others. 3.5. Securit y A virtual machine uses SELinux and sVirt to improve security in virtualization. This section includes an overview of the security options available. 3.5.1. Virt ualiz at ion securit y feat ures 9 Virt ualiz at ion G et t ing St art ed G uide SELin u x SELinux was developed by the US National Security Agency and others to provide Mandatory Access Control (MAC) for Linux. Under control of SELinux, all processes and files are given what is known as a type, and access is limited by fine-grained controls. SELinux limits the abilities of an attacker and works to prevent many common security exploits such as buffer overflow attacks and privilege escalation. SELinux strengthens the security model of Red Hat Enterprise Linux hosts and virtualized Red Hat Enterprise Linux guests. SELinux is configured and tested to work, by default, with all virtualization tools shipped with Red Hat Enterprise Linux 6. sVirt sVirt is a technology included in Red Hat Enterprise Linux 6 that integrates SELinux and virtualization. It applies Mandatory Access Control (MAC) to improve security when using virtual machines, and improves security and hardens the system against bugs in the hypervisor that might be used as an attack vector for the host or to another virtual machine. Note For more information on security for virtualization, refer to the Red Hat Enterprise Linux 6 Virtualization Security Guide. 3.6. Virt ualiz at ion for servers and individuals Virtualization is not just for servers; it can be useful for individuals as well. D esktop virtualization offers centralized management, an improved desktop solution, and better disaster recovery. By using connection software, it is possible to connect to a desktop remotely. For servers, virtualization is not only for larger networks, but for any situation with two or more servers. It provides live migration, high availability, fault tolerance, and streamlined backups. 3.6.1. Virt ualiz at ion deployment scenarios These are examples of common deployment scenarios for virtualization, and the tools that can be used to deploy these scenarios. Small d ep lo ymen t s o f u p t o 3 p h ysical h o st s an d 10 g u est s: virt - man ag er A tool such as virt-manager can be useful to a small business running several servers that do not have strict uptime requirements or service-level agreements (SLAs). In this environment, a single administrator may be responsible for the entire infrastructure, and maintaining procedural flexibility is important if a component needs to be changed. This environment may contain applications such as web servers, file and print servers, and application servers. Larg e d ep lo ymen t s o r missio n - crit ical ap p licat io n s: R ed H at En t erp rise Virt u aliz at io n ( R H EV) A full virtualization platform such as Red Hat Enterprise Virtualization (RHEV) might suit an enterprise running larger deployments or mission-critical applications. In this environment, the physical infrastructure is large enough to require an IT department and the business requirements demand a defined response to new needs. Some examples of a large 10 Chapt er 3. Advant ages and misconcept ions of virt ualiz at ion deployment suited to Red Hat Enterprise Virtualization may include databases, trading platforms, or messaging systems that must run continuously without any downtime. So f t ware d evelo p ers p ro d u cin g man ag emen t ap p licat io n s: lib virt Both virt-manager and Red Hat Enterprise Virtualization (RHEV) use libvirt to manage virtual machines. libvirt is a virtualization application programming interface (API) that allows software developers to produce and adapt management applications. 11 Virt ualiz at ion G et t ing St art ed G uide Chapter 4. Introduction to Red Hat virtualization products This chapter introduces the various virtualization products available in Red Hat Enterprise Linux. 4 .1. KVM and virt ualiz at ion in Red Hat Ent erprise Linux Wh at is K VM? KVM (Kernel-based Virtual Machine) is a full virtualization solution for Linux on AMD 64 and Intel 64 hardware that is built into the standard Red Hat Enterprise Linux 6 kernel. It can run multiple, unmodified Windows and Linux guest operating systems. The KVM hypervisor in Red Hat Enterprise Linux is managed with the lib virt API and tools built for lib virt (such as vi rt-manag er and vi rsh). Virtual machines are executed and run as multi-threaded Linux processes controlled by these tools. O verco mmit t in g The KVM hypervisor supports overcommitting of system resources. Overcommitting means allocating more virtualized CPUs or memory than the available resources on the system. Memory overcommitting allows hosts to utilize memory and virtual memory to increase guest densities. Important Overcommitting involves possible risks to system stability. For more information on overcommitting with KVM, and the precautions that should be taken, refer to the Red Hat Enterprise Linux 6 Virtualization Administration Guide. T h in p ro visio n in g Thin provisioning allows the allocation of flexible storage and optimizes the available space for every guest virtual machine. It gives the appearance that there is more physical storage on the guest than is actually available. This is not the same as overcommitting as this only pertains to storage and not CPUs or memory allocations. However, like overcommitting, the same warning applies. Important Thin provisioning involves possible risks to system stability. For more information on thin provisioning with KVM, and the precautions that should be taken, refer to the Red Hat Enterprise Linux 6 Virtualization Administration Guide. K SM Kernel Same-page Merging (KSM), used by the KVM hypervisor, allows KVM guests to share identical memory pages. These shared pages are usually common libraries or other identical, high-use data. KSM allows for greater guest density of identical or similar guest operating systems by avoiding memory duplication. 12 Chapt er 4 . Int roduct ion t o Red Hat virt ualiz at ion product s Note For more information on KSM, refer to the Red Hat Enterprise Linux 6 Virtualization Administration Guide. Q EMU G u est Ag en t The QEMU Guest Agent runs on the guest operating system and allows the host machine to issue commands to the guest operating system. Note For more information on the QEMU Guest Agent, refer to the Red Hat Enterprise Linux 6 Virtualization Host Configuration and Guest Installation Guide. H yp er- V En lig h t en men t KVM in Red Hat Enterprise Linux 6.5 implements several Hyper-V compatible functions that are used by Windows guests to improve performance and stability, allowing Windows guests to perform as if they were running on a Microsoft Hyper-V hypervisor. Note For more information on Hyper-V Enlightenment, refer to the Red Hat Enterprise Linux 6 Virtualization Host Configuration and Guest Installation Guide. D isk I/O t h ro t t lin g When several virtual machines are running simultaneously, they can interfere with system performance by using excessive disk I/O. D isk I/O throttling in KVM provides the ability to set a limit on disk I/O requests sent from virtual machines to the host machine. This can prevent a virtual machine from over utilizing shared resources, and impacting the performance of other virtual machines. Note For instructions on using disk I/O throttling, refer to the Red Hat Enterprise Linux 6 Virtualization Tuning and Optimization Guide. K VM g u est virt u al mach in e co mp at ib ilit y To verify whether your processor supports the virtualization extensions and for information on enabling the virtualization extensions if they are disabled, refer to the Red Hat Enterprise Linux 6 Virtualization Administration Guide. Red Hat Enterprise Linux 6 servers have certain support limits. The following URLs explain the processor and memory amount limitations for Red Hat Enterprise Linux: 13 Virt ualiz at ion G et t ing St art ed G uide For host systems: https://access.redhat.com/site/articles/rhel-limits For the KVM hypervisor: https://access.redhat.com/site/articles/rhel-kvm-limits For a complete chart of supported operating systems and host and guest combinations refer to https://access.redhat.com/site/supported-hypervisors. 4 .2. libvirt and libvirt t ools The libvirt package is a hypervisor-independent virtualization API that is able to interact with the virtualization capabilities of a range of operating systems. The libvirt package provides: A common, generic, and stable layer to securely manage virtual machines on a host. A common interface for managing local systems and networked hosts. All of the APIs required to provision, create, modify, monitor, control, migrate, and stop virtual machines, but only if the hypervisor supports these operations. Although multiple hosts may be accessed with lib virt simultaneously, the APIs are limited to single node operations. lib virt focuses on managing single hosts and provides APIs to enumerate, monitor and use the resources available on the managed node, including CPUs, memory, storage, networking and NonUniform Memory Access (NUMA) partitions. The management tools can be located on separate physical machines from the host using secure protocols. Red Hat Enterprise Linux 6 supports lib virt and includes lib virt -based tools as its default method for virtualization management (as in Red Hat Enterprise Virtualization Management). The libvirt package is available as free software under the GNU Lesser General Public License. The libvirt project aims to provide a long term stable C API to virtualization management tools, running on top of varying hypervisor technologies. The libvirt package supports Xen on Red Hat Enterprise Linux 5, and it supports KVM on both Red Hat Enterprise Linux 5 and Red Hat Enterprise Linux 6. virsh The vi rsh command-line tool is built on the lib virt management API and operates as an alternative to the graphical vi rt-manag er application. The vi rsh command can be used in read-only mode by unprivileged users or, with root access, full administration functionality. The vi rsh command is ideal for scripting virtualization administration. virt - man ag er vi rt-manag er is a graphical desktop tool for managing virtual machines. It allows access to graphical guest consoles and can be used to perform virtualization administration, virtual machine creation, migration, and configuration tasks. The ability to view virtual machines, host statistics, device information and performance graphs is also provided. The local hypervisor and remote hypervisors can be managed through a single interface. Note For more information on vi rsh and virt - man ag er, refer to the Red Hat Enterprise Linux 6 Virtualization Administration Guide. 14 Chapt er 4 . Int roduct ion t o Red Hat virt ualiz at ion product s Note Some virtualization commands in Red Hat Enterprise Linux 6 allow you to specify a remote libvirt connection. For example: virt-df -c qemu://remote/system -d Guest However, libguestfs in Red Hat Enterprise Linux 6 cannot access remote guests, and commands using remote URLs like this do not work as expected. This affects the following Red Hat Enterprise Linux 6 commands: guestfish guestmount virt-alignment-scan virt-cat virt-copy-in virt-copy-out virt-df virt-edit virt-filesystems virt-inspector virt-inspector2 virt-list-filesystems virt-list-partitions virt-ls virt-rescue virt-sysprep virt-tar virt-tar-in virt-tar-out virt-win-reg 4 .3. Virt ualiz ed hardware devices Virtualization on Red Hat Enterprise Linux 6 presents three distinct types of system devices to virtual machines. The three types include: Virtualized and emulated devices Para-virtualized devices Physically shared devices These hardware devices all appear as being physically attached to the virtual machine but the device drivers work in different ways. 4 .3.1. Virt ualiz ed and emulat ed devices KVM implements many core devices for virtual machines in software. These emulated hardware devices are crucial for virtualizing operating systems. Emulated devices are virtual devices which exist entirely in software. 