Suppose you want to make a lab full of X terminals that all connect
to one main server.  So let's call one X terminal
xterminal and lets call the server
appserver.  You install GDM on both.
On appserver you enable XDMCP, so you have
[xdmcp]
Enable=true
If you want no local screens here, you can then
make the [servers] section empty.
On the xterminal you disable XDMCP (you don't
want anyone to connect to the xterminal really).  You will add a
server type perhaps called Terminal as follows:
[server-Terminal]
name=Terminal server
command=/usr/X11R6/bin/X -terminate
flexible=false
handled=false
This definition should in fact be included in the standard
configuration file.  Notice that we made the
handled key false since we don't want GDM to
handle this server localy.  Also note that we have not yet added the
-query argument, you can add that here, or in the
[servers] section.  We'll define our local
servers as follows:
[servers]
0=Terminal -query appserver
This will run a direct XDMCP query to the server named
appserver.
