Ubuntu – (closed) Configuring and using Xdmcp with gdm3 on ubuntu 18.04

18.04gdmxdmcp

On a fresh minimal ubuntu 18.04 installation, I tried to activate and use the gdm3 xdmcp server.

Here are steps I followed:

  • Installation

I used the normal installation.

"Download updates during installation" was checked

"Install 3rd parties for Gfx/Wifi/.." was not checked.

  • Xdmcp server

1 . Edit /etc/hosts.allow to set (cf. Gnome doc.).

ALL: ALL #Wide opened to be sure the problem isn't here

2 . Edit /etc/gdm3/custom.conf to set:

[security]
DisallowTCP=false
[xdmcp]
Enable=true

3 . Restart gdm

sudo /etc/init.d/gdm3 restart

  • Xdmcp client

sudo apt install xnest
Xnest -query localhost -geometry 1024x768 :1

Unfortunately, I only have a black screen with regular white flash.

Where did I do something wrong ?

Thanks for your help.

Christophe C.

Best Answer

In case soemone else finds this question and has problems getting XDMCP to work with gdm3, I managed to get it working by setting gdm3 to use xorg instead of wayland.

/etc/gdm3/custom.conf

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