15 Virt ualiz at ion G et t ing St art ed G uide Emulated drivers may use either a physical device or a virtual software device. Emulated drivers are a translation layer between the virtual machine and the Linux kernel (which manages the source device). The device level instructions are completely translated by the KVM hypervisor. Any device, of the same type (storage, network, keyboard, and mouse) and recognized by the Linux kernel, may be used as the backing source device for the emulated drivers. Virt u al C PU s ( vC PU s) A host system can have up to 160 virtual CPUs (vCPUs) that can be presented to guests for their use, regardless of the number of host CPUs. Emu lat ed g rap h ics d evices Two emulated graphics devices are provided. These devices can be connected to with the SPICE (Simple Protocol for Independent Computing Environments) protocol or with VNC: A Cirrus CLGD 5446 PCI VGA card (using the cirrus device) A standard VGA graphics card with Bochs VESA extensions (hardware level, including all non-standard modes) Emu lat ed syst em co mp o n en t s The following core system components are emulated to provide basic system functions: Intel i440FX host PCI bridge PIIX3 PCI to ISA bridge PS/2 mouse and keyboard EvTouch USB Graphics Tablet PCI UHCI USB controller and a virtualized USB hub Emulated serial ports EHCI controller, virtualized USB storage and a USB mouse Emu lat ed so u n d d evices Red Hat Enterprise Linux 6.1 and above provides an emulated (Intel) HD A sound device, i ntel -hd a. This device is supported on the following guest operating systems: Red Hat Enterprise Linux 6, for i386 and x86_64 architectures Red Hat Enterprise Linux 5, for i386 and x86_64 architectures Red Hat Enterprise Linux 4, for i386 and x86_64 architectures Windows 7, for i386 and x86_64 architectures Windows 2008 R2, for the x86_64 architecture The following two emulated sound devices are also available, but are not recommended due to compatibility issues with certain guest operating systems: ac9 7, an emulated Intel 82801AA AC97 Audio compatible sound card es1370 , an emulated ENSONIQ AudioPCI ES1370 sound card Emu lat ed wat ch d o g d evices 16 Chapt er 4 . Int roduct ion t o Red Hat virt ualiz at ion product s Red Hat Enterprise Linux 6 provides two emulated watchdog devices. A watchdog can be used to automatically reboot a virtual machine when it becomes overloaded or unresponsive. The watchdog package must be installed on the guest. The two devices available are: i 6 30 0 esb, an emulated Intel 6300 ESB PCI watchdog device. It is supported in guest operating system Red Hat Enterprise Linux versions 6.0 and above, and is the recommended device to use. i b70 0 , an emulated iBase 700 ISA watchdog device. The i b70 0 watchdog device is only supported in guests using Red Hat Enterprise Linux 6.2 and above. Both watchdog devices are supported in i386 and x86_64 architectures for guest operating systems Red Hat Enterprise Linux 6.2 and above. Emu lat ed n et wo rk d evices There are two emulated network devices available: The e10 0 0 device emulates an Intel E1000 network adapter (Intel 82540EM, 82573L, 82544GC). The rtl 8139 device emulates a Realtek 8139 network adapter. Emu lat ed st o rag e d rivers Storage devices and storage pools can use these emulated devices to attach storage devices to virtual machines. The guest uses an emulated storage driver to access the storage pool. Note that like all virtual devices, the storage drivers are not storage devices. The drivers are used to attach a backing storage device, file or storage pool volume to a virtual machine. The backing storage device can be any supported type of storage device, file, or storage pool volume. T h e emu lat ed ID E d river KVM provides two emulated PCI ID E interfaces. An emulated ID E driver can be used to attach any combination of up to four virtualized ID E hard disks or virtualized ID E CD -ROM drives to each virtual machine. The emulated ID E driver is also used for virtualized CD -ROM and D VD -ROM drives. T h e emu lat ed f lo p p y d isk d rive d river The emulated floppy disk drive driver is used for creating virtualized floppy drives. 4 .3.2. Para-virt ualiz ed devices Para-virtualization provides a fast and efficient means of communication for guests to use devices on the host machine. KVM provides para-virtualized devices to virtual machines using the Virtio API as a layer between the hypervisor and guest. Some para-virtualized devices decrease I/O latency and increase I/O throughput to near bare-metal levels, while other para-virtualized devices add functionality to virtual machines that is not otherwise available. It is recommended to use para-virtualized devices instead of emulated devices for virtual machines running I/O intensive applications. 17 Virt ualiz at ion G et t ing St art ed G uide All virtio devices have two parts: the host device and the guest driver. Para-virtualized device drivers allow the guest operating system access to physical devices on the host system. The para-virtualized device drivers must be installed on the guest operating system. By default, the para-virtualized device drivers are included in Red Hat Enterprise Linux 4.7 and newer, Red Hat Enterprise Linux 5.4 and newer and Red Hat Enterprise Linux 6.0 and newer. The para-virtualized device drivers must be manually installed on Windows guests. Note For more information on using the para-virtualized devices and drivers, refer to the Red Hat Enterprise Linux 6 Virtualization Host Configuration and Guest Installation Guide. T h e p ara- virt u aliz ed n et wo rk d evice ( virt io - n et ) The para-virtualized network device is a virtual network device that provides network access to virtual machines with increased I/O performance and lower latency. T h e p ara- virt u aliz ed b lo ck d evice ( virt io - b lk) The para-virtualized block device is a high-performance virtual storage device with that provides storage to virtual machines with increased I/O performance and lower latency. The para-virtualized block device is supported