kdm with no local X starting

[n dhert]

When starting /usr/local/bin/kdm (e.g. from /etc/ttys), this starts kdm-bin
(KDM window manager)
but also a local X server.
On a server machine this often is not needed.
How to configure xdm to not start a local X server?
So far I came up only with
# vi /usr/local/share/config/kdm/kdmrc
ServerCmd=""
(instead of ServerCmd=/usr/local/bin/X -br)

but there are probably more clean ways ?