Sometimes to reproduce a bug or verify a fix to libvirt, you want to
just be able to start a qemu VM under KVM, not really caring what it
does.  These instructions will get you there, assuming you are on a
standard Ubuntu ec2 image, as user ubuntu with libvirt and qemu
installed.

This will attach to a bridge called br0.  Change that name if you
need to.

 * wget http://people.canonical.com/~serge/cdboot.xml

 * Create the disk image:

{{{
qemu-img create cdboot.img 1G
}}}

 * Get a tiny bootable iso:

wget -O mini.iso http://archive.ubuntu.com/ubuntu/dists/precise/main/installer-amd64/current/images/netboot/mini.iso

 * Define the vm:

{{{
virsh define cdboot.xml
}}}

 * Now the vm should be able to start

{{{
virsh start cdboot
virsh list
  # this should show cdboot running.  you can connect probably as 'gvncviewer :0'
virsh destroy cdboot
}}}

 * To make this vm autostart,

{{{
virsh autostart cdboot
}}}