by the hypervisor and is attached to the virtual machine (except for floppy disk drives, which must be emulated). T h e p ara- virt u aliz ed co n t ro ller d evice ( virt io - scsi) The para-virtualized SCSI controller device is a new feature in Red Hat Enterprise Linux 6.4 that provides a more flexible and scalable alternative to virtio-blk. A virtio-scsi guest is capable of inheriting the feature set of the target device, and can handle hundreds of devices compared to virtio-blk, which can only handle 28 devices. In Red Hat Enterprise Linux 6.4 and above, virtio-scsi is fully supported for the following guest operating systems: Red Hat Enterprise Linux 6.4 and above Windows Server 2008 Windows 7 Windows Server 2012 Windows 8 (32/64 bit) T h e p ara- virt u aliz ed clo ck Guests using the Time Stamp Counter (TSC) as a clock source may suffer timing issues. KVM works around hosts that do not have a constant Time Stamp Counter by providing guests with a para-virtualized clock. Additionally, the para-virtualized clock assists with time adjustments needed after a guest runs S3 or suspend to RAM operations. T h e p ara- virt u aliz ed serial d evice ( virt io - serial) The para-virtualized serial device is a bytestream-oriented, character stream device, and provides a simple communication interface between the host's user space and the guest's user space. 18 Chapt er 4 . Int roduct ion t o Red Hat virt ualiz at ion product s T h e b allo o n d evice ( virt io - b allo o n ) The balloon device can designate part of a virtual machine's RAM as not being used (a process known as balloon inflation), so that the memory can be freed for the host (or for other virtual machines on that host) to use. When the virtual machine needs the memory again, the balloon can be deflated and the host can distribute the RAM back to the virtual machine. T h e p ara- virt u aliz ed g rap h ics card ( Q XL) The para-virtualized graphics card works with the QXL driver to provide an efficient way to display a virtual machine's graphics from a remote host. The QXL driver is required to use SPICE. 4 .3.3. Physical host devices Certain hardware platforms allow virtual machines to directly access various hardware devices and components. This process in virtualization is known as device assignment. D evice assignment is also known as passthrough. PC I d evice assig n men t The KVM hypervisor supports attaching PCI devices on the host system to virtual machines. PCI device assignment allows guests to have exclusive access to PCI devices for a range of tasks. It allows PCI devices to appear and behave as if they were physically attached to the guest virtual machine. D evice assignment is supported on PCI Express devices, with the exception of graphics cards. Parallel PCI devices may be supported as assigned devices, but they have severe limitations due to security and system configuration conflicts. Note For more information on device assignment, refer to the Red Hat Enterprise Linux 6 Virtualization Host Configuration and Guest Installation Guide. U SB p asst h ro u g h The KVM hypervisor supports attaching USB devices on the host system to virtual machines. USB device assignment allows guests to have exclusive access to USB devices for a range of tasks. It allows USB devices to appear and behave as if they were physically attached to the virtual machine. Note For more information on USB passthrough, refer to the Red Hat Enterprise Linux 6 Virtualization Administration Guide. SR - IO V SR-IOV (Single Root I/O Virtualization) is a PCI Express standard that extends a single physical PCI function to share its PCI resources as separate, virtual functions (VFs). Each function is capable of being used by a different virtual machine via PCI device assignment. 19 Virt ualiz at ion G et t ing St art ed G uide An SR-IOV capable PCI-e device, provides a Single Root Function (for example, a single Ethernet port) and presents multiple, separate virtual devices as unique PCI device functions. Each virtual device may have its own unique PCI configuration space, memorymapped registers, and individual MSI-based interrupts. Note For more information on SR-IOV, refer to the Red Hat Enterprise Linux 6 Virtualization Host Configuration and Guest Installation Guide. N PIV N_Port ID Virtualization (NPIV) is a functionality available with some Fibre Channel devices. NPIV shares a single physical N_Port as multiple N_Port ID s. NPIV provides similar functionality for Fibre Channel Host Bus Adapters (HBAs) that SR-IOV provides for PCIe interfaces. With NPIV, virtual machines can be provided with a virtual Fibre Channel initiator to Storage Area Networks (SANs). NPIV can provide high density virtualized environments with enterprise-level storage solutions. Note For more information on NPIV, refer to the Red Hat Enterprise Linux 6 Virtualization Administration Guide. 4 .4 . Guest CPU models CPU models define which host CPU features are exposed to the guest operating system. q emu - kvm and lib virt contain definitions for several current processor models, allowing users to enable CPU features that are available only in newer CPU models. The set of CPU features that can be exposed to guests depends on support in the host CPU, the kernel, and q emu - kvm code. To allow safe migration of virtual machines between hosts with different sets of CPU features, q emu kvm does not expose all features from the host CPU to guest operating systems by default. Instead, CPU features are exposed based on the chosen CPU model. If a virtual machine has a given CPU feature enabled, it is not possible to migrate it to a host that does not support exposing that feature to guests. Note For more information on guest CPU models, refer to the Red Hat Enterprise Linux 6 Virtualization Host Configuration and Guest Installation Guide. 4 .5. St orage Storage for virtual machines is abstracted from the physical storage used by the virtual machine. It is attached to the virtual machine using the para-virtualized or emulated block device drivers. 