Unity/LightDM session crashes - login screen appears

[Dariusz Gadomski]

Almost each time I login to Unity using LightDM after some time (from 5 min to about 2-3 hours) my session crashes and I am taken to the login lightdm screen again. It does not matter what applications are running - sometimes I get it when I have only the browser running, sometimes during playing a video and sometimes when doing something in Eclipse.

It started about 2-3 weeks ago.

The only trace in the logs I was able to find is:
[+1980.37s] DEBUG: Process 1391 exited with return value 1
[+1980.37s] DEBUG: X server stopped
[+1980.37s] DEBUG: Removing X server authority /var/run/lightdm/root/:0
[+1980.37s] DEBUG: Releasing VT 7
[+1980.37s] DEBUG: Display server stopped
[+1980.37s] DEBUG: Stopping display
[+1980.37s] DEBUG: Session 2068: Sending SIGTERM
[+1980.49s] DEBUG: Session 2068 exited with return value 0
[+1980.49s] DEBUG: User session quit
[+1980.49s] DEBUG: Display stopped
[+1980.49s] DEBUG: Active display stopped, switching to greeter
[+1980.49s] DEBUG: Switching to greeter
[+1980.49s] DEBUG: Starting new display for greeter
[+1980.49s] DEBUG: Starting local X display
[+1980.49s] DEBUG: Using VT 7
[+1980.49s] DEBUG: Logging to /var/log/lightdm/x-0.log
[+1980.49s] DEBUG: Writing X server authority to /var/run/lightdm/root/:0
[+1980.49s] DEBUG: Launching X Server
[+1980.49s] DEBUG: Launching process 7495: /usr/bin/X :0 -auth /var/run/lightdm/root/:0 -nolisten tcp vt7 -novtswitch
[+1980.49s] DEBUG: Waiting for ready signal from X server :0
[+1980.78s] DEBUG: Got signal 10 from process 7495
[+1980.78s] DEBUG: Got signal from X server :0
[+1980.78s] DEBUG: Connecting to XServer :0
[+1980.78s] DEBUG: Starting greeter

Unfortunately I was not able what was process 1391 in that case. Maybe the attached logs will help you discover it.

I am able to reproduce it so if you need any additional logs I should be able to get them right after the next crash.

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: lightdm 1.2.1-0ubuntu1.1
ProcVersionSignature: Ubuntu 3.2.0-29.46-generic 3.2.24
Uname: Linux 3.2.0-29-generic x86_64
NonfreeKernelModules: nvidia
ApportVersion: 2.0.1-0ubuntu12
Architecture: amd64
Date: Tue Jul 31 16:39:40 2012
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Beta amd64 (20120328)
ProcEnviron:
 TERM=xterm
 PATH=(custom, user)
 LANG=pl_PL.UTF-8
 SHELL=/bin/bash
SourcePackage: lightdm
UpgradeStatus: No upgrade log present (probably fresh install)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Dariusz Gadomski (dgadomski)]

After it happened again I was able to observe that the process which exited was /usr/bin/X.

[John S. Gruber (jsjgruber)]

I suggest that you attach the last several Xorg.n.log's from /var/log in order to look for why the X server would have crashed.