Clonagem de VMs

Instalar

apt-get install python-virtinst virt-clone

virt-clone --connect qemu://system -o dnocs11 -n dnocs11 -f /var/lib/libvirt/images/dnocs12.img

Iniciar com:

virsh --connect qemu:///system
start dnocs12
quit

E conectar ao virt-manager no desktop para gerenciar ou via SSH.

virt-clone -o lenny -n 'Nome Nova VM' -f 'arquivo da nova vm.img'

Referência: 
Installing KVM Guests With virt-instaOn Ubuntu 11.04 Server do Falko Timme
http://www.howtoforge.com/installing-kvm-guests-with-virt-install-on-ubuntu-11.04-server