20 Chapt er 4 . Int roduct ion t o Red Hat virt ualiz at ion product s 4 .5.1. St orage pools A storage pool is a file, directory, or storage device managed by lib virt for the purpose of providing storage to virtual machines. Storage pools are divided into storage volumes that store virtual machine images or are attached to virtual machines as additional storage. Multiple guests can share the same storage pool, allowing for better allocation of storage resources. Refer to the Red Hat Enterprise Linux 6 Virtualization Administration Guide for more information. Lo cal st o rag e p o o ls Local storage pools are directly attached to the host server. They include local directories, directly attached disks, physical partitions, and LVM volume groups on local devices. Local storage pools are useful for development, testing and small deployments that do not require migration or large numbers of virtual machines. Local storage pools may not be suitable for many production environments as they do not support live migration. N et wo rked ( sh ared ) st o rag e p o o ls Networked storage pools include storage devices shared over a network using standard protocols. Networked storage is required when migrating virtual machines between hosts with virt - man ag er, but is optional when migrating with vi rsh. Networked storage pools are managed by lib virt . 4 .5.2. St orage volumes Storage pools are further divided into storage volumes. Storage volumes are an abstraction of physical partitions, LVM logical volumes, file-based disk images and other storage types handled by lib virt . Storage volumes are presented to virtual machines as local storage devices regardless of the underlying hardware. 4 .5.3. Emulat ed st orage devices The host emulates a range of storage devices that can be presented to virtual machines. Each type of storage device is appropriate for specific use cases. Choice between different types of storage devices allows for maximum flexibility and compatibility with guest operating systems. virt io - scsi virtio-scsi is the recommended para-virtualized storage device for guests using large numbers of disks, or advanced storage features such as TRIM. virt io - b lk virtio-blk is a para-virtualized storage device suitable for exposing image files to guests. virtio-blk can provide the best disk I/O performance for virtual machines, but has fewer features than virtio-scsi. ID E ID E is recommended for legacy guests that do not support virtio drivers. ID E performance is lower than virtio-scsi or virtio-blk, but it is widely compatible with different systems. CD-RO M ATAPI CD -ROMs and virtio-scsi CD -ROMs are available for presenting ISO files or the host CD -ROM drive to guests. virtio-scsi CD -ROMs can be used with guests that have the virtioscsi driver installed. ATAPI CD -ROMs offer wider compatibility but lower performance. 21 Virt ualiz at ion G et t ing St art ed G uide U SB mass st o rag e d evices an d f lo p p y d isks USB mass storage devices and floppy disks are available when removable media is required. USB mass storage devices are preferable to floppy disks due to their larger capacity. 4 .5.4 . Host st orage D isk images can be stored on a range of local and remote storage technologies connected to the host. Imag e f iles Image files are stored on a host file system. The image files can be stored on a local file system, such as ext4 or xfs, or a network file system, such as NFS. Tools such as lib g u est f s can manage, back up, and monitor files. D isk image formats on KVM include: raw Raw image files contain the contents of the disk with no additional metadata. Raw files can either be pre-allocated or sparse, if the host file system allows it. Sparse files allocate host disk space on demand, and are therefore a form of thin provisioning. Pre-allocated files are fully provisioned but have higher performance than sparse files. Raw files are desirable when disk I/O performance is critical and transferring the image file over a network is rarely necessary. q co w2 qcow2 image files offer a number of advanced disk image features including backing files, snapshots, compression, and encryption. They can be used to instantiate virtual machines from template images. qcow2 files are typically more efficient to transfer over a network, because only sectors written by the virtual machine are allocated in the image. LVM vo lu mes Logical volumes can be used for disk images and managed using the system's LVM tools. LVM offers higher performance than file systems because of its simpler block storage model. LVM thin provisioning offers snapshots and efficient space usage for LVM volumes, and can be used as an alternative to migrating to qcow2. H o st d evices Host devices such as physical CD -ROMs and raw disks or logical unit numbers (LUNs) can be presented to the guest. This allows a guest to use storage area network (SAN) or iSCSI LUNs, as well as local CD -ROM media, with good performance. Host devices can be used when storage management is done on a SAN instead of on hosts. D ist rib u t ed st o rag e syst ems Gluster volumes can be used as disk images. This allows high-performance clustered storage over the network. 22 Chapt er 4 . Int roduct ion t o Red Hat virt ualiz at ion product s Red Hat Enterprise Linux 6.5 and above includes native support for creating virtual machines with GlusterFS. This enables a KVM host to boot virtual machine images from GlusterFS volumes, and to use images from a GlusterFS volume as data disks for virtual machines. When compared to GlusterFS FUSE, the native support in KVM delivers higher performance. Note For more information on storage and virtualization, refer to the Red Hat Enterprise Linux 6 Virtualization Administration Guide. 23 Virt ualiz at ion G et t ing St art ed G uide Chapter 5. Virtualization Tools This chapter provides an introduction to the many tools available to assist with virtualization. 