If you need to reboot a workstation, either because it has frozen or because it has been locked for more than 20 minutes, just follow the instructions below. Note that rebooting a workstation will cause any unsaved data to be permanently lost. If you encounter any trouble, please either contact a consultant, or report the problem to Athena Cluster Serivces (x3-1101 or firstname.lastname@example.org).
Press Ctrl-Alt-F1, which should cause the screen to switch to text mode (there may be some text displayed on the screen, or it may be blank). Then, press Ctrl-Alt-Delete. In a few seconds, the machine should begin rebooting.
If the previous method fails, you can try pressing the power button on the machine once. After a few seconds, the machine should begin shutting down, or it may bring up a dialog asking you what you want to do. Once it has powered itself off, you can turn it back on by pressing the power button again.
If all else fails, you can press and hold the power button on the machine for 5 seconds, which will immediately power it down. This will perform an unclean shutdown, and the machine will need to check its disk when it is powered back on, which will take longer than a normal start-up.