gnome-session

gnome-session
Prev	Part I. Commands	Next

Description

The gnome-session program starts up the GNOME desktop environment. This command is typically executed by your login manager (either GDM, SDDM, lightdm, or other). It will load either your saved session, or it will provide a default session for the user as defined by the system administrator (or the default GNOME installation on your system).

The default session is defined in gnome.session, a .desktop-like file that is looked for in $XDG_CONFIG_HOME/gnome-session/sessions, $XDG_CONFIG_DIRS/gnome-session/sessions and $XDG_DATA_DIRS/gnome-session/sessions.

Options

--session=SESSION: Use the applications defined in SESSION.session. If not specified, gnome.session will be used.
--debug: Enable debugging code.

systemd

gnome-session uses systemd for the bulk of its service management. systemd provides the two special targets for desktop integration: graphical-session.target and graphical-session-pre.target. These work across desktop environments, and should be used if possible. gnome-session provides the following additional GNOME-specific targets:

gnome-session.target: Generic unit that will be active throughout the session. Similar to graphical-session.target.
gnome-session-pre.target: Used for tasks that need to be done before session startup. Similar to graphical-session-pre.target.
gnome-session-x11@SESSION.target, gnome-session-wayland@SESSION.target: Main unit started for X11/wayland based session. SESSION is set according to the session that is passed in via --session.
gnome-session-x11.target, gnome-session-wayland.target: Convenience units without the session embedded into the target.
gnome-session@SESSION.target: Convenience unit with just the SESSION information embedded.
gnome-session-basic-services.target: Special unit that lists basic services that are needed by any GNOME session built around gnome-shell. This allows for convenient reuse by kiosk sessions like the GDM login screen.
gnome-session-x11-services.target: Special unit started when X11 services are needed. Programs will need to use the special GNOME_SETUP_DISPLAY environment variable instead of DISPLAY.

Note that care must be taken to set appropriate After= rules. It is also strongly recommended to always do this in combination with BindsTo= or PartOf= on one of the core targets (e.g. graphical-session.target).

Units are required to set CollectMode=inactive-or-failed. In addition, it is strongly recommended to set TimeoutStopSec=5 so that logout will not be delayed indefinitely in case the process does not stop properly.

Session definition

Sessions are defined in .session files, that are using a .desktop-like format, with the following keys in the GNOME Session group:

Name: Name of the session. This can be localized.
Kiosk: Kiosk sessions are special single-purpose sessions that are built around starting some specific app. For instance, a kiosk session may run a full-screen web browser that's locked to a specific page. In GNOME, we use kiosk sessions for the login screen (where the app is the login screen UI) and the initial-setup first boot experience. When set to true, gnome-session will make no attempt to autostart any .desktop files, and will instead require that the session configures all required functionality via systemd.

Here is an example of a session definition:

[GNOME Session]
Name=GNOME

The .session files are loaded from $XDG_CONFIG_HOME/gnome-session/sessions, $XDG_CONFIG_DIRS/gnome-session/sessions and $XDG_DATA_DIRS/gnome-session/sessions.

Session definitions don't do anything on their own, and they need to be accompanied by systemd configuration to provide some functionality (i.e. launch services). The recommended way to do that is by hooking into one of the targets described above. For instance: when defining a session named foobar, you can create a systemd drop-in file in /etc/systemd/user/gnome-session@foobar.target.d/session.conf and define Requires= and Wants= dependencies to tell systemd what services it needs to start when launching this session.

Files

      $XDG_CONFIG_HOME/autostart
      $XDG_CONFIG_DIRS/autostart
      /usr/share/gnome/autostart

Applications defined via .desktop files in those directories will be started on login. Note that previous versions of gnome-session would launch services from here, but this is no longer the case. Services should now be configured via systemd unit files

      $XDG_CONFIG_HOME/gnome-session/sessions
      $XDG_CONFIG_DIRS/gnome-session/sessions
      $XDG_DATA_DIRS/gnome-session/sessions

These directories contain the .session files that can be used with the --session option.

Bugs

If you find bugs in the gnome-session program, please report these on https://gitlab.gnome.org/GNOME/gnome-session/issues.

Name

Synopsis