5.1. vi rsh virsh is a command line interface (CLI) tool for managing the hypervisor and guest virtual machines. The vi rsh command line tool is built on the lib virt management API and operates as an alternative to the q emu-kvm command and the graphical virt - man ag er application. The vi rsh command can be used in read-only mode by unprivileged users or, with root access, full administrative functionality. The vi rsh command is ideal for scripting virtualization administration. In addition the vi rsh tool is a main management interface for vi rsh guest domains and can be used to create, pause, and shut down domains, as well as list current domains. This tool is installed as part of the libvirt-client package. Note Refer to the Red Hat Enterprise Linux 6 Virtualization Administration Guide for more information about managing virtual machines with vi rsh. 5.2. vi rt-manag er virt-manager is a lightweight graphical tool for managing virtual machines. It provides the ability to control the life cycle of existing machines, provision new machines, manage virtual networks, access the graphical console of virtual machines, and view performance statistics. This tool ships in its own package called virt-manager. Note Refer to the Red Hat Enterprise Linux 6 Virtualization Administration Guide for more information about managing virtual machines with vi rt-manag er. 5.3. vi rt-i nstal l virt-install is a command line tool to provision new virtual machines. It supports both text-based and graphical installations, using serial console, SD L, SPICE, or VNC client/server pair graphics. Installation media can be local, or exist remotely on an NFS, HTTP, or FTP server. The tool can also be configured to run unattended and kickstart the guest when installation is complete, allowing for easy automation of installation. This tool is installed as part of the python-virtinst package. Note Refer to the Red Hat Enterprise Linux 6 Virtualization Host Configuration and Guest Installation Guide for more information about vi rt-i nstal l . 24 Chapt er 5. Virt ualiz at ion T ools 5.4 . g uestfi sh guestfish is a shell and command line tool for examining and modifying virtual machine disk images. This tool uses libguestfs and exposes all functionality provided by the g uestfs API. Warning Using g uestfi sh on running virtual machines can cause disk-image corruption. Use the g uestfi sh command with the --ro (read-only) option if the disk image is being used by a running virtual machine. Note Refer to the Red Hat Enterprise Linux 6 Virtualization Administration Guide for more information about g uestfi sh. 5.5. Ot her useful t ools The following tools are used to access a guest virtual machine's disk via the host. The guest's disk is usually accessed directly via the d i sk-i mag e file located on the host. However it is sometimes possible to gain access via the lib virt domain. The commands that follow are part of the lib virt domain and are used to gain access to the guest's disk image. g uestmo unt A command line tool used to mount virtual machine file systems and disk images on the host machine. Warning Using g uestmo unt in --r/w (read/write) mode to access a disk that is currently being used by a guest can cause the disk to become corrupted. D o not use g uestmo unt in --r/w (read/write) mode on live virtual machines. Use the g uestmo unt command with the --ro (read-only) option if the disk image is being used. vi rt-cat A command line tool that can be used to quickly view the contents of one or more files in a specified virtual machine's disk or disk image. This tool is installed as part of the libguestfstools package. vi rt-d f A command line tool used to show the actual physical disk usage of virtual machines, similar to the command line tool d f. Note that this tool does not work across remote connections. It is installed as part of the libguestfs-tools package. 25 Virt ualiz at ion G et t ing St art ed G uide vi rt-ed i t A command line tool used to edit files that exist on a specified virtual machine. This tool is installed as part of the libguestfs-tools package. Warning Using vi rt-ed i t on live virtual machines can cause disk corruption in the virtual machine. Although the vi rt-ed i t command will try to prevent users from editing files on live virtual machines, it is not guaranteed to catch all instances. D o not use vi rt-ed i t on a live virtual machine. vi rt-fi l esystems A command line tool used to discover file systems, partitions, logical volumes and their sizes in a disk image or virtual machine. One common use is in shell scripts, to iterate over all file systems in a disk image. This tool is installed as part of the libguestfs-tools package. This tool replaces vi rt-l i st-fi l esystems and vi rt-l i st-parti ti o ns. vi rt-i nspecto r A command line tool that can examine a virtual machine or disk image to determine the version of its operating system and other information. It can also produce XML output, which can be piped into other programs. Note that vi rt-i nspecto r can only inspect one domain at a time. This tool is installed as part of the libguestfs-tools package. vi rt-i nspecto r2 An alternative tool to vi rt-i nspecto r, written in C. This tool is installed as part of the libguestfs-tools package. vi rt-l s A command line tool that lists files and directories inside a virtual machine. This tool is installed as part of the libguestfs-tools package. vi rt-make-fs A command line tool for creating a file system based on a tar archive or files in a directory. It is similar to tools like mki so fs and mksq uashfs, but it can create common file system types such as ext2, ext3 and NTFS, and the size of the file system created can be equal to or greater than the size of the files it is based on. This tool is provided as part of the libguestfs-tools package. vi rt-p2v A graphical tool to convert physical machines into virtual machines. This tool is installed as part of the virt-v2v package in Red Hat Enterprise Linux 6.2 and later. vi rt-rescue A command line tool that provides a rescue shell and some simple recovery tools for unbootable virtual machines and disk images. It can be run on any virtual machine known to lib virt , or directly on disk images. This tool is installed as part of the libguestfs-tools package. 