KVM guest management

Install packages

Debian or Ubuntu

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

Redhat or Fedora

• yum install kvm
• yum install virt-manager libvirt libvirt-python python-virtinst
• chkconfig libvirtd on
• service libvirtd start

KVM virsh cheat sheet!

This is a list of commands to use in the virsh cli.

To start the virsh cli run the following cmd:

$ virsh

or:

virsh --connect qemu:///system

KVM has its own commands, but we like to use virsh.

Here is a list comparing Xen and KVM (virsh) commands.

Virtual Serial Console configuration

From the KVM host run:

virsh edit <dom>

Then add the following inside the <device></device> directives:

<serial type="pty">
    <source path="/dev/pts/3" />
    <target port="1" />
</serial>

From the Guest run:

sudo cp -p /etc/init/tty06.conf /etc/init/ttyS0.conf
sudo vi /etc/init/ttyS0.conf
sudo diff /etc/init/tty06.conf /etc/init/ttyS0.conf

Vmbuilder Example

This example assumes ubuntu linux.

sudo apt-get install python-vm-builder

vmbuilder kvm ubuntu --help

VMNAME=mbison
mkdir /vms/$VMNAME

sudo vmbuilder kvm ubuntu --libvirt=qemu:///system --suite=lucid --flavour=virtual \
--hostname=$VMNAME --domain='foxhop.net' --rootsize='10240' --mem='1024' \
--ip=192.168.1.51 --gw=192.168.1.254 --dns=192.168.1.22 --bridge=br0 \
--addpkg=openssh-server --addpkg=acpid --timezone=EDT --verbose

VMNAME=cammy
mkdir /vms/$VMNAME

sudo vmbuilder kvm ubuntu       \
    --libvirt=qemu:///system    \
    --suite=lucid               \
    --arch=amd64 -o             \
    --flavour=virtual           \
    --hostname=$VMNAME          \
    --dest=/vms/$VMNAME         \
    --rootsize=20480            \
    --mem=1024                  \
    --bridge=br0                \
    --ip=192.168.1.52           \
    --gw=192.168.1.254          \
    --dns=192.168.1.22          \
    --user=john                 \
    --pass=doe                  \
    --addpkg=openssh-server     \
    --addpkg=acpid              \
    --timezone=EDT              \
    --verbose

Mounting a qcow2 image on the host

Sometimes it is helpful to be able to mount a drive image under the host system. For example, if the guest doesn't have network support, the only way to transfer files into and out of the guest will be by the storage devices it can address or to restore files from a backup image.

To mount qcow2 images there is (at least in F-11 qemu) very useful qemu-nbd util. It shares image through kernel network block device protocol and this allows to mount it:

sudo modprobe nbd max_part=63
sudo qemu-nbd -c /dev/nbd0 image.img
sudo mount /dev/nbd0p1 /mnt/image

Add another disk image to a guest

This is how you add an additional disk to a guest. In this example I will be adding a 20GB disk image to a guest dom named cammy.

fallocate -l 20g /vms/cammy/cammy-aux.img

or

qemu-img create -f qcow2 /vms/cammy/cammy-aux.img 20G

If you want to look that the image statistics try this command.

qemu-img info /vms/cammy/cammy-aux.img