REISUB Performs a Safe Reboot of a Linux Computer

By Nicholas Scribner
March 28, 2021

Tonight, I was writing an email to my brother, when suddenly my computer locked up. Not wanting to lose the contents of my email, I took out my iPhone to look up how to do the equivalent of Control-Alt-Delete on Ubuntu Linux — a familiar search query for me, though I'd never had success in the past. This time, however, I found an informative forum post on Ask Ubuntu as the first result. The most useful answer instructs the user to first try a few other methods when the computer hangs. None of these methods worked for me (no surprise, as they never had in the past). But the last method sounded promising because it didn't sound familiar. It promised a safe reboot without having to press and hold the power button — a big no-no among computer people — and involved pressing an interesting sequence of keys (someone commented that "REISUB" is "BUSIER" backwards).

Here are the instructions: Press and hold Alt + SysRq. If your keyboard doesn't have a SysRq key, press PrtScr instead. While holding the previous keys, press, in order, R, E, I, S, U, B while making sure to pause for one second between each key, since "each letter is a different kernel action leading to a 'graceful' reset."

After following the above instructions, my computer rebooted like magic. Note that my ThinkPad doesn't have a SysRq key, so I pressed PrtSc (the screenshot key) instead. Furthermore, I don't like trying things on computers based on one forum post (however credible), so I Googled this method before trying it and read this helpful article that confirmed the above answer and recommended a Wikipedia article on the topic.

Back to that email I was writing to my brother, the contents reappeared in my webmail in Firefox after the reboot. So it all worked out.

Article ID: 6