REISUB - How to Reboot a Frozen System
Came across this when looking through the PCLinuxOS forums -http://fosswire.com/2007/09/08/fix-a-fr ... ysrq-keys/
Quote from the site:-
You finally got your Linux environment to crash. Ctrl+Alt+Backspace does nothing, nor do the F-keys. You know you shouldn’t have installed that bad driver, but you did it anyway.
So you reach for the power button.
Mashing in the power button to reboot could cause a problem if your hard drive is still being written to, and usually causes more problems than it solves. The Linux kernel includes a secret method of restarting your PC should it ever stop doing its job.
1. Hold down the Alt and SysRq (Print Screen) keys.
2. While holding those down, type the following in order. Nothing will appear to happen until the last letter is pressed: REISUB
3. Watch your computer reboot magically.
What the individual keys do in that sequence are not as important as what it does as a whole: stops all programs, unmounts all drives, and reboots. A lot safer than just cutting the power.
Here it is again: REISUB. Remember that, as it will save you a lot of time when you are configuring a system and something gets messed up. Need a mnemonic? Try Raising Elephants Is So Utterly Boring.
As an aside, don’t try this if you just want to reboot. A normal reboot, if it can be done, should always be used instead of the REISUB keys.
Good tip yes, ..... but not really new. It's a very old trick in fact. But it probably can't harm to repeat those things from time to time so others get a chance to see this too.
And just to make sure everyone understands this:
This is for emergencies only, e.g. when the system absolutely locks up + freezes. This is not to be used on potentially still busy machines (e.g. which are still writing stuff to disk) or on machines that could still do a proper shutdown if you only were patient enough to wait. This is only for systems which have already died a horrible death, e.g. power-cycling them is the only way to get them back to life ..... *Then* and only then you may try your luck and use this.
Besides, I am not really sure this works on Ubuntu-based distros ... I read somewhere that they disabled this per default