Magic SysRq Key
(SysRq = Alt+PrtSc)

Key	Function
h	Print help.
0-9	Set log level.
l	Print backtrace.
t	Print tasks.
c	Crash(dump).
f	OOM killer.
r	Disable kbd raw mode.
e	SIGTERM all.
i	SIGKILL all.
s	Sync filesystems
u	Remount read-only.
b	Reboot.
o	Shut off.