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24.3. Problems After Installation

24.3.1. Remote Graphical Desktops and XDMCP

If you have installed the X Window System and would like to log in to your Red Hat Enterprise Linux system using a graphical login manager, enable the X Display Manager Control Protocol (XDMCP). This protocol allows users to remotely log in to a desktop environment from any X Window System compatible client (such as a network-connected workstation or X11 terminal).
To enable remote login using XDMCP, edit the /etc/gdm/custom.conf file on the Red Hat Enterprise Linux system with a text editor such as vi or nano. In the [xdcmp] section, add the line Enable=true, save the file, and exit the text editor.
To enable this change, you will need to restart the X Window System. First, switch to runlevel 4:
/sbin/init 4
The graphical display will close, leaving only a terminal. When you reach the login: prompt, enter your username and password.
Then, as root in the terminal, switch to runlevel 5 to return to the graphical interface and start the X11 server:
/sbin/init 5
From the client machine, start a remote X11 session using X. For example:
X :1 -query
The command connects to the remote X11 server via XDMCP (replace with the hostname of the remote X11 server) and displays the remote graphical login screen on display :1 of the X11 server system (usually accessible by using the Ctrl-Alt-F8 key combination).
You can also access remote desktop sessions using a nested X11 server, which opens the remote desktop as a window in your current X11 session. Xnest allows users to open a remote desktop nested within their local X11 session. For example, run Xnest using the following command, replacing with the hostname of the remote X11 server:
Xnest :1 -query