Magic SysRq

Magic SysRq (Magic System Request) is a kernel hack that enables the kernel to listen to specific key presses and respond by calling a specific kernel function. Magic SysRq is activated via input from the keyboard or a serial line.

Kernel
A basic Magic SysRq configuration:

Invocation
On and  systems the key combination of ++ will result in Magic SysRQ invocation. See the following table for some possible options:

More information can be found in the official Magic SysRQ Linux Kernel documentation.

External resources

 * http://www.linuxhowtos.org/Tips%20and%20Tricks/sysrq.htm
 * https://en.wikipedia.org/wiki/System_request - Some history on the system request key.