You can start or stop running domains at any time. Domain0 waits for all running domains to shutdown before restarting. You must place the configuration files of the domains you wish to shut down in the /etc/xen/ directory. All the domains that you want to start at boot time must be symbolically linked to /etc/xen/auto.

chkconfig xendomains on

The chkconfig xendomains on command does not automatically start domains; instead it will start the domains on the next boot.

chkconfig xendomains off

The chkconfig xendomains off terminates all running domains and does not start them again during the next boot.