26 Chapt er 5. Virt ualiz at ion T ools Warning Using vi rt-rescue on running virtual machines can cause disk corruption in the virtual machine. vi rt-rescue attempts to prevent its own use on running virtual machines, but cannot catch all cases. Using the command with the --ro (read-only) option will not cause disk corruption, but may give strange or inconsistent results. Avoid using vi rt-rescue on a running virtual machine. vi rt-resi ze A command line tool to resize virtual machine disks, and resize or delete any partitions on a virtual machine disk. It works by copying the guest image and leaving the original disk image untouched. This tool is installed as part of the libguestfs-tools package. Important Using vi rt-resi ze on running virtual machines can give inconsistent results. It is best to shut down virtual machines before attempting to resize them. vi rt-sysprep A command line tool to reset, customize, or unconfigure virtual machines to prepare a template for creating clones. This tool is installed as part of the libguestfs-tools package. Important Virtual machines must be shut down before running vi rt-sysprep. To preserve a virtual machine's existing contents, snapshot, copy or clone the disk before running vi rt-sysprep. vi rt-tar A command line archive tool for downloading and uploading parts of a virtual machine's file system. This tool is commonly used for making backups, uploading data, reviewing guest activity, and fixing or customizing guests. This tool is installed as part of the libguestfs-tools package. Warning Using vi rt-tar with the -u (upload) option on running virtual machines can cause disk corruption in the virtual machine. vi rt-tar attempts to prevent its own use on running virtual machines, but cannot catch all cases. Using vi rt-tar with the -x (extract) option on running virtual machines will not cause disk corruption, but may give strange or inconsistent results. It is best to shut down virtual machines before attempting to extract files from them. 27 Virt ualiz at ion G et t ing St art ed G uide vi rt-to p A command line utility similar to to p, which shows statistics related to virtualized domains. This tool ships in its own package: virt-top. vi rt-v2v A graphical tool to convert virtual machines from Xen and VMware hypervisors to run on KVM. This tool ships in its own package: virt-v2v. vi rt-vi ewer A minimal tool for displaying the graphical console of a virtual machine via the VNC and SPICE protocols. This tool ships in its own package: virt-viewer. vi rt-what A shell script that detects whether a program is running in a virtual machine. This tool ships in its own package: virt-what. vi rt-who The virt-who package is a Red Hat Enterprise Linux host agent that queries lib virt for guest UUID s. It then passes that data to the local entitlement server for the purposes of issuing certificates. This tool ships in its own package: virt-who. vi rt-wi n-reg A command line tool to export and merge Windows Registry entries from a Windows virtual machine, and perform simple Registry operations. This tool is installed as part of the libguestfs-tools package. Warning Using vi rt-wi n-reg on running virtual machines will cause irreversible disk corruption in the virtual machine. vi rt-wi n-reg attempts to prevent its own use on running virtual machines, but cannot catch all cases. Warning Modifying the Windows Registry is an inherently risky operation, as the format is deliberately obscure and undocumented. Changes to the registry can leave the system unbootable, so ensure you have a reliable backup before you use the -merg e option. vi rt-xml -val i d ate A command line tool to validate lib virt XML files for compliance with the published schema. This tool is installed as part of the libvirt-client package. 28 Appendix A. Revision Hist ory Appendix A. Revision History R evisio n 1.1- 5 Version for 6.7 GA release Mo n Ju l 14 2015 R evisio n 1.1- 03 T h u rs Ap r 16 2015 Preparing document for 6.7 Beta publication. Jiri H errman n D ayle Parker R evisio n 1.1- 02 Wed Mar 18 2015 Sco t t R ad van Add list of commands affected by lack of remote libguestfs support in 6.x. BZ #1070166. R evisio n 1.0- 16 Edited typo in libvirt section. T h u rs Mar 5 2015 D ayle Parker R evisio n 1.0- 15 Version for 6.6 GA release. Fri O ct 10 2014 D ayle Parker R evisio n 1.0- 12 T u e O ct 07 2014 Sco t t R ad van Apply SME feedback on guestfish manipulation of images from BZ #1043235. R evisio n 1.0- 11 T h u rs Au g 28 2014 Made minor clarity and accuracy fixes forBZ #1043235. Jo d i B id d le R evisio n 1.0- 10 Fri Au g 8 2014 D ayle Parker Build for beta release. Added reference to the Virtualization Tuning and Optimization Guide to performance section. R evisio n 1.0- 04 Mo n Ju ly 28 2014 D ayle Parker Revised documentation suite list, updated links for BZ #1043235. Added sections describing emulated storage devices and host storage for BZ #971226. R evisio n 1.0- 03 Wed Ju ly 16 2014 Added QXL driver description for BZ #1097974. D ayle Parker R evisio n 1.0- 02 Fri Ju n e 6 2014 D ayle Parker Edited performance section for BZ #1097973. Updated support limit URLs under " KVM guest virtual machine compatibility" for BZ #1097627. R evisio n 1.0- 01 Fri May 30 2014 Updated guest CPU models section for BZ #1097621. D ayle Parker R evisio n 0.3- 4 3 Version for 6.5 GA release. D ayle Parker Fri N o v 15 2013 R evisio n 0.3- 4 2 Fri O ct 18 2013 D ayle Parker Removed Windows 2003 from virtio-scsi support list in Para-virtualized devices section. R evisio n 0.3- 4 1 Wed O ct 2 2013 Removed edition number from front page. D ayle Parker R evisio n 0.3- 4 0 D ayle Parker Wed Sep t 25 2013 29 Virt ualiz at ion G et t ing St art ed G uide Minor edits for beta release. R evisio n 0.3- 39 Mo n Sep t 16 2013 D ayle Parker Minor wording edit to disk I/O throttling description for BZ #991252. Included Red Hat Enterprise Linux 6.4 benchmark details for BZ #919330. R evisio