The gnome session doesn't work when connected via XDMCP

[Jarek Sobiecki]

I used following setup:

1. The login screen is handled by gdm3.
2. The wayland is disabled for gdm3 and xdmcp is enabled:

[xdmcp]
# Enable XDMCP. This is important for using VNC.
Enable=true
Port=177

[daemon]
# Uncomment the line below to force the login screen to use Xorg
WaylandEnable=false

3. I'm using tigernvc server, that connects via xdmcp to the xorg and exposes me login screen (I followed: https://wiki.archlinux.org/title/TigerVNC#Running_Xvnc_with_XDMCP_for_on_demand_sessions) document for that.

That setup worked for me very well. And since some time (unfortunately I'm not able to say when), instead of GDM login screen I get black screen. I'm not able to see login screen, and nothing happens.

I tried to change gdm3 to lightdm3. This somehow improved situation. I'm able to see lightdm and login, but if I chose gnome session - screen gets all black after login. For testing, I installed openbox. Selection of openbox as session helped - I was able to use openbox normally, via tigernvc client.

I tried to check logs (using journalctl --follow) when I starting new session. I haven't found anything really weird, but this is something that I see only for "failed" remote sessions:

maj 31 16:31:25 pecet gsd-color[36841]: Przekroczono czas oczekiwania
maj 31 16:31:25 pecet gsd-color[36841]: Przekroczono czas oczekiwania
maj 31 16:31:25 pecet gsd-color[36841]: Przekroczono czas oczekiwania
maj 31 16:31:25 pecet gsd-color[36841]: Przekroczono czas oczekiwania
maj 31 16:31:25 pecet gsd-color[36841]: Przekroczono czas oczekiwania
maj 31 16:31:25 pecet gsd-color[36841]: failed to obtain org.freedesktop.color-manager.create-profile auth

(Przekroczono czas oczekiwania => The waiting time has been exceeded (timeout)

[Daniel van Vugt (vanvugt)]

Please:

1. Tell us what Ubuntu version you are using.

2. Try ShowLocalGreeter=false and if that works then this would be bug 1895420

[Jarek Sobiecki (harijari)]

1) It's 22.04.2 LTS (Linux pecet 5.15.0-73-generic #80-Ubuntu SMP Mon May 15 15:18:26 UTC 2023 x86_64 x86_64 x86_64 GNU/Linux)

2) The change didn't help. I updated config, rebooted machine, the local greeter didn't show up. I tried to connect via tigervnc, same effect (black screen).

[Jarek Sobiecki (harijari)]

The issue doesn't appear, seems fixed. Not sure when it happenend, but it works :) I haven't done anything particular to fix that.