If you enable auto log-in in Ubuntu 11.10 Oneiric, it automatically logs into Unity. Some people installed gnome-shell Gnome 3 desktop and want Ubuntu auto log into gnome-shell. Normally, we first disable auto log-in behavior, log out and back into gnome-shell, and finally in Gnome 3 desktop enable auto log-in again.

Unfortunately, this settings doesn’t work for me, but I found a command-line solution