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This page intends to allow remote sessions using "X Display Manager Control Protocol" (XDMCP). See the GDM documention for more information on the parameters: https://help.gnome.org/admin/gdm/3.26/gdm.html#xdmcpsection.

Setup Graphical Logins


Modify /etc/X11/xdm/xdm-config and comment out:

DisplayManager.requestPort:    0

So it will be:

!DisplayManager.requestPort:    0

Then modify /etc/X11/xdm/Xaccess to allow any host to get a login window. Look for a line that looks like this:

*             #any host can get a login window

and remove the hash '#' sign at the beginning of the line.

In case you have multiple network interfaces also add a line like this:


Where should be you server IP address.

Then reboot or restart your X server and xdm daemon.


Modify /etc/gdm/custom.conf to include:


Then restart the Gnome Display Manager:

systemctl restart gdm

Or if using the inittab method, login as root on another tty and

telinit 3
telinit 5 && exit 


Support for this feature seems to be very buggy. Lightdm is probably an easier choice.

Edit kdmrc ( /opt/kde/share/config/kdm/kdmrc [KDE 3x] or /usr/share/config/kdm/kdmrc (KDE 4x] ) and at the end there should be something like this:


Then you need to restart your X server so the change you just made takes effect:

systemctl restart kdm


Modify /etc/lightdm/lightdm.conf

Enable the XDMCP Server:


On a headless system, disable the automatic start of one seat so that LightDM can run in the background:


Then restart the LightDM:

systemctl restart lightdm

Accessing X from a remote Machine on your LAN

You can access your login manager on the network computer via the following command. TCP and UDP streams are opened. So it is not possible to access the login manager via an SSH connection.

Xnest -query -geometry 1280x1024 :1

Or, with Xephyr, if you experience refreshing problems with Xnest:

Xephyr -query -screen 1280x1024 -br -reset -terminate :1

Or, if you are on runlevel 3

X -query your_server_ip

Xserver should recognize your monitor and set appropriate resolution.

Note: You can enable XDMCP Direct/Query and Broadcast connections from remote hosts without XDM starting a local X server.

After allowing XDMCP access as described above, edit /etc/X11/xdm/Xservers and comment out:

#:0 local /usr/bin/X :0

Then launch XDM as root, e.g. xdm -config /etc/X11/xdm/archlinux/xdm-config

Thin client setup

First of all one should setup dhcp and tftp server. Dnsmasq has both of them. For network boot image check thinstation project. If your network card does not support PXE, you can try Etherboot

Example GUI-based Clients


Session declined: Maximum Number of Sessions Reached

Edit /etc/gdm/custom.conf and add/increase the maximum sessions.


Login screen and GNOME is somehow flickering

If the login screen is created again and again and unresponsive, you are trying to access GNOME Shell on the remote machine. This is apparently caused by network speed, e.g. by accessing via wireless connections. The workaround is to disable/deinstall GNOME Shell.

 pacman -R gnome-shell