Cannot login from lightdm, /tmp is not writable

[Charlie Halford]

Expected: Login via lightdm should successfully create a logged in Ubuntu session.
What happened: A session is not created and I am returned to lightdm.

When I reboot my laptop, the lightdm greeter allows me to enter my password, but when I press enter, the screen goes black, and I am shortly returned to the lightdm screen again.

I changed to a new VT, logged in, and had a look at the lightdm log and the syslog. The syslog showed issues with pulseaudio writing to /tmp, and the lightdm log (possibly the xorg log) showed issues writing to /tmp as well. Looking at /tmp, I could see it was owned by root:root, and the permissions were 755.

I tried running a `chmod 777 /tmp`, then switched back to lightdm and attempted a login. This time I was successfully logged in, with no further issues. If this bug was a one off, I would just ignore it and continue on, but this permissions problem (/tmp at 755) occurs at every boot now. I'm not sure what triggered this behaviour, but it only started occurring on Saturday 12th May 2012.

Ubuntu release: 11.10
lightdm version: 1.0.6-0ubuntu1.6

ProblemType: Bug
DistroRelease: Ubuntu 11.10
Package: lightdm 1.0.6-0ubuntu1.6
ProcVersionSignature: Ubuntu 3.0.0-19.33-generic 3.0.27
Uname: Linux 3.0.0-19-generic x86_64
NonfreeKernelModules: wl fglrx
ApportVersion: 1.23-0ubuntu4
Architecture: amd64
Date: Tue May 15 09:11:07 2012
InstallationMedia: Ubuntu 11.10 "Oneiric Ocelot" - Release amd64 (20111012)
SourcePackage: lightdm
UpgradeStatus: No upgrade log present (probably fresh install)

[Sebastien Bacher (seb128)]

Thank you for your bug report, the real issue there is that your tmp permissions are broken, that's likely to create other misbehaviours, lightdm still could handle that better though...

[Charlie Halford (soupmonster)]

Thanks for the reply. Yes, I wasn't really sure if lightdm was the source of my /tmp permissions problem (actually, pretty sure it isn't), but as I had no way of tracking it down, lightdm was the first place I encountered an issue.

Are there any steps I can follow to work out why this might be happening?

[Launchpad Janitor (janitor)]

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

[SlugiusRex (slugiusrex)]

I had the problem after the upgrade from Percise to Quantal Beta1. It did not happen during the upgrade from Percise to any of the Quantal Alpha versions.

For me the GUEST account login was successful, but useless because I was unable to elevate privileges using sudo ("unable to change to sudoers gid: Operation not permitted") - so I could not troubleshoot the problem.

My work around was to create a second administrator account called 'toad2' right after the upgrade but before the required reboot. I was then able to log in using the new toad2 user account but not the original toad account created using Precise.

Oddly - when I am attempting to login - I can click on the various user accounts displayed in the Unity Greeter (lightdm) and I see the appropriate wallpapers displayed as I switch back and forth between users.

That seems like a good sign, but I still get bounced back to the Unity Greater after using the original Precise created user account.

I did notice a warning about something related to /TMP being 'missing' or 'not found' or something during the initial UBUNTU boot-up. I thought it was part of that typical 'checking disk status' routing we see from time to time. It just went away by itself.

Its strange that it would affect one user account and not the others.

This issue is discussed in the ubuntuforums (http://ubuntuforums.org/showthread.php?p=12254228#post12254228).

[Robert Ancell (robert-ancell)]

Closing assumed fixed.