The content of /usr/share/xsessions/ubuntu.desktop states that:
[Desktop Entry] Name=Ubuntu Comment=This session logs you into Ubuntu Exec=env GNOME_SHELL_SESSION_MODE=ubuntu gnome-session --session=ubuntu TryExec=gnome-shell Type=Application DesktopNames=ubuntu:GNOME X-Ubuntu-Gettext-Domain=gnome-session-3.0 From Exec, I see that the Linux shell environmental variable GNOME_SHELL_SESSION_MODE is given the value ubuntu and the binary /usr/bin/gnome-session is told to run a ubuntu session.
Questions: What is a ubuntu session? Why isn't it a systemd --user session as is mentioned in GDM's documentation?
1 Answer
According to Ubuntu's documentation, gnome-session is a program to start a GNOME desktop environment. Also, the option --session=SESSION means to use the applications defined in SESSION.session. And, if not specified, gnome.session will be used.
Accordingly, --session=ubuntu should refer to the file /usr/share/gnome-session/sessions/ubuntu.session which writes:
[GNOME Session] Name=Ubuntu RequiredComponents=org.gnome.Shell;org.gnome.SettingsDaemon.A11ySettings;org.gnome.SettingsDaemon.Clipboard;org.gnome.SettingsDaemon.Color;org.gnome.SettingsDaemon.Datetime;org.gnome.SettingsDaemon.Housekeeping;org.gnome.SettingsDaemon.Keyboard;org.gnome.SettingsDaemon.MediaKeys;org.gnome.SettingsDaemon.Mouse;org.gnome.SettingsDaemon.Power;org.gnome.SettingsDaemon.PrintNotifications;org.gnome.SettingsDaemon.Rfkill;org.gnome.SettingsDaemon.ScreensaverProxy;org.gnome.SettingsDaemon.Sharing;org.gnome.SettingsDaemon.Smartcard;org.gnome.SettingsDaemon.Sound;org.gnome.SettingsDaemon.Wacom;org.gnome.SettingsDaemon.XSettings; According to @user535733 comment, while 18.04 was being put together, there were issues and systemd --user level integration was not done for 18.04.
