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I used to be a Windows user, and when my computer froze I could press CTRL+ALT+Delete and it would restart the computer. Is there a similar function for my current operating system? Thanks everyone.

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up vote 4 down vote accepted

Ctrl+Alt+Print Screen+R,E,I,S,U,B (Hold down Ctrl, Alt, and Prnt Scrn then press REISUB in that order with about a second pause between each letter)

This is a functionality that is a part of the Linux kernel (not just Ubuntu). The only catch is that you have to have the keyboard plugged into the computer (doesn't work remotely).

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Press the power button on your keyboard. The system will allow you to select the icon that looks like a power button to turn off the computer. There's a circular arrow that will let you reboot it without powering it down, coming the closest to Windows CTRL-ALT-DELETE.

dash-plus-java's helpful suggestion is good in emergencies when this won't work, but it doesn't allow the various daemon's in your system to terminate normally. (That's not normally a disaster, though).

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@dash-plus-java answered correctly, but not all SysRq keys are enabled by default. Out of the REISUB only U and B are enabled. If you want to enable all SysRqs, do:

echo 1 > /proc/sys/kernel/sysrq

This will enable all sysrqs. If you want just some of them, change the value you echo above, as mentioned in the kernel Docs,

Now you can press and hold <Alt> <Sys Rq>, and sequentially press R, E, I, S, U and B. Each of them have specific meaning:

  • r - Puts the keyboard into raw mode, taking control of it away from the X server.
  • e - Sends the terminate signal to all processes, asking them to end gracefully.
  • i - Sends the kill signal to all processes, forcing them to end immediately.
  • s - Flushes data from your cache to disk.
  • u - Remounts all file systems read-only.
  • b - Reboots your computer.

More SysRqs:

  • n - Resets the nice level (priority) of all high and realtime priority processes.
  • f - Calls oom_kill, which will kill a memory-hogging process.
  • k - k – Kills all programs on the current virtual console, including X
  • o - Shuts off the computer.
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