From Earlham Cluster Department
updateclient is the tool that is used on the client to trigger an imaging. It talks to the SystemImager server using rsync, and pulls down any changes to the filesystem. Optionally, it can then reinstall the bootloader and/or reboot the node.
The ACLs have a force-update.sh script in /root that is called every Sunday. It automates the process, as well as implements a delay based on the digits at the end of the short hostname (e.g. acl5 gets delayed 5*CONSTANT_FACTOR seconds).
Invoking updateclient naked goes something like this:
updateclient -server server.name.example.com -image image_name -override `hostname -s` -reboot
Rebooting is almost always required in our environment, because several services (such as ypbind) operate over a socket that rsync will delete.