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GDM3.8(8) Debian GNU/Linux GDM3.8(8)


gdm3 - GNOME Display Manager




gdm3 is the equivalent of xdm(1x) or wdm(1x), but uses the GNOME libraries to provide a GNOME look-and-feel. It provides the GNOME equivalent of a "login:" prompt.

gdm3 reads /etc/gdm3/daemon.conf for its configuration. For each local display, gdm starts an X server and runs a minimal GNOME session including a graphical greeter. If configured so, the main gdm process also listens for XDMCP requests from remote displays. These requests can either be direct, causing gdm3 to start a session on the remote display, or indirect, causing a chooser to be opened.

When managing a display, gdm3 attempts to execute /etc/gdm3/Init/display, or /etc/gdm3/Init/Default if that does not exist. When a user logs in, gdm3 first attempts /etc/gdm3/PreSession/display (or /etc/gdm3/PreSession/Default), and then one of the sessions defined in /usr/share/xsessions. When the session has completed, gdm attempts to run /etc/gdm3/PostSession/display, or /etc/gdm3/PostSession/Default.

gdm3 maintains information about the displays it is managing in /var/lib/gdm3. This includes xauth information, so this directory is not readable to normal users.

gdm3 uses PAM to perform authentication using the config file /etc/pam.d/gdm3.


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.


Martin Kasper Petersen <>

This manual page written by Steve Haslam <> for Debian GNU/Linux. Updated by Raphaeel Hertzog <>, Ryan Murray <>, Josselin Mouette <> and Vincent Lefevre <>.

2023-01-29 GNOME 43.0-3