Problems with gdm but not with lightdm

[LE MIEUX]

Hi,
In the same room :

• 13 PC Debian Buster with GDM (Gnome Display Manager)
• 8 old PC with Debian Buster with LightDM
  The master is one of the 13
  The master can see the 8 ones but none of the 12.
  Could it be related with the display manager ?
  (I've installed manually the latest version 4.5.6-0 : the oldest 4.1 used to be OK until some months (may be after an update of the Debian distribution)

Thanks,
Vincent Le Mieux

[tobydox]

Likely this is related to Wayland instead of X11 being used by GDM (while LightDM always uses X11). Veyon currently only supports X11 so you should try the configuration change suggested at https://unix.stackexchange.com/a/336227

[LE MIEUX]

Hi,

Thanks for your answer.
I've changed the /etc/gdm3/daemon.conf : uncomment the "#WaylandEnable=false" line. I've also tried to start the session by manually choosing an Xorg session but the problem is the same :
On this screenshot :

• the left and right columns : the PCs with Debian Buster and GDM ; the master is the same model.
• the two colums in the middle, the old laptop PCs with Debian Buster and lighDM

Five PC where started :

• the master can see the two laptops (one with a started session, the other one waiting for a session login)
• the master can't see the 3 others.

On the laptops the command "telnet localhost 11100" is OK but not with the 3 others. For those ones the ping with the master is however OK.

An idea ?

Best regards
V.Le Mieux

[LE MIEUX]

Hi,
The way to fix this problem :

• install the lightdm package on the PC running gdm
• select lightdm option during installation
• reboot

Juste one question :
For which reason does the command "telnet localhost 11100" is OK just after the lightdm installation and not before with GDM ???

V.Le Mieux