Linux Tipps und Tricks
From Lolly's Wiki
Hard reboot
This is the hard way to kick your kernel into void. No filesystem sync is done, just an ugly fast direkt reboot!
# echo 1 > /proc/sys/kernel/sysrq
# echo b > /proc/sysrq-trigger
First line enables sysrq, second line sends the reboot request.
For more look at kernel.org!