Ask Ubuntu is a question and answer site for Ubuntu users and developers. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I have recently installed new system on my disc, Ubuntu 12.04. Installation proceeded without problems, I started installing additional software and put data from other discs. I had already two times bug report, it was quite long, and I have no idea how to acces to log file (which probably is somewhere saved) and since I had to switch off the computer using the button, anything else was possible, here is just a small part of it (what I've noted on paper)

could not write bytes: Broken pipe

speach dicpatcher disabled: edit etc/default/speach-dispatcher

saned disabled: edit ....

and than:

BUG: unable to handle kernel NULL pointer dereference at 0000009c

I've run Memory test in GRUB, everything is fine.

First time it occured when I was using rsync, second time when I was trying to install texlive.

Should I install whole system once again? Or can it be hardware problem? Or something else?

If there is any hardware details which may be relevant, please ask, since I have no idea what is happening, I don't know what kind of information could be useful.



dmesg output:

share|improve this question
up vote 1 down vote accepted

A NULL pointer deference error is from the kernel and it is highly likely to be a kernel bug, there is no need to re-install. It is hard to answer this question as there is not enough information. The kernel will emit a lot of debug information that helps kernel developers to determine what is causing this problem. This information appears on the console (you can switch to that using CtrlAltF1 and back again using CtrlAltF7, or the command:


should show the full message.

share|improve this answer
Thanks for reply. I had to switch off the computer (maybe I could press ctrl+Alt+F7 but I didn't knew) so when I go to F1, there is nothing now. I have run -dmesg, it's very long and it's not what has appeard before. I'll try to post it in the body of queston, I don't know if it's not too long. – maria Nov 16 '12 at 22:15
I don't know how to do it. The output has more than thousand lines... Any advice? – maria Nov 16 '12 at 22:20
OK, so next time you see that message I suggest filing a bug and getting a kernel team engineer to look at it. As it is, there weren't any offending NULL pointer deference bugs in that log you posted, so it's hard to tell. A NULL pointer deference basically means that the kernel tried to read or write to some memory that was pointed to by a pointer which was NULL. Since memory access was offset from zero we can assume it was the kernel trying to access an element of data in some data structure. But we need more info to debug this further. – Colin Ian King Nov 16 '12 at 23:15
Ok, no problem, but could you tell me what should I do if it happens nex time? I try to get back to "normal" window (F7) and than send the output of dmesg command? How should I "get a kernel team engineer to look at it? I suppose not by posting here again? Thanks a lot. – maria Nov 16 '12 at 23:23
If it happens next time, open up a terminal using Ctrl-Alt-t and then type: dmesg > Desktop/dmesg.log and then submit a bug using apport-bug linux and then attach the dmesg.log from your Desktop to the bug report. – Colin Ian King Nov 17 '12 at 21:31

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.