Ubuntu: Ubuntu 12.04 froze, requiring powercycle. What should I look / grep for in the logs?


This is not the first time that Ubuntu has froze. Last time, I checked 'recently updated files' in /var/log/ and /var/crash/ and the cause of the problem appeared to be 'LibreOffice'.

Now, it has happened again.

Nothing works, except the power-down button (based on previous experience). I can't even open tty's using Ctrl+Alt+F{1..6}

I have plenty of memory (7.7 GB), Ram (2 x 3.16Ghz) and hard drive space (100 GB on a 256GB SSD).

There is nothing I can do, except to shut down. The computer passed a memtest.

What should I look (grep) for in the logs?

Update: I have submitted a bug here: https://bugs.launchpad.net/ubuntu/+source/xorg/+bug/1023916/


A freeze sounds a lot like an error either in Xorg or in the kernel. Have you tried to ssh to the box? Sometimes that works even if local user interfaces are all irresponsive. A working ssh connection might be very helpful debugging this kind of issue.

From the data you provided, I'd go for the kernel log. It seems libreoffice crashed for some reason, and within a second, chrome was gone as well. So there was definitely some kind of problem at that time. Have a closer look at the log around those error lines, and see whether you can identify the first error message of that event cascade. The timestamps to the left should be useful, as any event related to the freeze should be pretty close to the two I mentioned.

Just judging from the two events included in your log, it seems likely that the libreoffice crash somehow made X unstable, causing both the UI freeze and the chrome crash. You will notice that chrome crashed in an X library.


I was running in the 'vanilla' default mode, although I do have xfce and kde installed.

A vanilla installation, to my understanding means a clean installation of a distribution. Try a clean install (as in format everything, create a new user and try again). Of course, backup your important files before doing this.

Also, instead of reinstalling, you could try creating a new user. This can pin-point the problem: If the new user works, the problem is located in your home user settings. If it doesn't, it's a system problem (and reinstalling would solve it probably)

Do not install anything else. Do not use PPAs. Only update the software through update manager or apt-get, without altering/adding the sources.list. That means vanilla installation. See how the system responds for 3-4 days. Then start adding software one-by-one in order to discover the problematic package.

After a reboot, the system usually appends a ".old" or ".0" in the filename.

I'd say these log files would be informative:

tar czf mylogs.tar.gz --ignore-failed-read ~/.xsession-errors.old /var/log/Xorg.0.log.old /var/log/dmesg.0 /var/log/syslog.1 /var/log/kern.log.1 /var/log/apport.log.1 /var/log/pm-powersave.log.1  file-roller mylogs.tar.gz  

...or if you prefer it separately:

cat ~/.xsession-errors.old  cat /var/log/Xorg.0.log.old  cat /var/log/dmesg.0  cat /var/log/syslog.1  cat /var/log/kern.log.1  cat /var/log/apport.log.1  cat /var/log/pm-powersave.log.1  


Various applications segfault and kernel oops usually are symptoms of hardware problems. Try first to run a memtest, it will probably fail with errors.

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