Are you referring to the top right icon? That's what I was referring to in the initial bug report but apparently I wasn't clear enough. Anyway, when going to the top right icon, cand clicking it, a panel comes up with shutdown/restart/logout/switch user/lock screen, but no hibernate/sleep. (btw , I'm not even sure this belongs to gnome- session.) I'll be happy to provide any information. Thanks.
A related bug may be bug #55399 -- No hibernate option when logging out https://launchpad.net/bugs/54717 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
