How to Access Entire Desktop Remotely in Linux

There is no doubt that running X applications remotely is useful, but a truly killer feature is the ability to run the entire desktop from a remote computer on your local machine.
To do this, you need to use a feature called the X Display Manager Control Protocol (XDMCP), which is part of X. This protocol allows remote computers to access the GDM/KDM/XDM login program, which then gives access to the remote desktop. If you have a reasonably fast network connection—Ethernet speeds of 10-Mbit or greater are recommended—it is possible for a slow computer to be as responsive as a cutting-edge machine.This is possible because the local box is just a display device, like a television, and all the real work is done on the faster remote machine.

To use XDMCP, you must be running XDM, GDM, or KDM as your login manager on the remote machine. Each display manager has support for XDMCP, and you must turn on that support.

To enable XDMCP in GDM, you need to load the gdmconfig tool. Inside this tool is an XDMCP tab. Turn on XDMCP support by setting the Enable XDMCP option. You can use some additional settings on this tab to fine-tune XDMCP support. After you've made your changes, you must restart GDM.

There is no GUI way to turn on XDMCP in KDM, so you need to edit the kdmrc file on your system. Both a system-wide file (possibly in /etc/kde3/) and a per-user file (in ~/.kde/share/config) exist. Inside kdmrc is an [Xdmcp] section where you need to set the Enable option to true. After you save this change, you must restart KDM.

When you have turned on this support, you can return to your local machine and search the network for computers that are allowing XDMCP connections. To do this, ensure that you are logged out of X and run the following command:

foo@bar:~$ X -broadcast

X will start and the login screen from the remote machine will appear. Now you can log in and use the machine in the same way as if you were sitting in front of it. If you want to connect to a specific machine on the network, you can also run the following command on your local machine (remember to change the IP address to a host that is relevant to your network):

foo@bar:~$ X -query
192.68.0.2