Fix a Frozen System with the Magic SysRq Keys
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.
- Hold down the Alt and SysRq (Print Screen) keys.
- While holding those down, type the following in order. Nothing will appear to happen until the last letter is pressed: REISUB
- 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.