Starting from Gnome 3.x the old user interface of this desktop environment evolved in a new UI called Gnome Shell. On Ubuntu this shell is not available by default, since Unity is the main shell presented after a new installation. Luckly the Gnome Team is maintaining an updated PPA that aims to integrate Gnome in Ubuntu.
To install Gnome Shell on Ubuntu (only Ubuntu >= 11.04 is supported) just execute these commands:
sudo add-apt-repository ppa:gnome3-team/gnome3 sudo apt-get update sudo apt-get install gnome-shell
This will install the Gnome Shell 3.2 on your Ubuntu distribution.
Installing Gnome Shell Extensions
The Gnome Shell comes with no extensions installed, the updated one are packaged in a different PPA. To install them execute the following commands:
sudo add-apt-repository ppa:ferramroberto/gnome3 sudo apt-get update sudo apt-get install gnome-shell-extensions-common sudo apt-get install gnome-tweak-tool
Note (please read)
Some people are asking me: why a PPA? Gnome 3 is in Oneiric already! It's not exact. First of all the version shipped with Oneiric is not updated, then some packages are missing and even extensions are packaged separately.