n 0.3- 36 T h u rs Sep t 12 2013 D ayle Parker Added disk I/O throttling description for BZ #991252. Revised GlusterFS description based on SME feedback for BZ #979271. R evisio n 0.3- 33 Mo n Sep t 9 2013 D ayle Parker Added GlusterFS description for BZ #979271. Removed Hypervisor D eployment Guide from documentation list. R evisio n 0.3- 32 Mo n Sep t 2 2013 D ayle Parker Corrected terminology in Para-virtualized devices section for BZ #983371. Edited Hyper-V Enlightenment description for BZ #923342. R evisio n 0.3- 31 Fri Au g u st 30 2013 Included Hyper-V Enlightenment description for BZ #923342. D ayle Parker R evisio n 0.3- 30 T u e Au g u st 20 2013 D ayle Parker Corrected terminology in Para-virtualized devices section for BZ #983371. R evisio n 0.3- 29 T h u rs Au g u st 15 2013 D ayle Parker Added list of virtual disk image formats supported for conversion by vi rt-v2v to section 2.3, including VHD X, VMD K and OVF - BZ #982846. Added description of virt-sysprep to section 5.5 for BZ #988156. R evisio n 0.3- 28 Mo n Au g u st 12 2013 Added Hyper-V to section 2.3 for BZ #990333. D ayle Parker R evisio n 0.3- 25 Fri Ap r 26 2013 Added documentation suite list to Chapter 1. D ayle Parker R evisio n 0.3- 24 Version for 6.4 GA release. Mo n Feb 18 2013 D ayle Parker R evisio n 0.3- 20 Updated 4.4.1 Storage pools. T h u rs Jan 31 2013 D ayle Parker R evisio n 0.3- 18 T u e Jan 29 2013 D ayle Parker Updated virtio-scsi support details in 4.3.2. Para-virtualized devices for BZ #903891. R evisio n 0.3- 16 Wed Jan 16 2013 Minor grammatical edits in virtualization products chapter. D ayle Parker R evisio n 0.3- 15 T u es N o v 27 2012 Minor grammatical edits throughout book. D ayle Parker R evisio n 0.3- 13 D ayle Parker 30 T h u O ct 18 2012 Appendix A. Revision Hist ory Applied SME feedback to RHEV introduction for BZ #798104. Revised virtualization guide descriptions in introduction. R evisio n 0.3- 11 Wed O ct 17 2012 D ayle Parker Made corrections, revised RHEV section in 1.3, added virtualization benchmarks in 3.3 for BZ #798104. Added virtualization deployment scenarios for BZ #847924. R evisio n 0.3- 10 Mo n O ct 8 2012 Revised 1.3 RHEV description in introduction for BZ #798104. D ayle Parker R evisio n 0.3- 8 T h u rs O ct 4 2012 D ayle Parker Added tech preview note about virtio-scsi in Ch.4 from SME review. Added QEMU Guest Agent description. Moved configuration-specific part of 4.3.4. Guest CPU Models to Virtualization Host Configuration and Guest Installation Guide for BZ #842970. R evisio n 0.3- 7 Wed O ct 3 2012 D ayle Parker Applied peer feedback to Virtualization in Red Hat Enterprise Linux introduction. Added virtio-scsi description for BZ #847167. R evisio n 0.3- 6 T u e Sep 25 2012 Added Section 1.2: Virtualization in Red Hat Enterprise Linux 6. D ayle Parker R evisio n 0.3- 5 Mo n Sep 3 2012 Added reference to Virt Security Guide in Ch.3 - BZ #838009. D ayle Parker R evisio n 0.3- 2 Wed Au g 29 2012 D ayle Parker Corrected links from http://docs.redhat.com/ to new location: http://access.redhat.com/knowledge/docs/ Corrected migration details in sections: 2.2. Migration and 4.4.1. Storage pools for BZ #831901. R evisio n 0.3- 1 Mo n Au g 27 2012 D ayle Parker Placed references to other guides in admonitions; corrected terms for BZ #813620. R evisio n 0.2- 83 Version for 6.3 GA release. Mo n Ju n e 18 2012 D ayle Parker R evisio n 0.2- 82 Mo n Ju n e 18 2012 Corrected " 64 vCPUs" to " 160 vCPUs" for BZ #832415. D ayle Parker R evisio n 0.2- 80 T u es Ju n e 12 2012 Clarified emulated watchdog device section for BZ #827307. D ayle Parker R evisio n 0.2- 78 Fri Ju n e 8 2012 Corrected typos and markup for BZ #827305. General corrections made to Chapter 4 BZ #827307. D ayle Parker R evisio n 0.2- 73 Mo n Ap ril 23 2012 Corrections made to chapter 5 (BZ #798108). Lau ra N o vich 31 Virt ualiz at ion G et t ing St art ed G uide R evisio n 0.2- 72 Mo n Ap ril 23 2012 Corrections made to chapter 4 (BZ #798106). Lau ra N o vich R evisio n 0.2- 71 T h u r Ap ril 19 2012 Corrections made to chapter 5 (BZ #798108). Lau ra N o vich R evisio n 0.2- 6 9 Wed Ap ril 18 2012 Corrections made to chapter 4 (BZ #798106). Lau ra N o vich R evisio n 0.2- 6 8 T u e Ap ril 17 2012 D ayle Parker Corrected terminology to " virtual machine" where needed (BZ #798063). R evisio n 0.2- 6 4 Mo n Ap ril 2 2012 Corrections to Chapter 2 (BZ #800401). Lau ra N o vich R evisio n 0.2- 6 1 Fri March 30 2012 D ayle Parker Made corrections in Chapter 3: Advantages (BZ #800409). Adjusted terms to " virtual machine" and " virtualized guest" where appropriate; corrected outdated link in 4.1; corrected terms in Emulated network devices (from drivers) in (BZ #798063). R evisio n 0.2- 52 Wed Jan u ary 11 2012 BZ #772859 clarified acronym. Jacq u elyn n East R evisio n 0.2- 51 BZ #750969 minor typos. Jacq u elyn n East Fri N o vemb er 4 2011 R evisio n 0.2- 4 7 Fri O ct o b er 14 2011 BZ #744156 added paragraph about emulated watchdogs. Jacq u elyn n East R evisio n 0.2- 4 4 BZ #734614 Fri Sep t emb er 16 2011 Jacq u elyn n East R evisio n 0.2- 4 3 BZ #734618 minor edit. Fri Sep t emb er 16 2011 Jacq u elyn n East R evisio n 0.2- 37 BZ #734619, BZ #734614 Fri Sep t emb er 2 2011 Jacq u elyn n East R evisio n 0.2- 34 T h u Sep t emb er 1 2011 Jacq u elyn n East BZ #734619, BZ #734511, BZ #734618, BZ #734616, BZ #715476, BZ #734613 R evisio n 0.2- 33 Wed Au g u st 31 2011 BZ #734618, BZ #734613, BZ #734619 Jacq u elyn n East R evisio n 0.2- 22 Wed Ju ly 27 2011 Advantages chapter completed (BZ #715476). Jacq u elyn n East R evisio n 0.2- 17 Mo n Ju ly 25 2011 Minor edits for BZ #715473 and BZ #715474. Jacq u elyn n East R evisio n 0.2- 15 Jacq u elyn n East 32 Mo n Ju ly 25 2011 Appendix A. Revision Hist ory Chapter 4 draft BZ #715476. R evisio n 0.1- 1 Wed May 4 2011 Sco t t R ad van Arranged basic layout and book infrastructure. Imported introductory text. R evisio n 0.0- 1 Wed May 4 2011 Initial creation of book by Publican. Sco t t R ad van 33
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