How to close down GNU/Linux safely after a system freeze with the SysRq key
Despite jeering at Windows for the infamous system freezes and blue screens of death, there are and will be times when your Linux computer just locks up: the cursor is frozen and even invoking a console by Ctrl + Alt + [F2, F3, ...] to close down the X windows session running on F7 is non-functional.
This tip may be of assistance to those whose entire system has frozen and aren’t happy to just do a hard power off and trust to luck that data will not be corrupted. Fortunately GNU/Linux has journalled filesystems so the chances of this happening are reduced and you will not suffer the indignity of being told that you performed an illegal operation or having to drum your fingers waiting impatiently for scandisk to complete.
Like Ctrl + Alt + Delete this tip is a three fingered Vulcan neck pinch. It consists of Alt + SysRq and a selection of one other key (of which there are thirteen!), the choice of which will determine what operation is performed.