Если кому интересно, нужно править вот этот файл
/usr/share/gnome/default.sessionА в документации говорят что и консольным приложением можно
Setting Session Defaults
The following table lists the files that contain default session information:
File
Description
/usr/share/gnome/default.session
Default session file. Default session details are stored in this file.
$HOME/.gnome2/session
User session file. When a user modifies the session, the details are stored in this file.
To set default session details for all users, modify the default session file.
To restore the default session settings for a user, delete the session file from the home directory of the user. If no user session file is present, the default settings in /usr/share/gnome/default.session are used.
To save the current session as the default session, users can run the gnome-session-save command.