Closed all the terminals. Clicked on the footprint.
Chose Log out.
Really log out? Chose Yes.
Username and password entered.
Screen goes black for an instant, then Gnome reappears with another session, wanting to know my username and password.
These entered, Gnome is back on the screen.
Gnome Help is no use because there is a 'Could not load default TOC page' message on the Gnome browser.
I'm really pleased that it is so loyal and friendly, but I really would like it to go to sleep sometime.
Apart from an uncontrolled crash landing, someone remind me please, how do I get out of it?