X display manager (program type)
The X Display Manager ( xdm ) is a part of the X Window System graphical user interfaces on Unix systems. The xdm is responsible to show the user a graphical login screen, can be entered via the user name and password. In addition, various specifications for the session to be started can be set here, such as the desktop environment or window manager to use. After successful registration, an X session will be started automatically. In terminal mode, the Xdm also used to select the workstation on which the session is to be started.
The xdm is also server process for X sessions over the network. To communicate the XDMCP protocol (X Display Manager Control Protocol) is used, which uses UDP port 177. However, XDMCP can also disable since it is only required when an X client attempts to connect from another PC.
Alternatives for xdm are the KDE Display Manager ( KDM) (see also KDE Plasma Workspaces ), the Gnome Display Manager (GDM ) (see also Gnome), the wdm (see also WindowMaker ), Entrance Display Manager ( see Enlightenment ) SLiM and LightDM.