Feature #370
Updated by Daniel Curtis about 10 years ago
KVM is a full virtualization solution for Linux on x86 (64-bit included) hardware containing virtualization extensions (Intel VT or AMD-V). It consists of a loadable kernel module, @kvm.ko@, that provides the core virtualization infrastructure and a processor specific module, @kvm-intel.ko@ or @kvm-amd.ko@. In Debian, Xen and VirtualBox are alternatives to KVM. h2. Installation Install the @qemu-kvm@ package with apt-get or aptitude, e.g. using this command: <pre> aptitude install qemu-kvm libvirt-bin </pre> The libvirt-bin daemon will start automatically at boot time and load the appropriate kvm modules, @kvm-amd@ or @kvm-intel@, which are shipped with the Linux kernel Debian package. If you intend create VMs from the command-line, install virtinst. In order to be able to manage virtual machines as regular user you should put this user into the libvirt group: <pre> adduser <youruser> libvirt </pre> h2. Setting up bridge networking It can be useful to set up a bridge for the KVM VMs as described here at QEMU page. h2. Managing VMs from the command-line You can then use the @virsh@(1) command to start and stop virtual machines. VMs can be generated using @virtinst@. For more details see the libvirt page. Virtual machines can also be controlled using the kvm command in a similar fashion to QEMU. h3. Example installation of a Guest CentOS instance <pre> virt-install \ -n myguest \ -r 2048 \ --vcpus=2 \ --os-variant=rhel6 \ -v \ --accelerate \ -c /var/lib/libvirt/images/CentOS-6.2-x86_64-minimal.iso \ -w bridge:br0 \ --vnc --vncport=7601 \ --disk path=/vm/guest.img,size=100 </pre> The above example uses the following parameters; 100 refers to 100GB for hard drive size, 2048 for MB of RAM, 2 vcpus, and a VNC server setup on port 7601. h3. Example installation of a Windows Server 2008 R2 <pre> # Place WinServ ISO into /storage/local/iso/ # Download VIRTIO driver iso image to use during install cd /storage/local/iso/ wget http://alt.fedoraproject.org/pub/alt/virtio-win/latest/images/bin/virtio-win-0.1-52.iso # Pre-create VM disk image qemu-img create -f qcow2 -o preallocation=metadata /storage/local/images/winserv1.qcow2 50G # Launch installation inside screen screen virt-install --connect qemu:///system --name WinServ1 --ram 2048 --vcpus 2 \ --disk path=/storage/local/images/winserv1.qcow2,format=qcow2,bus=virtio,cache=none \ --disk path=/storage/local/iso/virtio-win-0.1-52.iso,device=cdrom \ --cdrom /storage/local/iso/winserv.iso \ --network=bridge:vmbr0,model=e1000 \ --vnc --os-type=windows --os-variant=win2k8 \ --noautoconsole --accelerate --noapic --keymap=en-us # Detach screen CTRL+A+D # Run virt-manager for VNC display (make sure you have X forwarding enabled on your ssh session for remote display) virt-manager # OR virt-viewer -c qemu:///system WinServ1 </pre> h2. Managing VMs with a GUI On the other hand, if you want to use a graphical UI to manage the VMs, you can use the Virtual Machine Manager @virt-manager@. h2. Migrating guests to a Debian host h3. Migrating guests from RHEL/CentOS 5.x There are a few minor things in guest XML configuration files (/etc/libvirt/qemu/*.xml you need to modify: * Machine variable in <os> section should say pc, not rhel5.4.0 or similar * Emulator entry should point to /usr/bin/kvm, not /usr/libexec/qemu-kvm In other words, the relevant sections should look something like this: <pre> <os> <type arch='x86_64' machine='pc'>hvm</type> --- snip --- <devices> <emulator>/usr/bin/kvm</emulator> </pre> If you had configured a bridge network on the CentOS host, please refer to this wiki article on how to make it work on Debian. h2. Troubleshooting h3. No network bridge available @virt-manager@ uses a virtual network for its guests, by default this is routed to 192.168.122.0/24 and you should see this by typing ip route as root. If this route is not present in the kernel routing table then the guests will fail to connect and you will not be able to complete a guest creation. Fixing this is simple, open up @virt-manager@ and go to +Edit -> Host details -> Virtual networks+ tab. From there you may create a virtual network of your own or attempt to fix the default one. Usually the problem exists where the default network is not started. h3. cannot create bridge 'virbr0': File exists: To solve this probelm you may remove the virbr0 by running: <pre> brctl delbr virbr0 </pre> <pre> Open @virt-manager@ and go to +Edit Edit -> Host details -> Virtual networks+ networks start the default network. </pre> You can check the netstatus <pre> virsh net-list --all </pre> Optionally, you can use bridge network BridgeNetworkConnections h2. Resources * https://wiki.debian.org/KVM * http://www.linux-kvm.org/ * http://www.linux-kvm.org/page/HOWTO * http://opennodecloud.com/documentation/howtos/kvm-guests-virt-install-examples/