I have been trying to enable XDMCP on GDM without much success. Following some instructions I have edited /etc/gdm/custom.conf and added:
[daemon] RemoteGreeter=/usr/lib/gdm/gdm-xdmcp-chooser-slave [xdmcp] Enable=true
Then restarted gdm and tried to connect both locally and from a remote system with:
Xnest :1 -query localhost Xnest :1 -query remote_system_hostname
I just get a black screen instead of the GDM window as expected. I am missing something ?