CentOS / Redhat: Install KVM Virtualization Software

KVM (Kernel-based Virtual Machine) is a full virtualization solution for Linux on x86 hardware containing virtualization extensions Intel VT or AMD-V. How do I install KVM under CentOS or Red Hat Enterprise Linux version 5.5?

The Linux kernel 2.6.20 and above included KVM. RHEL 5.5 (and upcoming RHEL 6) supports KVM out of box and it has also been ported to FreeBSD as a loadable kernel module. However, this tutorial is tested on both CentOS and RHEL 5.5 only running 64 bit Intel Xeon CPU (with Intel VT) and 64 bit kernels with SELinux running in enforcing mode.

Why KVM?

XEN allows several guest operating systems to execute on the same computer hardware and it is also included with RHEL 5.5. But, why use KVM over XEN? KVM is part of the official Linux kernel and fully supported by both Novell and Redhat. Xen boots from GRUB and loads a modified host operating system such as RHEL into the dom0 (host domain). KVM do not have concept of dom0 and domU. It uses /dev/kvm interface to setup the guest operating systems and provides required drivers. See the official wiki for more information.

Required Packages

You must install the following packages:

  1. kmod-kvm : kvm kernel module(s)
  2. kvm : Kernel-based Virtual Machine
  3. kvm-qemu-img : Qemu disk image utility
  4. kvm-tools : KVM debugging and diagnostics tools
  5. python-virtinst : Python modules and utilities for installing virtual machines
  6. virt-manager : Virtual Machine Manager (GUI app, to install and configure VMs)
  7. virt-viewer: Virtual Machine Viewer (another lightweight app to view VM console and/or install VMs)
  8. bridge-utils : Utilities for configuring the Linux Ethernet bridge (this is recommended for KVM networking)

KVM Package Group

RHEL comes with KVM software group which includes full virtualization support with KVM. You can list all packages in the group as follows:
# yum groupinfo KVM
Sample outputs:

Loaded plugins: rhnplugin, security
Setting up Group Process

Group: KVM
 Description: Virtualization Support with KVM
 Mandatory Packages:
 Default Packages:
 Optional Packages:

A Note About libvirt

libvirt is an open source API and management tool for managing platform virtualization. It is used to manage Linux KVM and Xen virtual machines through graphical interfaces such as Virtual Machine Manager and higher level tools such as oVirt. See the official website for more information.

A Note About QEMU

QEMU is a processor emulator that relies on dynamic binary translation to achieve a reasonable speed while being easy to port on new host CPU architectures. When used as a virtualizer, QEMU achieves near native performances by executing the guest code directly on the host CPU. QEMU supports virtualization when executing under the Xen hypervisor or using the KVM kernel module in Linux. When using KVM, QEMU can virtualize x86, server and embedded PowerPC, and S390 guests. See the official website for more information.

A Note About Virtio Drivers

Virtio is paravirtualized drivers for kvm/Linux. With this you can can run multiple virtual machines running unmodified Linux or Windows VMs. Each virtual machine has private virtualized hardware a network card, disk, graphics adapter, etc. According to Redhat:

Para-virtualized drivers enhance the performance of fully virtualized guests. With the para-virtualized drivers guest I/O latency decreases and throughput increases to near bare-metal levels. It is recommended to use the para-virtualized drivers for fully virtualized guests running I/O heavy tasks and applications.

Host Operating System

Your main operating system such as CentOS or RHEL is known as host operating system. KVM is a Linux kernel module that enables a modified QEMU program to use hardware virtualization. You only need to install KVM under host operating systems.

KVM Domains

It is nothing but a guest operating system running under host operating system. Each kvm domain must have a unique name and ID (assigned by system).

