Since a recent upgrade from 10.04 LTS to 12.04 LTS I can no longer login using XDMCP (ssh -XC is okay).
This is similar to an earlier question but the answer (add xserver-allow-tcp=true) didn't help me.
I have followed the instruction to setup LightDM as an XDMCP server as follows:
[SeatDefaults] user-session=ubuntu greeter-session=unity-greeter xserver-allow-tcp=true [XDMCPServer] enabled=true
And then restarted by
sudo restart lightdm
I have the following in /var/log/lightdm.log
[+0.01s] DEBUG: Waiting for ready signal from X server :0 [+0.01s] DEBUG: Starting XDMCP server on UDP/IP port 177 [+0.01s] DEBUG: Acquired bus name org.freedesktop.DisplayManager [+0.01s] DEBUG: Registering seat with bus path /org/freedesktop/DisplayManager/Seat0 [+0.18s] DEBUG: Got signal 10 from process 4925 [+0.18s] DEBUG: Got signal from X server :0 [+0.18s] DEBUG: Connecting to XServer :0
netstat -l | grep xdmcp gives
udp 0 0 *:xdmcp *:* udp6 0 0 [::]:xdmcp [::]:*
which seems okay (although others had said there should be a TCP port 6000 here as well).
The firewall port is open:
sudo ufw status
177 ALLOW Anywhere 6000 ALLOW Anywhere 22 ALLOW Anywhere (v6) 177 ALLOW Anywhere (v6)
But no go:
Xephyr :2 -query *
[dix] Could not init font path element /usr/share/fonts/X11/cyrillic, removing from list! [dix] Could not init font path element /usr/share/fonts/X11/100dpi/:unscaled, removing from list! [dix] Could not init font path element /usr/share/fonts/X11/75dpi/:unscaled, removing from list! [dix] Could not init font path element /usr/share/fonts/X11/100dpi, removing from list! [dix] Could not init font path element /usr/share/fonts/X11/75dpi, removing from list! XDM: too many retransmissions, declaring session dead
Does anyone have any clues, or even how I can go about debugging this?