Documented at <https://wiki.ubuntu.com/LucidLynx/ReleaseNotes#GDM%20does%20not%20support%20XDMCP>:
The version of gdm included in Ubuntu 10.04 LTS does not support the XDMCP protocol for remote graphical logins. Users who require XDMCP support will need to install another display manager, such as wdm or xdm, for this functionality. (408417)
Documented at <https:/ /wiki.ubuntu. com/LucidLynx/ ReleaseNotes# GDM%20does% 20not%20support %20XDMCP>:
The version of gdm included in Ubuntu 10.04 LTS does not support the XDMCP protocol for remote graphical logins. Users who require XDMCP support will need to install another display manager, such as wdm or xdm, for this functionality. (408417)