#virsh edit [vdomname]

(abbr)
<os>
  <boot dev='cdrom'/>
  <bootmenu enable='yes'/>
</os>

(abbr)

<devices>

    (abbr)

    <disk type='file' device='cdrom'>
      <driver name='qemu'/>
      <source file='/var/lib/libvirt/images/CentOS-5.5-x86_64-LiveCD.iso'/>
      <target dev='hdc' bus='ide'/>
      <readonly/>
    </disk>

    (abbr)

  </devices>

# virsh define /etc/libvirt/qemu/test1.xml

# virsh start test1; virsh console test1