From a fresh debian xdm install: files in /etc/X11/xdm - add a "*" to Xaccess so any host can get a login window - comment out "! DisplayManager.requestPort: 0" in xdm-cofnig - in Xservers I disabled the entry for :0 since I'm not running it on my local display. It work, then it doesnt! Crap software.. Apparently xdm.pid doesn't get created. And now it works again. Hmm..