Linux remote desktop from GDM
For quite some time I have wanted to be able to create thin linux workstations that automatically connect to a remote display manager of some kind for the relevant desktop services. This has always been somewhat of a mystery to me, but I found the final answer to be quite simple.
First, you need a system like a windows Remote Desktop server, or xrdp server configured. Make sure that you can connect and login to it.
Now install your thin client. I used CentOS with a minimal desktop install to give me an X server.
Install the "rdesktop" package on your thin client.
Now you need to add the Remote Desktop session type.
Create the file "/usr/bin/rdesktop-session" (Or /opt or /srv. Up to you - but make sure it's executable)
#!/bin/bash
/usr/bin/rdesktop -d domain.example.com -b -a 32 -x lan -f termserv.example.com
Now you need to create a session type that GDM will recognise. Put this into "/usr/share/xsessions/rdesktop.desktop". These options could be improved etc.
[Desktop Entry]
Name=RDesktop
Comment=This session logs you into RDesktop
Exec=/usr/bin/rdesktop-session
TryExec=/usr/bin/rdesktop-session
Terminal=True
Type=Application
[Window Manager]
SessionManaged=true
Create a user who will automatically connect to the TS.
useradd remote_login
Configure GDM to automatically login after a time delay. The reason for the time delay, is so that after the rdesktop session is over, at the GDM display, a staff member can shutdown the thin client.
[daemon]
TimedLoginEnable=True
TimedLogin=remote_login
TimedLoginDelay=15
Finally, set the remote login user's session to RDesktop "/home/remote_login/.dmrc"
[Desktop]
Session=rdesktop
And that's it!
If you are using windows terminal services, you will notice that the login times out after about a minute, GDM will reset, wait 15 seconds and connect again, causing a loop of this action. To prevent this, you should extend the windows server login timeout. On the terminal server:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Terminal Server\WinStations\[[Connection endpoint]]\LogonTimeout (DWord, seconds for timeout)
[[Connection endpoint]] is the name in RD Session Host configurations : I had rebuilt mine as default and was wondering why this no longer worked. This way you can apply the logon timeout to different session connections.
Update: Actually, it needs to be RDP-Tcp regardless of the connection endpoint. Bit silly.