source : https://help.ubuntu.com/community/KVM/Installation
Installation
Pre-installation checklist
Check that your CPU supports hardware virtualizationTo 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/cpuinfoIf 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.By default, if you booted into XEN kernel it will not display svm or vmx flag using the grep command. To see if it is enabled or not from xen, enter:cat /sys/hypervisor/properties/capabilitiesYou must see hvm flags in the output.Alternatively, you may execute:kvm-ok which may provide an output like this:INFO: /dev/kvm exists KVM acceleration can be usedIf you see :INFO: Your CPU does not support KVM extensions KVM acceleration can NOT be usedYou 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.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.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/cpuinfoIf 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 -mx86_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.
Installation of KVM
Install Necessary PackagesFor 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:Cosmic (18.10) or later$ sudo apt-get install qemu-kvm libvirt-daemon-system libvirt-clients bridge-utilsLucid (10.04) or later$ sudo apt-get install qemu-kvm libvirt-bin ubuntu-vm-builder bridge-utilsKarmic (9.10) or earlier$ sudo aptitude install kvm libvirt-bin ubuntu-vm-builder bridge-utilslibvirt-bin provides libvirtd which you need to administer qemu and kvm instances using libvirtqemu-kvm (kvm in Karmic and earlier) is the backendubuntu-vm-builder powerful command line tool for building virtual machinesbridge-utils provides a bridge from your network to the virtual machinesYou might also want to install virt-viewer, for viewing instances.
Add Users to GroupsKarmic (9.10) and later (but not 14.04 LTS and 18.10)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.)Bionic (18.04 LTS) and higherThe group name is changed to libvirt, and you also need to be a member of ‘kvm’:$ sudo adduser `id -un` libvirt Adding user ‘<username>’ to group ‘libvirt’ … $ sudo adduser `id -un` kvm Adding user ‘<username>’ to group ‘kvm’ …Releases prior to Karmic (9.10)You need to ensure that your username is added to the groups: kvm and libvirtd.To check:$ groups adm dialout cdrom floppy audio dip video plugdev fuse lpadmin admin sambashare kvm libvirtdTo add your <username> to the groups:$ sudo adduser `id -un` kvm Adding user ‘<username>’ to group ‘kvm’ … $ sudo adduser `id -un` libvirtd Adding user ‘<username>’ to group ‘libvirtd’ …After the installation, you need to relogin so that your user becomes an effective member of kvm and libvirtd user groups. The members of this group can run virtual machines.
Verify InstallationYou can test if your install has been successful with the following command:$ virsh list –all Id Name State ———————————- $If on the other hand you get something like this:$ virsh list –all 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-sockAlso, /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/kvmYou might experience problems when creating a virtual machine. Change the device’s group to kvm/libvirtd instead:sudo chown root:libvirtd /dev/kvmNow 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-managerVirtual 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) or QEMU/KVM 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.
Version-specific Notes
8.10 (Intrepid) NotesTwo 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.
11.10 (Oneric) NotesSwitching to the server kernel might be helpful if there are start problems with virtual machines (i.e. Windows XP freezes approximately once every 5 starts )