I sometimes experience whole Ubuntu freezes (from 14.04 to 16.04, I upgrade by a clean installation), just mouse can move (that's why this question is different from others). I think this is caused by one of the cores stop working when 100% load by unresponsive Desktop Environment. There isn't any magic key combination like Ctrl+Alt+Del or Ctrl+Shift+Esc known from Windows. The only thing I could do is hold power button for 5-10 seconds and hard shut down. Is there any other recommended solution?

Could I e.g. with some keyword combination reset CPU or kill all additional services or reset Unity or force soft reboot or I don't know what else could help?

  • 2
    Can you access another tty? Ctrl + Alt + F1 (changing F1 to F1-F6 to access the terminal that you want)
    – user508889
    Jun 6, 2016 at 13:20
  • @bc2946088 I'll try next time
    – aleskva
    Jun 6, 2016 at 13:23
  • @Parto I ask about killing unresponsive OS (or Desktop Environment), not application
    – aleskva
    Jun 6, 2016 at 13:25
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    I don't think it's a duplicate, atleast of that link @Parto. They're talking about individual applications within Unity they want to stop. Not when Unity itself goes unresponsive.
    – user508889
    Jun 6, 2016 at 13:25
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    The reason this is a duplicate is because the mouse moving is a red herring. It just means you have hardware cursor support, which means mouse movement bypasses the OS entirely.
    – rich remer
    Jun 7, 2016 at 4:34

2 Answers 2


Well there is a magic key combination (to reboot):

While holding Alt and the SysReq (Print Screen) keys, type REISUB

For more details visit this answer : https://askubuntu.com/a/36717/497359

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    ConflictBoy solution is preferrable if it works. Also I believe it's possible to disable kernel's "magic keys", in which case this wont work.
    – Bakuriu
    Jun 6, 2016 at 17:05
  • @Bakuriu Yes, I just posted this answer as the Op was asking "magic key combination" similar to ctrl+alt+del in his question, ConflitBoy solution is preferable indeed. Jun 6, 2016 at 17:09
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    @Bakuriu: Ubuntu disables many of the magic sysrq key combos by default (like Memory, Processes, and other info dumps). At least Umount, Sync, and reBoot are left enabled in a default install, though. (I use them in that order when things are totally locked and I can't get in with ssh or a text console. remount-ro implies any necessary syncing, and then sync after the filesystems are already read-only makes sure that nothing can be dirtied between then and reBoot.) If you've had bad USB hardware, then it's easy to form a mental association between computer crapping out and typing USB :P Jun 8, 2016 at 7:53
  • I have got those separate, so SysReq or Print Screen? And I can use them only with fn key pressed, will this work too?
    – aleskva
    Jun 22, 2016 at 2:07
  • okay, I googled out it is SysReq and it will work with fn too
    – aleskva
    Jun 22, 2016 at 2:08

Switch to the console: CTRL + ALT + F1

After login, you can see which processes are running using this command:

ps -ef

If you see a process which has high CPU usage, you can kill it.

sudo kill <pid>

Of course, you can simply restart the PC too:

sudo reboot
  • 4
    In case ctrl+alt+f1 does not work, it is worth trying with an ssh client instead.
    – kasperd
    Jun 6, 2016 at 19:32
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    As an alternative to ps -ef you could also try "top" and/or "sudo iotop".
    – aap
    Jun 6, 2016 at 22:37
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    For some reason, only Ctrl+Alt+F3 works and F1 to bring up the console. Jun 2, 2018 at 16:39
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    This brings a black screen but it seems to freeze on that when I try it
    – Daveguy
    Jul 13, 2021 at 21:02
  • After Ctrl + Alt+ F1, screen turns black. That's it nothing else Sep 18, 2021 at 10:20

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