how to replace Unity with Gnome2 in the Ubuntu 12.04

many gnome2 user don’t like the unity of ubuntu 12.04, so if you want to replace it with the Gnome2, you can simply install

sudo apt-get install gnome-session-fallback

and then logout and relogin, select classic mode.

Since only indicator-applet-complete was preinstalled in the ubuntu 12.04, so none indicator can be removed by alt/alt+win + right mouse click, so you also need to install

sudo apt-get install indicator-applet indicator-applet-session

now you can config or place your indicator-applet as usual.