X Display Manager

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This is about the X Window Display Manager. XDM also refers to the XML data model used in XPath 2.0, XSLT 2.0, and XQuery.

XDM

A screenshot of an XDM login screen
Original author(s)	Keith Packard
Developer(s)	X.Org Foundation
Initial release	October 1988
Stable release	1.1.9 / 2009-09-18; 2 months ago [1]
Type	X display manager
License	MIT License

XDM (in full, the X Window Display Manager) is the default display manager for the X Window System. It is a bare-bones X display manager. It was introduced with X11 Release 3 in October 1988, to support the standalone X terminals that were just coming onto the market. It was written by Keith Packard.

Because of its lack of user-friendliness, users of GNOME, KDE, Enlightenment or Window Maker tend to use GDM, KDM, Entrance or wdm instead of XDM.

Customization

XDM has two main files used to define how XDM is displayed, they are Xresources and Xsetup (sometimes Xsetup_0). Xsetup_0 is used to tell XDM how to start-up, and Xresources configures the login window (command Xlogin*[function]), chooser (command Chooser*[function]) and XConsole (command XConsole*[function]).

Xsetup

Xsetup is the file that defines how XDM will open. You can set the background (sometimes called the 'Desktop' or 'root window'.

To tell XDM that you are setting the background you would enter the line:

/usr/X11R6/bin/xsetroot

this sends XDM off to look at the content of the file 'xsetroot' in /usr/X11R6/bin, xsetroot is the background.

To set a background colour, enter:

-solid\

on the same line. This tells XDM to set a solid colour, and the optional '\' says that the colour will be on the next line.

for a background pattern/image, insert:

-bitmap\

on the same line, and on the next enter the path of a bitmap image (bitmap images are images with the following file format: .png, .bmp, .jpg, .jpeg, .gif - a bitmap is an image made with a map, of bits, ie. pixels (without layers)). A path might look like /home/USERNAME/my-images/my-favorite-background.png.

Xresources

The Xresources file can be used to configure the appearance of X Window programs and other objects such as the login window.

Size and position can set these with the functions .width, .height, .x and .y, where x and y represent position. These may all be set together using an argument of the form: -geometry HEIGHTxWIDTH+X+Y.

For example, to open the ubiquitous xclock application with a gray and black colour scheme, at the top right hand corner of the screen, and with a height and width of 100 pixels, the following line could be added to Xresources;

xclock -hl black -hd black -bg steelgray -fg gray -geometry 100x100+0+0 &

References

• Linda Mui and Eric Pearce, X Window System Volume 8: X Window System Administrator's Guide for X11 Release 4 and Release 5, 3rd edition (O'Reilly and Associates, July 1993; softcover ISBN 0-937175-83-8)
• XDM(1) manual page (XFree86.org)

External links

• xdm manual page
• Taming The X Display Manager
• Configuring XDM — a graphical login interface for Linux or UNIX (Mark Nielsen, Linux Gazette #43, July 1999)
• - configuring XDM with shutdown/reboot buttons and background image

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