Guest Operating Systems

KVM supports various guest operating systems such as

  1. MS-Windows 2008 / 2000 / 2003 Server
  2. MS-Windows 7 / Vista / XP
  3. FreeBSD
  4. OpenBSD
  5. Sun Solaris
  6. Various Linux distributions.
  7. NetBSD
  8. MINIX
  9. QNX
  10. MS DOS
  11. FreeDOS
  12. Haiku
  13. Amiga Research OS

Install KVM

Type the following command to install KVM under RHEL or CentOS:
# yum install kvm virt-viewer virt-manager libvirt libvirt-python python-virtinst
# yum groupinstall KVM

Important Configuration And Log Files (Directories) Location

The following files are required to manage and debug KVM problems:

  1. /etc/libvirt/ – Main configuration directory.
  2. /etc/libvirt/qemu/ – Virtual machine configuration directory. All xml files regarding VMs are stored here. You can edit them manually or via virt-manager.
  3. /etc/libvirt/qemu/networks/ – Networking for your KVM including default NAT. NAT is only recommended for small setup or desktops. I strongly suggest you use bridged based networking for performance.
  4. /etc/libvirt/qemu/networks/default.xml – The default NAT configuration used by NAT device virbr0.
  5. /var/log/libvirt/ – The default log file directory. All VM specific logs files are stored here.
  6. /etc/libvirt/libvirtd.conf – Master libvirtd configuration file.
  7. /etc/libvirt/qemu.conf – Master configuration file for the QEMU driver.


By default libvirt does not opens any TCP or UDP ports. However, you can configure the same by editing the /etc/libvirt/libvirtd.conf file. Also, VNC is configured to listen on by default. To make it listen on all public interfaces, edit /etc/libvirt/qemu.conf file.

Our Sample Setup

                                                                             +-------------> vm#1 ( /, CentOS MySQL Server)
                                                                             +-------------> vm#2 ( /, FreeBSD 7 Web Server)
LAN --> Switch    -->  eth0 --> -+                             |
                                 | ---> br0 -+      +----------------+       +-------------> vm#3 ( /, OpenBSD 4.x Firewall )
                                 |           | ===> |   RHEL Server  |  -----+  
                                 |           |      |      KVM       |       +-------------> vm#4 ( /, Solaris 10 Testing Server )
                                 | ---> br1 -+      +----------------+       |     
Wan --> ISP Router --> eth1 --> -+                               +-------------> vm#5 ( /, Windows Server Testing Server )
                                                                             +-------------> vm#6 ( /, RHEL Mail Server )

(Fig.01: Our sample server setup – you need to scroll to see complete diagram)


Host Configuration

  • OS – RHEL / CentOS v5.5 is our host operating system.
  • Host has two interface eth0 and eth1
  • LAN – eth0 with private ip
  • Internet – eth1 with public IPv4/IPv6 address.
  • Disk – 73×4 – 15k SAS disk in RAID 10 hardware mode. All VMs are stored on same server (later I will cover SAN/NFS/NAS configuration with live migration).
  • RAM – 16GB ECC
  • CPU – Dual core dual Intel Xeon CPU L5320 @ 1.86GHz with VT enabled in BIOS.

Virtual Machine Configuration

  • Bridged mode networking (eth0 == br0 and eth1 == br1) with full access to both LAN and Internet.
  • Accelerator virtio drivers used for networking (model=virtio)
  • Accelerator virtio drivers for disk (if=virtio) and disk will show up as /dev/vd[a-z][1-9] in VM.
  • Various virtual machines running different guest operating systems as per requirements.

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🐧 35 comments so far... add one

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35 comments… add one
  • Zdenek Styblik Jun 13, 2010 @ 10:23

    The heading should read ‘virtualization’.
    Not bad summary though.

  • qt2r Jun 14, 2010 @ 11:43

    Excellent guide. thanks for sharing :)

  • cod3fr3ak Jun 14, 2010 @ 15:41

    Which gives better results with non-virtual aware operating system, xen or kvm. I can never remember. I am considering trying to run Windows 7 within a xen or kvm instance on Centos 5.5. Does anyone know if it supports Directx? A couple of the games I play use it for 3d and effects rendering.

    • fred Jan 19, 2013 @ 0:09

      hi cod3fr3ak,
      did you get any answers on your question about xen or kvm supporting directx?
      i’m having the same problem…
      thx in advance

  • Bhaskar Chowdhury Jun 16, 2010 @ 4:42

    Hey Vivek!
    This article is as good as others you have posted earlier.Keep up the good work man.Looking forward to the next installment of this article.

