X display manager
The X Display Manager ( Xdm ) is a display manager program for the X Window System . These programs create graphical user interfaces on Unix systems.
The display manager shows a graphical login screen for entering the user name and password . In addition, specifications for the session to be restarted can be set here, for example the desktop environment to be used or the window manager .
After successful registration is for this user an X - session started (by taking over the existing already for the welcome screen (Greeter) Session).
When accessing via the network , the display manager is also used to select the workstation on which the session is to be started. The XDMCP protocol (X Display Manager Control Protocol), which uses the UDP port 177, is used for communication . However, XDMCP can also be deactivated as it is only required if a remote user wants to connect.
Alternatives to Xdm as historically the first display manager are the Light Display Manager (LightDM), the Gnome Display Manager (GDM), the KDE Display Manager (KDM) and the Simple Login Manager (SLiM) as well as wdm (see also Window Maker ) and Entrance Display Manager (see also Enlightenment ).
