10.7.3.1. ...starting Xen guest domains automatically at boot time?
Xen configuration files created with xenguest-install are installed in /etc/xen , and the filenames match the guest domain names. If these files are symlinked to the /etc/xen/auto directory, they will be started automatically at boot time by the xendomains service.
For example, to start the fedora guest domain automatically at each boot, link its configuration file using ln -s :
# ln -s /etc/xen/ fedora /etc/xen/auto