    Cheers mate!

  • Paul Jun 17, 2010 @ 7:48


    as far as I’m aware Novell does not yet support KVM, it is included in SLES11 sp1 as a “technology preview”, I think they call it, ie they include it for you to test but it is not supported, at least not officially.


    • Ian Jun 27, 2010 @ 10:49

      It was tech preview in sles11, fully supported in sles11sp1

  • mam Jun 22, 2010 @ 10:21

    I found error in one command yum groupinstall KMV, correct is yum groupinstall KVM

  • rwilla Aug 5, 2010 @ 6:49

    You can list all packages in the group as follows: #yum groupinfo Virtualization

  • Rocky Patel Oct 14, 2010 @ 16:45


    I m getting this error while installing yum groupinstall KVM..

    yum groupinstall KVM
    Loaded plugins: fastestmirror
    Loading mirror speeds from cached hostfile
    * addons: mirrors.hns.net.in
    * base: mirrors.hns.net.in
    * extras: mirrors.hns.net.in
    * updates: mirrors.hns.net.in
    Setting up Install Process
    Resolving Dependencies
    –> Running transaction check
    —> Package kvm.i386 0:36-1 set to be updated
    —> Package virt-manager.i386 0:0.6.1-12.el5 set to be updated
    –> Processing Dependency: python-virtinst >= 0.400.3 for package: virt-manager
    —> Package virt-viewer.i386 0:0.0.2-3.el5 set to be updated
    –> Running transaction check
    —> Package python-virtinst.noarch 0:0.400.3-9.el5_5.1 set to be updated
    –> Processing Conflict: libvirt conflicts kvm Finished Dependency Resolution
    libvirt-0.6.3-33.el5_5.3.i386 from installed has depsolving problems
    –> libvirt conflicts with kvm
    Error: libvirt conflicts with kvm
    You could try using –skip-broken to work around the problem
    You could try running: package-cleanup –problems
    package-cleanup –dupes
    rpm -Va –nofiles –nodigest
    The program package-cleanup is found in the yum-utils package.

  • Ice72 Dec 2, 2010 @ 8:58


    great summary. On fedora core 14 the “yum install ” command not install the qemu-kvm.x86_64 which is installed if I use the command “yum install virtualization”

  • Hanif Dec 30, 2010 @ 3:47

    How about if I want the vcpu more than 16 cores

  • alessandroo Jun 21, 2011 @ 8:48


    Is kvm available on RHEL 5.5 32 bits ?

    I have only a 32 bit processor…

    • 🐧 nixCraft Jun 21, 2011 @ 11:28

      Running a 64 bit kernel (RHEL 64 bit) on the host operating system is recommended but not required. You can use 32bit but limited to 2GB ram per VM. A 32 bit server can only host 32-bit guest operating system.

  • alessandroo Jun 21, 2011 @ 12:10

    ok thanks for this information, but its not really my request.
    I have a RHEL 5.5 32bits distribution (i have only a proc 32bits, i dont have the choice) in a plateform test and i need to install KVM.

    Is KVM compatible with a 32 bit distribution? Because i dont find the packet “kvm”, “libvirt”, “virt manager”

    • 🐧 nixCraft Jun 21, 2011 @ 12:20

      RHEL 5.5+ x86 removed 32bit kvm packages. Your options are as follows
      a) Go with 64bit (x64) RHEL system as Redhat not planned create 32bit KVM as most VM server runs on 64 bit platform.
      b) Go with 32 bit RHEL and compile new kernel with KVM
      c) Use Ubuntu or other 32 bit Linux distro that support 32bit KVM

  • abdullah kamal Aug 23, 2011 @ 16:06

    is it possible to create virtual data center in centos, currently this kind of technology is provided by the redhat.

  • Lio Sep 5, 2011 @ 18:00

    Hi all
    could anyone advise me to solve the problem
    the problem is as following:
    I’ve installed kvm with all its packages and when i want to install win 7 it will be stacked and does not go forward please help
    i’ll be appreciated

  • ahmad Sep 7, 2011 @ 9:09

    Please note that RedHat/CentOS was configured to run KVM only on 64-bit operating systems.

