Preflight check

How to check if your CPU supports hardware virtualisation

To run KVM, you need a processor that supports virtualisation; Intel and AMD both have developed extensions for their processors, respectively INTEL-VT and AMD-V. To see if your processor supports one of these, you can run the following command:

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

If nothing is printed, it means that your CPU doesn't support hardware virtualisation, in this case you can run qemu without KVM support. Otherwise, it does - but you still need to make sure that virtualisation is enabled in the BIOS.

Use a 64 bit kernel if you need more than 2GB RAM for your VMs

To serve more than 2047 MB 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.

To see if your processor is 64 bit, you can run the following command:

grep ' lm ' /proc/cpuinfo

If nothing is printed, it means that your CPU is not 64 bit. lm stands for Long Mode, so 64 bit CPU.

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

uname -m

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

Installation of KVM

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:

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

• libvirt-bin provides libvirtd which you need to administer qemu and kvm instances using libvirt
• kvm 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

8.10 (intrepid) Notes:

• Two meta packages have been added: ubuntu-virt-server and ubuntu-virt-mgmt. Ubuntu-virt-server installs the packages needed to setup a base virtulization host (kvm, libvirt-bin and openssh-server) and ubuntu-virt-mgmt installs what you need to administer it from a management station (virt-manager, python-vm-builder and virt-viewer).

• ubuntu-vm-builder has been replaced by python-vm-builder (tutorial).

Note: libdevmapper does not load its module when it is installed (bug 277648) , so you will either need to do a

•  $ sudo modprobe dm-loop 

or reboot your system before being able to use it.

Adding Users

Add yourself to the libvirtd group (note that there is no need to add yourself to the kvm group):

$ sudo adduser $USER libvirtd

This will give you access to the system-wide libvirtd instance. This is preferable for you because it gives you access to the advanced networking options rather than simply the "userspace networking" option as you may know it from QEmu.

Note: You need to log out and log back in for the new group membership to take effect.

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 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.

Note: You should also run the kvm command as root, which should give you the help message of kvm. If you get an error message complaining about the lack of Hardware Acceleration, it is probably disabled at the bios level. You should be able to confirm that by reading the last line of dmesg which should say kvm: disabled at bios level.

This is what it looks like when it works:

$ sudo kvm
QEMU PC emulator version 0.9.1 (kvm-62), Copyright (c) 2003-2008 Fabrice Bellard
usage: qemu [options] [disk_image]
...
$

You will get something like this when hardware acceleration is not supported by your CPU or disabled at bios level:

$ sudo kvm
Could not initialize KVM, will disable KVM support
Ubuntu does not support running KVM without hardware acceleration. Sorry.
$

Removing KVM

Removing kvm is pretty easy:

$ sudo apt-get purge kvm

This will unload the kvm modules, remove the kvm and purge its configuration (for example, files in /etc).

If kvm was already removed, the following will finally purge it:

$ sudo dpkg -P kvm