A hidden file in your ["home directory"].

A .xinitrc sample is:

xsetbg -fullscreen /morphix/background.png & exec ["gnome-session"]

That uses the command to start GNOME : gnome-session.

You can also use instead:

and so on.

Change

If you want to choose i.e. between gnome and xfce when you want to change from one to the other, then you can do (as normal user) :

["nano"] .xinitrc

and make it look like this (and then exit nano saving changes: Ctrl-x, y, Enter):

This will tell "["startx"]" to start gnome. When you want to start xfce, do "nano .xinitrc" again and make it look like this: