How To Force Reboot A Frozen Ubuntu Safely

(Well, technically, this technique should work on most, if not all, Linux distros.)

What to do when your Ubuntu crashes or freezes? We all have encountered this before for no apparent reason. Either it does not reach the desktop and you are left staring at a black screen or a pretty wallpaper. Another not so apparent reason might be the result of installing that new graphics driver or simply an unstable system app. It could be the kernel after you upgraded to a higher version.

In moments like this there are several things to do without hitting the power button. And there is good reason why you should not hit that button or pull the power chord. The disk might get damaged if it is still being written to. So never hit that button unless Linus Torvalds himself tells you to do otherwise.

  1. Try going to another terminal. Press ALT + F2 or CTRL + ALT + F2, where if you are lucky, you’ll get a login prompt. Reboot using `sudo reboot` or the longer way with `sudo shutdown -r now`.
  2. Kill the X server with the CTRL + ALT + Backspace combo. This does not seem to work anymore, but I figure it was worth mentioning here.
  3. Three Finger Salute. This is the CTRL + ALT + DEL (Delete) key combo. Perhaps the most popular way to reboot after everything goes haywire. This usually works, but there are those crashes where it does not do the trick.
  4. If #3 does not work you can do a Magic SysRq key(s). In case you are wondering, the SysRq key is also the Print Screen (PrtScr). Description on how to do this command follows.

Finally, when everything else fails, the Magic SysRq key(s) or ALT + SysRq + K for the Linux kernel. No you do not have to go wave a wand and yell a silly spell like Harry Potter. What is it then?

Press and hold CTRL + ALT, tap SysRq, then key in the following letters in order R E I S U B.

R E I S U B is BUSIER spelled backwards. That will help you remember. You can go on and assign a mnemonic to the letters as a memory aid.

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Notice: This article was published on August 20, 2011 and the content above may be out of date.