I've installed Natty on an older Samsung desktop at work. It's a shared machine that needs no screen-locking, passwords, or anything else. (Perhaps it should have those features, but nobody would use it then.)

Anyway, after the screensaver is activated, and subsequently deactivated, the interface often (though not always) freezes. By "freeze," I mean that while the mouse pointer moves on the screen, the system (Unity, perhaps?) doesn't respond to clicks or normal keyboard input (Ctrl+Alt+F1 does work, however). Additionally, the clock in the panel stops updating and continues to display the time at which the freeze occurred (which appears to be during the time the screensaver was active). The only way I've found to recover is to issue sudo service gdm restart.

After discovering this problem, I disabled the screensaver. That seemed to cure the problem for a while, but now it's back, showing up after the monitor has gone to sleep. I thought someone had fiddled with the settings, but it's unlikely anyone would do so, and I couldn't find anything amiss.

Any idea what's causing this problem and how to fix it?

  • This question should instead be filed as a bug report, thanks! Instructions here. Feb 1, 2012 at 17:31
  • @JorgeCastro: I haven't experienced this on my machine in quite some time, so I don't have the information to file a proper bug report. I did encounter it recently on another computer I was setting up for someone, but I no longer have access to that machine, either. I've learned from experience that bug containing insufficent data rarely get fixed. Feb 2, 2012 at 16:47

1 Answer 1


Still just a work-around, but I did a kill -9 on the compiz process and the gnome-session process respawned it and after a brief wait while things were redrawn, everything carried on as before.

  • Thanks. I'll give it a try the next time a freeze occurs. Jun 15, 2011 at 8:26
  • I got a freeze today and was able to test your workaround. It worked. Of particular note: Sending SIGTERM, SIGHUP and SIGINT (signals 15, 1, and 2, respectively) all failed to kill Compiz. After those signals failed, I sent SIGKILL (9). Obviously, Compiz finally died and so was respawned. Now, to find the cause... Jun 21, 2011 at 14:23
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    What's a kill -9? Can you explain your answer please? Jul 26, 2011 at 8:42
  • I actually just searched for this answer today to remind me of how to get my session back after another freeze. :) 'kill' is described on its manual page. 9 is SIGKILL: "For other processes, it may be necessary to use the KILL (9) signal, since this signal cannot be caught."
    – torpesco
    Jul 27, 2011 at 16:09

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