GNOME Display Manager
# GNOME Display Manager

GNOME Display Manager (GDM) is a display manager (a graphical login manager) for the windowing systems X11 and Wayland.

The X Window System by default uses the XDM display manager. However, resolving XDM configuration issues typically involves editing a configuration file. GDM allows users to customize or troubleshoot settings without having to resort to a command line. Users can pick their session type on a per-login basis. GDM 2.38.0 is the last version that features customization with themes; subsequent releases do not support themes.

## Software architecture

GDM is a display manager that implements all significant features required for managing attached and remote displays. GDM was written from scratch and does not contain any XDM or X Consortium code.

### Components

GDM comprises the following components:

* Chooser – a program used to select a remote host as the source for a remote display on the attached display (gdm-host-chooser)
* Greeter – the graphical login window (provided by GNOME Shell)
* Pluggable authentication module (PAM)
* X Display Manager Control Protocol (XDMCP)

## Hidden features

Until version 2.22, GDM had a few Easter eggs, in the form of strings to be entered in the username box. These can be found in the source file "gui/guilogin.c", in a function named "evil".

* Dancing login – type "Start Dancing" to start, and "Stop Dancing" to stop.
   * (This requires the standard greeter ("GTK+ Greeter"), rather than the graphical one ("Themed Greeter")).
* "Gimme Random Cursor" – can be used repeatedly.
   * This changes the mouse cursor to a randomly selected 1 of 77 different "cursor fonts" as defined in the X11 specification.
* "Require Quarter" (or "Require Quater", for backward compatibility with a typo in the original), then log in normally – a dialog box that reads "Please insert 25 cents to log in." appears after entering the password. Clicking "OK" allows the login process to proceed as normal.

### Queen of England

Some of the copyright notices of GDM refer to the "Queen of England", whom release announcements from version 2.2.1 also named as a maintainer. Subsequently, developers realised that the title "Queen of England" has not existed since the Acts of Union of 1707.