  • Ivan Sep 18, 2011 @ 14:50

    For the host Centos OS, what is the recommended installation configurations? (Server or Minimal)? I have chosen Minimal but couldn’t load any GUI for my centos…and is stuck at the step where it is suppose to load a GUI for virtual manager

  • Rashid Iqbal Oct 15, 2011 @ 19:28

    I want to change the default location of virtual harddisk to another LVM volume.

    How can I do this………?

  • luckysanj Nov 20, 2011 @ 9:18

    same thing from my side also….For the host Centos OS, what is the recommended installation configurations? (Server or Minimal)? I have chosen Minimal but couldn’t load any GUI for my centos…and is stuck at the step where it is suppose to load a GUI for virtual manager.

  • Sathish Jan 25, 2012 @ 18:13

    Thanks, its very helpful for me :)

  • kuljinder mathoun Feb 28, 2012 @ 18:42

    Do we have any equivalent application like VMware Virtual Center to manage KVM hosts?
    I heard about OVIRT but it has some limitation.


  • Rafi Mar 16, 2012 @ 2:10

    first thank you Vivek, for writing an article that brand new newbies could follow, nice organized. Further request to dumb it down by some server sizing how many CPUs, RAM etc especially for small cluster of 1-10 desktops (that is what we like to do)… also do you have articles on how to installed RHEL 64 on a brand new machine?

    Sorry folks, I have to start somewhere, I am staring at my RHEL 6.2 ISO images, new server no OS on it, 3.0 GHz CPU quad core and 16 GB RAM. Plugged in and I have no CLUE. I absolutely cannot stand the other techies speak nor understand it.

    Everything else I read, just went into total geekdom high brow type writeup/

    Vivek any dummy level article that goes step by step or any material I could read up on will be deeply appreciated!!!

  • Rafi Mar 16, 2012 @ 2:13

    Just saw your TOC some install stuff there, will try that… thanks!

  • aswin May 31, 2012 @ 10:17

    I have question, I already installed kvm at dell R720 12 Core with 64GB RAM and 4TB HDD SCSI with RAID5.
    Problem with windows guest OS when running with KVM, ethernet using virtio driver very slow performance, I copy from sharing folder 25Mb it took 60Minutes until finish.
    but running well wit Linux guest OS.

    info :
    Running in CentOS 6.2 x86_64 kernel 2.6.32-220.13.1.el6.x86_64
    lsmod :
    virtio_pci 6687 0
    virtio_net 15839 0
    virtio_ring 7729 2 virtio_pci,virtio_net
    virtio 4890 2 virtio_pci,virtio_net
    vhost_net 31384 2
    macvtap 9724 5 vhost_net
    macvlan 10180 1 macvtap
    tun 17051 5 vhost_net
    kvm_intel 50412 10
    kvm 305988 1 kvm_intel
    acpi_pad 87758 0

    Do you have any Idea, thank you..


  • Putchong Uthayopas Jun 3, 2012 @ 1:15

    Good start for KVM. Help me a lot. Thanks…

  • David Ramirez Nov 1, 2012 @ 15:59

    Thanks – a good lead-in into doing this for 1st time… even after coming from other commercial environments…

  • Lihar Shendi Wijaya Oct 29, 2013 @ 10:01

    I Very Like This Post :)

    i want ask question sir

    ifcfg-eth0 = ifcfg-br0
    ifcfg-eth1 = ifcfg-br1

    what is iptables nat use? interfaes iptables eth0 with eth1 or br0 with br1 ?

    thanks sir

  • sahil Jan 7, 2014 @ 11:37

    Hello Sir,

    Can we install KVM on Centos 32 bit base machine. ?
    I tried it on centos 6 32 bit using yum but Its says no package found for KVM.
    Please help

  • sudheer Jan 19, 2014 @ 11:14

    HI Guys,

    In my setup we need to configure both IPV4 and IPv6 on same KVM machine(Br0 for IPV4 and Br1 for IPV6 internal). Can some one who worked on this kind of setups please suggest me how to create bridges and guest network. I have configured as i IPV4 setup but very often the guests are not reachable from outside of the server.

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