The relevant lines fromt the LightdmLog.txt file which is attached above are:
[+135.46s] DEBUG: Closing guest account guest-2kgkn2 with command '/usr/sbin/guest-account remove guest-2kgkn2' [+135.67s] DEBUG: Guest account cleanup script returns 2048 [+135.87s] DEBUG: Seat seat0 changes active session to [+135.87s] CRITICAL: session_get_login1_session_id: assertion 'session != NULL' failed -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to lightdm in Ubuntu. https://bugs.launchpad.net/bugs/1559513 Title: passwd and group entries are not removed on logout from a guest session Edit Status in lightdm package in Ubuntu: New Bug description: See bug #1556516 for details and a patch file to fix the problem. I filed that directly, before I discovered ubuntu-bug. This bug occurs for me using the mate desktop. ProblemType: Bug DistroRelease: Ubuntu 16.04 Package: lightdm 1.17.6-0ubuntu1 ProcVersionSignature: Ubuntu 4.4.0-12.28-generic 4.4.4 Uname: Linux 4.4.0-12-generic x86_64 NonfreeKernelModules: nvidia_uvm nvidia_modeset nvidia ApportVersion: 2.20-0ubuntu3 Architecture: amd64 CurrentDesktop: MATE Date: Sat Mar 19 12:31:19 2016 InstallationDate: Installed on 2016-03-08 (11 days ago) InstallationMedia: Ubuntu-MATE 16.04 LTS "Xenial Xerus" - Alpha amd64 (20160224) SourcePackage: lightdm UpgradeStatus: No upgrade log present (probably fresh install) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/lightdm/+bug/1559513/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp
