Setup KVM in Ubuntu

Also refer to Ubuntu help

Pre-installation checklist

Check that your CPU supports hardware virtualization

To run KVM, you need a processor that supports hardware virtualization. Intel and AMD both have developed extensions for their processors, deemed respectively Intel VT-x (code name Vanderpool) and AMD-V (code name Pacifica). To see if your processor supports one of these, you can review the output from this command:

egrep -c '(vmx|svm)' /proc/cpuinfo

If 0 it means that your CPU doesn't support hardware virtualization.

If 1 or more it does - but you still need to make sure that virtualization is enabled in the BIOS.

On my server :

$ egrep -c '(vmx|svm)' /proc/cpuinfo

4

$ sudo apt-get install cpu-checker

$ sudo /usr/sbin/kvm-ok

INFO: /dev/kvm does not exist
HINT:   sudo modprobe kvm_intel
INFO: Your CPU supports KVM extensions
INFO: KVM (vmx) is disabled by your BIOS
HINT: Enter your BIOS setup and enable Virtualization Technology (VT),
      and then hard poweroff/poweron your system
KVM acceleration can NOT be used

Very important :

In BIOS, you should find your Virtualization setting on the last option in the Advanced Tab, Under CPU Configuration -> "Intel Virtualization Technology". The option is disabled by default and needs to be enabled.

After enabled Virtualization Technology in BIOS setup

$ sudo /usr/sbin/kvm-ok
[sudo] password for lo:
INFO: /dev/kvm exists
KVM acceleration can be used

You can still run virtual machines, but it'll be much slower without the KVM extensions.

NOTE: You may see a message like "KVM acceleration can/can NOT be used". This is misleading and only means if KVM is *currently* available (i.e. "turned on"), *not* if it is supported.

Use a 64 bit kernel (if possible)

Running a 64 bit kernel on the host operating system is recommended but not required.

1. To serve more than 2GB of RAM for your VMs, you must use a 64-bit kernel (see 32bit_and_64bit). On a 32-bit kernel install, you'll be limited to 2GB RAM at maximum for a given VM.
2. Also, a 64-bit system can host both 32-bit and 64-bit guests. A 32-bit system can only host 32-bit guests.

To see if your processor is 64-bit, you can run this command:

egrep -c ' lm ' /proc/cpuinfo

If 0 is printed, it means that your CPU is not 64-bit.

If 1 or higher, it is. Note: lm stands for Long Mode which equates to a 64-bit CPU.

Now see if your running kernel is 64-bit, just issue the following command:

uname -m

x86_64 indicates a running 64-bit kernel. If you use see i386, i486, i586 or i686, you're running a 32-bit kernel.

Note: x86_64 is synonymous with amd64.

On my server :

$ egrep -c ' lm ' /proc/cpuinfo

4

$ uname -m

x86_64

Installation of KVM

Install Necessary Packages

For the following setup, we will assume that you are deploying KVM on a server, and therefore do not have any X server on the machine.

You need to install a few packages first:

Lucid (10.04) or later

$ sudo apt-get install qemu-kvm libvirt-bin ubuntu-vm-builder bridge-utils

Karmic (9.10) or earlier

$ sudo aptitude install kvm libvirt-bin ubuntu-vm-builder bridge-utils

• libvirt-bin provides libvirtd which you need to administer qemu and kvm instances using libvirt
• qemu-kvm (kvm in Karmic and earlier) is the backend
• ubuntu-vm-builder powerful command line tool for building virtual machines
• bridge-utils provides a bridge from your network to the virtual machines

You might also want to install virt-viewer, for viewing instances.

Add Users to Groups

Karmic (9.10) and later

You need to ensure that your username is added to the group libvirtd:

$ sudo adduser `id -un` libvirtd
Adding user '<username>' to group 'libvirtd' ...

After this, you need to relogin so that your user becomes an effective member of the libvirtd group. The members of this group can run virtual machines. (You can also 'newgrp kvm' in a terminal, but this will affect only that terminal.)

On my server :

$ sudo adduser `id -un` libvirtd

The user <username> is already a member of `libvirtd'.

Verify Installation

You can test if your install has been successful with the following command:

$ virsh -c qemu:///system list
 Id Name                 State
----------------------------------

$

If on the other hand you get something like this:

$ virsh -c qemu:///system list
libvir: Remote error : Permission denied
error: failed to connect to the hypervisor
$

Something is wrong (e.g. you did not relogin) and you probably want to fix this before you move on. The critical point here is whether or not you have write access to /var/run/libvirt/libvirt-sock.

The sock file should have permissions similar to:

$ sudo ls -la /var/run/libvirt/libvirt-sock
srwxrwx--- 1 root libvirtd 0 2010-08-24 14:54 /var/run/libvirt/libvirt-sock

Also, /dev/kvm needs to be in the right group. If you see:

 $ ls -l /dev/kvm
crw-rw----+ 1 root root 10, 232 Jul  8 22:04 /dev/kvm

You might experience problems when creating a virtual machine. Change the device's group to kvm/libvirtd instead:

sudo chown root:libvirtd /dev/kvm

Please note that /dev/kvm will not exist, if Virtualization Technology (VT) is disabled in BIOS setup

On my server 

ls -ld /dev/kvm

crw-rw----+ 1 root kvm 10, 232 Apr  1 01:00 /dev/kvm

If needed, you can try create this file by running :

sudo mknod /dev/kvm c 10 232

sudo chown root:libvirtd /dev/kvm

Now you need to either relogin or restart the kernel modules:

rmmod kvm
modprobe -a kvm

Optional: Install virt-manager (graphical user interface)

If you are working on a desktop computer you might want to install a GUI tool to manage virtual machines.

$ sudo apt-get install virt-manager

Virtual Machine Manager will appear in Applications -> System Tools menu. First create a new connection to local QEMU instance from File -> Add Connection menu. Localhost (QEMU) should appear in the virtual machine list. Note: there already exist Localhost (QEMU Usermode) connection but this does not work at least on Ubuntu 10.04.

Create a new virtual machine by pressing the top left Create a new virtual machine toolbar button.