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:
