Fix a Frozen System with the Magic SysRq Keys
by Jacob
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.
Stop.
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.
R-E-I-S-U-B.
