cannot start X session with NIS account

[Fabien]

When login with a NIS account, X does not start, or more precisely it starts and exits immediately.

Only errors in logs is:
 (EE) systemd-logind: failed to get session: PID 4335 does not belong to any known session

X11/gdm login works fine with local accounts.

SSH/terminal console login with NIS accounts works fine.

/etc/X11/Xwrapper.config:
  allowed_users=anybody

I've seen several reports of such problems under other versions (eg 19.10), but no working solutions was found. It seems that the problem is the same with lightdm.

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: gdm3 3.34.1-1ubuntu1
ProcVersionSignature: Ubuntu 5.4.0-29.33-generic 5.4.30
Uname: Linux 5.4.0-29-generic x86_64
ApportVersion: 2.20.11-0ubuntu27.2
Architecture: amd64
CasperMD5CheckResult: skip
CurrentDesktop: ubuntu:GNOME
Date: Thu Jun 4 08:59:25 2020
InstallationDate: Installed on 2019-11-26 (190 days ago)
InstallationMedia: Ubuntu 19.10 "Eoan Ermine" - Release amd64 (20191017)
SourcePackage: gdm3
UpgradeStatus: Upgraded to focal on 2020-04-24 (40 days ago)

[Sebastien Bacher (seb128)]

the issue seems to be a systemd on

 (EE) systemd-logind: failed to get session: PID 4335 does not belong to any known session

[Launchpad Janitor (janitor)]

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

[Balint Reczey (rbalint)]

Do you seem to observe https://github.com/systemd/systemd/issues/2941 ?

[Sebastien Bacher (seb128)]

summary from the upstream bug referenced

'It turns out I had /proc mounted with hidepid=2 (turning this off fixes the problem) and systemd-logind was unable to read /proc/$PID/cgroup'

[Ketiw Simplistic (ketiwsim)]

I have the same problem on 20.04 but initial error is:
gdm-password][2057]: pam_systemd(gdm-password:session): Failed to create session: Invalid argument

lightdm in kde or xfce works fine and user can login from terminal.

[Ketiw Simplistic (ketiwsim)]

This is a very serious bug. I tested with couple computers to which only addition after standard installation was NIS and NFS and the error is always there. Local users can login to gdm3 session but NIS users cannot and the error is always the same. If this is a single issue I could live with it replacing gdm3 with lightdm but I am sure this will create other problems and I also found that the NIS users cannot open teamviewer session.

[Fabien (w-launchpad-net-coelho-net)]

> Do you seem to observe https://github.com/systemd/systemd/issues/2941 ?

The message is the same, but I cannot see a "hidepid" mount option anywhere.

As a standard user I can see all /proc/<number> directories, and read the /proc/<n>/cgroup file of other users, including root.

So I'd say that it is not exactly the same issue.

[Ketiw Simplistic (ketiwsim)]

Similarly here this is not the hidepid problem: mount returns:
proc on /proc type proc (rw,nosuid,nodev,noexec,relatime)

[Pavel Riha (trilogic)]

same problem here.
problem solved by switch to LightDM
so I'm not sure that it is systemd fault

[Balint Reczey (rbalint)]

Since lightdm works OK there is most likely something that GDM could do differently.

I think this is a duplicate of LP: #1745664 . Does installing ncsd resolve the issue with gdm3, too?

[Pavel Riha (trilogic)]

altough LightDM solve the login problem, it's not solution, becouse the NIS user can not shutdown/reboot the computer from the gnome session.

so I switch back to gdm and try the nscd hint .. looks like this solve both problem for me!

[Nick Rosbrook (enr0n)]

Marking invalid for systemd due to age, and it being unclear whether this is in fact a systemd bug.