Configure a user default session
The default session is retrieved from a program called AccountsService. AccountsService stores this information in the /var/lib/AccountsService/users/ directory.
In GNOME 2, the .dmrc file in the user home directory was used to create default sessions. This .dmrc file is no longer used.
Specify a default session for a user
Make sure that you have the gnome-session-xsession package installed on your system.
Navigate to the /usr/share/xsessions directory where you can find .desktop files for each of the available sessions. Consult the contents of the .desktop files to determine the session you want to use.
To specify a default session for a user, update the user’s account service in the /var/lib/AccountsService/users/username file:
[User] Language= XSession=gnome-classic
In this sample, /usr/share/xsessions/gnome-classic.desktop file.has been set as the default session, using the
After specifying a default session for the user, that session will be used the next time the user logs in, unless the user selects a different session from the login screen.