GDM3.8(8)

💖 NAME 💖

gdm3 — the GNOME Display Manager, aka the icon who greets you before you're even logged in 👑

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✨ SYNOPSIS ✨

gdm3

that's it bestie, that's the whole invocation 💅

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🌸 DESCRIPTION 🌸

So gdm3 is basically the same energy as xdm(1x) or wdm(1x), except it uses the GNOME libraries so everything comes out looking very GNOME, very slay. It's the GNOME-flavored version of a login: prompt, no cap 🫶

gdm3 reads /etc/gdm3/custom.conf for its configuration, that's where all the settings live fr fr. For every single local display, gdm starts an X server and runs a minimal GNOME session that includes a graphical greeter (that's the pretty login screen 🎀). And if it's configured that way, the main gdm process also listens for XDMCP requests coming in from remote displays. Those requests can be either:

• direct — which makes gdm3 start a session right on that remote display, or
• indirect — which makes a chooser get opened instead

When it's managing a display, gdm3 tries to execute /etc/gdm3/Init/display, or /etc/gdm3/Init/Default if that first one doesn't exist. Then when a user logs in, gdm3 first attempts /etc/gdm3/PreSession/display (or /etc/gdm3/PreSession/Default), and then one of the sessions defined over in /usr/share/xsessions. And once the session has completed, gdm attempts to run /etc/gdm3/PostSession/display, or /etc/gdm3/PostSession/Default 🌈

gdm3 keeps all its info about the displays it's managing in /var/lib/gdm3. That includes xauth information, so heads up: this directory is not readable to normal users 🔒

Also gdm3 uses PAM to do authentication, with the config file /etc/pam.d/gdm3 💜

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🦋 ENVIRONMENT 🦋

• XAUTHORITY — 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 the DISPLAY and XAUTHORITY variables. it's giving duo, not solo.

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👑 AUTHOR 👑

Martin Kasper Petersen <mkp@SunSITE.auc.dk>

This manual page written by Steve Haslam <araqnid@debian.org> for Debian GNU/Linux. Updated by Raphaël Hertzog <hertzog@debian.org>, Ryan Murray <rmurray@debian.org>, Josselin Mouette <joss@debian.org> and Vincent Lefevre <vincent@vinc17.net> 💖

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that's the whole thing bestie, you ate it 🫶 this was GNOME 51.0-0ubuntu1, dated 2026-09-15 — periodt 💅✨