Suppose Linux "hung" on you in such a way that nothing works and not even the old trick of Ctrl + Alt + Del (to restart the system) or Ctrl + Alt + Backspace (to restart the graphics server) is to solve the problem. Of course, in that case, surely you are going to be tempted to press the shutdown or restart button, which would constitute a serious mistake, since this, while allowing you to get out of the way, turns off the system in a "messy" way.
A lesser known, but more elegant solution would be to press:
Right Alt + SysRq key and type the following:
REISUB
This will unmount your drives, terminate all processes, and reboot your computer peacefully.
To find out if this trick will work on your computer, I opened a terminal and typed:
cat / proc / sys / kernel / sysrq
If the result is 1, it should work, since that means the Kernel was compiled with the CONFIG_MAGIC_SYSRQ option. 