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I am using centOS, sometimes the system just does not respond at all. In windows box, I can ctrl-alt-delete.

On a Linux machine, how should I handle this?

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What exactly do you mean by "not respond"? Can you ping it on the network? Or is it mouse input? –  Keith Apr 27 '11 at 13:52
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5 Answers 5

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IMHO, There is no such ctrl+alt+del key-combination for Linux. But to check, why the machine get hangs, you can do either:

  1. Press alt+ctrl+f1, and observe the command "top", to see "who"/"which program" is eating up the cpu and causing the hang.
  2. You can place "system-monitor" in the taskbar, whose indicator will show the cpu-usage, for observation.
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If you have a keyboard attached, you could do the RESUIB method. Otherwise try to ssh into your box, and us top, ps and the usual helper and log checker programs to hunt down your problem.

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There are the so-called "Magic SysRq keys" -- a set of keypresses that can be embedded at kernel level and will be honored as long as both the kernel process and the keyboard interrupt are still being listened to, and can be called by alt-SysRq-keypress.

These can perform various emergency tasks such as an emergency S ync of all mounted filesystems, k I lling all active tasks, or even forcing a hard re B oot.

However, linux in general needs to be pretty far gone for extreme measures like that to be the only remaining solution. Use only with extreme caution and when all else has failed.

As others have mentioned, though, "doesn't respond" is a bit vague. Can you clarify what is or isn't happening?

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I was going to answer with almost the exact same thing. –  bahamat Apr 27 '11 at 16:27
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If the problem is related to the x session (which, many are) you should be able to ctrl-alt-f1, ctrl-alt-f2, ... to get to a virtual session.

from there you can top, as suggested above, or, all else fails you can sudo reboot to (as cleanly as possible) get running again.

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On linux systems processes can be observed by using commands such as ps (try sudo ps waux to see a list with all users and full paths). Lots of programs such as top can help you sort and monitor behaviors. You can then send the system commands to control those process using there process id. For example you can use kill or killall to terminate anything on the system.

Some system monitors like my favorite htop will even allow you to attach traces to running processes to see exactly what they are up to and send them kill signals right from the observer.

There are some gui variants of these process monitors, but I have no experience with them. In Gnome you might look at system-monitor. There is also something known as Linux Process Explorer.

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