You can reboot via telnet ('reboot'), via the WEB-IF or as a last resort, via the power switch at the back.
Reason I ask is because a number of 8k's have a hardware issue, causing trouble after a boot. A second boot (reboot) fixes it; there is even a plugin that does this job automated. See
Code:
http://forums.openpli.org/topic/36616-plugin-auto-reboot-et8000/#entry492822
but more have been reported (mine does the same).
Just give the plugin a try.