Magic SysRQ key

Hi Folks, it's the first time that I see this kind of stuff : magic SysRQ Key .
It provides a way to send commands directly to the kernel through the /proc filesystem.

Quoted:
It is a 'magical' key combo you can hit which the kernel will respond to
regardless of whatever else it is doing, unless it is completely locked up.

It is enabled via a kernel compile time option, CONFIG_MAGIC_SYSRQ, which seems to be standard on most distributions.
So if you're administrating a remote server and suddenly it doesn't respond to commands, like for example :

you need a "magic command".
So, first you must activate the magic SysRq option:

And then you may reboot your system in such way:

Isn't it really cool ?
If you wanna learn more about magic SysRq you can read the sysrq.txt file in the kernel documentation.

UPGRADE:
of course if you wanna start it during the boot using sysctl you can by typing: