lightdm automatically logs in after logout

[bastafidli]

Lightdm makes it impossible to logout. After I logout the lightdm logs me automatically backs in.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: lightdm 1.18.1-0ubuntu1
ProcVersionSignature: Ubuntu 4.4.0-130.156-generic 4.4.134
Uname: Linux 4.4.0-130-generic x86_64
NonfreeKernelModules: nvidia_uvm nvidia_drm nvidia_modeset nvidia
ApportVersion: 2.20.1-0ubuntu2.18
Architecture: amd64
CurrentDesktop: KDE
Date: Thu Jul 19 01:18:52 2018
InstallationDate: Installed on 2016-04-26 (814 days ago)
InstallationMedia: Ubuntu-Server 16.04 LTS "Xenial Xerus" - Release amd64 (20160420.3)
SourcePackage: lightdm
UpgradeStatus: No upgrade log present (probably fresh install)

[bastafidli (ubuntu-bastafidli)]

To add further information. This is on multiseat system. Lately (~2 weeks) the system also started misbehaving where only one of the sessions can login reliably. THe other session login doesn't affect the Enter button to submit the password and start the session

[Launchpad Janitor (janitor)]

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

[Jonas Sundman (jonas-sundman)]

After the second login, the session is not comlete, e.g. groups from pam+ldap are missing. Also the default KDE Wallet is not opened upon the first successful login. sddm works as expected.

[bastafidli (ubuntu-bastafidli)]

This defect may not be in lightdm package. I was just able to reproduce it on Ubuntu 18.04.01 distribution. Here is how I did it.

I am using 18.04.01 with KDE.
I installed the skypeforlinux package
This package had unsatisfied dependency gnome-keyring as without it skype will not log in automatically.
I installed gnome-keyring and seahorse so that I can reset the keyring.
After these three I wasn't able to logout from my KDE session as I was logged back in.
It didn't help to uninstall skypeforlinux or seahorse.
Only after I uninstalled gnome-keyring and restarted my computer I am able to normally logout from my KDE session.

On a side node now even after I log out, I can still see my session hanging around using
sudo loginctl
If I log in it till create second session as reported by the above command but at least I can logout reliably.

[Seb Bonnard (sebma)]

Hi, I have the same pb. on my ubuntu xenial,
here's what I get in the "lightdm.service" journal :

$ journalctl -au lightdm -S "2020-01-29 1:59"
-- Logs begin at lun. 2020-01-27 11:14:43 CET, end at mer. 2020-01-29 02:01:47 CET. --
janv. 29 01:59:45 sebastien-B206 lightdm[11808]: Failed to write utmpx: Permission denied
janv. 29 01:59:45 sebastien-B206 lightdm[11808]: Error writing to daemon: Bad file descriptor
janv. 29 01:59:45 sebastien-B206 lightdm[11808]: Error writing to daemon: Bad file descriptor
janv. 29 01:59:45 sebastien-B206 lightdm[11808]: Error writing to daemon: Bad file descriptor
janv. 29 01:59:45 sebastien-B206 lightdm[11808]: Failed to write utmpx: Permission denied

[Seb Bonnard (sebma)]

So I've just restarted the lightdm.service :

$ sudo service lightdm restart
$ service lightdm status
● lightdm.service - Light Display Manager
   Loaded: loaded (/lib/systemd/system/lightdm.service; enabled; vendor preset: enabled)
   Active: active (running) since Wed 2020-01-29 02:09:37 CET; 13s ago
     Docs: man:lightdm(1)
  Process: 15476 ExecStartPre=/bin/sh -c [ "$(basename $(cat /etc/X11/default-display-manager 2>/dev/null))" = "lightdm" ] (code=exited, status=0/SUCCESS)
 Main PID: 15480 (lightdm)
   CGroup: /system.slice/lightdm.service
           ├─15480 /usr/sbin/lightdm
           ├─15490 /usr/lib/xorg/Xorg -core :0 -seat seat0 -auth /var/run/lightdm/root/:0 -nolisten tcp vt7 -novtswitch
           └─15618 lightdm --session-child 12 19

Jan 29 02:09:37 sebastien-B206 systemd[1]: Starting Light Display Manager...
Jan 29 02:09:37 sebastien-B206 systemd[1]: Started Light Display Manager.
Jan 29 02:09:38 sebastien-B206 lightdm[15522]: pam_kwallet(lightdm-greeter:setcred): (null): pam_sm_setcred
Jan 29 02:09:38 sebastien-B206 lightdm[15522]: pam_kwallet5(lightdm-greeter:setcred): (null): pam_sm_setcred
Jan 29 02:09:38 sebastien-B206 lightdm[15522]: pam_unix(lightdm-greeter:session): session opened for user lightdm by (uid=0)
Jan 29 02:09:42 sebastien-B206 lightdm[15618]: pam_succeed_if(lightdm:auth): requirement "user ingroup nopasswdlogin" not met by user "sebastien"