GDM for Debian
==============

Configuration overview
----------------------

The configuration for the GDM daemon is completely different from the 
older versions (in former package gdm).

For the daemon itself:
 * The autologin options can be chosen from the “User” tab of the GNOME control
   center.
 * Other options (like XDMCP) can be set in /etc/gdm3/custom.conf. The 
   list of available options can be found in /usr/share/gdm/gdm.schemas.

The greeter - which is the interface that welcomes you on the 
computer - uses a minimal GNOME session to startup. Its settings are set 
through GSettings, but using a specific configuration.
 * You can force the GSettings settings in /etc/gdm3/greeter.dconf-defaults.
 * After changing any of the settings, you need to run “systemctl reload gdm”
   to take them into account.

Custom X11 sessions
-------------------

Since Debian 12, GDM does not provide a session type that reads ~/.xsession
or the X11 session managers managed by update-alternatives. If this
session type is required:

- create a directory /etc/X11/sessions/
- copy /usr/share/doc/gdm3/examples/custom-x11-session.desktop
  to /etc/X11/sessions/
- edit as required

See the GNOME user documentation in the gnome-user-docs package for
more details of how to configure custom X11 sessions.

X11 authentication
------------------

Upon session startup, GDM sets the XAUTHORITY environment variable to a 
session-specific file in /run/gdm3.

Applications and scripts that assume this file is set to ~/.Xauthority 
will not work. To access the display you need both DISPLAY and 
XAUTHORITY variables.

"I get ugly fonts"
------------------

In the past, as a quick workaround, GDM imposed a 96 DPI settings by
passing "-dpi 96" to the X server on startup.  This is a bad idea as
there's no reason to override standard DPI detection mechanisms for all
screens which might or might not be 96 DPI screens.

DPI should be computed automatically based on the information on your
screen that Xorg gets; ideally, Xorg would get the DPI right, but you
can help Xorg by configuring it with your exact screen properties.


Face Browser
------------

If you enable the face browser in the greeter, GDM will look for face 
files (any image format supported by GTK+). You can configure the face 
for your user in the “User” tab of the GNOME control center.
