Configuring XDM

Configuring XDM to accept remote logins begins with the /etc/X11/xdm/xdm-config file. The key change is in the following line, which usually appears near the end of the

DisplayManager.requestPort: 0

This line tells XDMCP not to listen on its usual port. Such a configuration is common on workstations, which normally manage their local X servers more directly. Change the 0 in this line to 177 or comment out the line by placing a hash mark (#) or exclamation mark (!) at the start of the line.

In addition to xdm-config, you must edit the /etc/X11/xdm/Xaccess file, which controls what XDMCP clients may access the XDMCP server. This file is likely to contain lines such as the following, but they'll probably be commented out:


These lines tell the system to accept logins from any host and to provide a chooser (a list of available XDMCP servers on the local network) to any client that asks for one. The default commented-out configuration denies access to all computers, so uncommenting the lines enables access. Instead of using an asterisk (*), though, you may want to specify computers by name. An asterisk can stand in for part of a name. For instance, * grants access to any computer in the domain.

The /etc/X11/xdm/Xservers file lists the displays that XDM should manage. A typical configuration includes a line like the following:

:0 local /bin/nice -n -10 /usr/X11R6/bin/X -deferglyphs 16

Note This line varies greatly from one system to another. The :0 local part is the least likely to vary, and the line will also include a call to your X server program. Other details may differ.

This line tells XDM to run /usr/X11 R6/bin/X and to display an XDMCP login prompt on this server whenever the XDMCP server itself runs. If you don't want to start X locally but you do want to accept remote XDMCP logins, comment this line out. When you restart runlevel 5, the system should not start X, but it should accept remote XDMCP logins.

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