Otherwise entitled.... "You learn a new thing every day"
(oh, and Windows users don't bother reading any further....
)
So there was I happily doing a remote firmware upgrade of a machine having booted off the manufacturer's Linux based CD tool.
All went ok....all the various bits of firmware updated and I was prompted to hit the GUI button entitled "restart now".
The GUI promptly exited, but instead of seeing a reboot, I was left with a black screen with nothing else but the X11 mouse cursor.
Tried the usual Ctrl+Alt+F1(-F6) tricks to switch between X11 and console etc, but nothing.....
I had the luxury option of remote control power switching.... but that sort of thing is a bit dangerous to do during the day incase you switch the wrong supply.
Then Mr Google decided to educate me in the beauty that is the Magic SysRQ key.
One 'Ctrl'+'Alt'+'SysRq'+b later and the system obediently and immediately rebooted itself.
See the Wiki entry
here for more info on this cool and powerful command....who needs ctrl alt delete !
Hopefully you'll never have to use the command in anger, but if you do, you'll be glad you knew about it !