Posted on March 10th, 2012
If you got the system which cannot be rebooted traditional way for some reason (for example reboot command gives you “bus error”) you can use sysrq.
echo 1 > /proc/sys/kernel/sysrq echo s > /proc/sysrq-trigger echo u > /proc/sysrq-trigger echo b > /proc/sysrq-trigger
First command enables sysrq functionality, 2nd tries to sync filesystems, 3d to umounts them read-only (to avoid fsck during boot) and the last reboots the machine
Read Documentation/sysreq.txt in linux source directory for more options.