You can find first hints for a backup of UCS in Univention’s wiki or support db.
Complete rebuild of a UCS system on new hardware
http://sdb.univention.de/content/10/20/en/complete-rebuild-of-a-ucs-system-on-new-hardware.html
Cool Solution - Single Server Backup and Restore
http://wiki.univention.de/index.php?title=Cool_Solution_-_Single_Server_Backup_and_Restore
And if you want to restore the system, you might need to use chroot:
http://wiki.univention.de/index.php?title=Cool_Solution_-_Migrating_a_native_UCS_installation_to_UVMM#Chroot_into_the_system