How to Install Gnome 3 on Ubuntu 12.10
If you're using Ubuntu 12.10 with Unity or some other desktop environment and want to switch to a complete GNOME 3 desktop experience without installing Ubuntu GNOME Remix 12.10, you can do this by simply installing a few packages.
Using the instructions below, you won't just install GNOME Shell, but also the default settings and applications that come with Ubuntu GNOME Remix. There are also some optional steps to install the GNOME 3 applications which are missing from Ubuntu GNOME Remix.
No, the command in the header won't work, but you'll get a complete GNOME 3 experience in Ubuntu 12.10 by following the steps below.
1. Install the Ubuntu GNOME packages
To install the default Ubuntu GNOME Remix packages and get the default settings as well, use the command below. It will install GNOME Shell along with the GNOME3 core applications.
[sourcecode language="bash"]sudo apt-get install ubuntu-gnome-desktop ubuntu-gnome-default-settings[/sourcecode]
When prompted, select GDM as the default display manager.
If you already had GDM installed and the package manager didn't prompt you to choose between LightDM and GDM or you've selected LightDM by mistake, you can run the following command:
[sourcecode language="bash"]sudo dpkg-reconfigure gdm[/sourcecode]
And select GDM instead of LightDM (more about changing the display manager, here). You can use LightDM with GNOME Shell, but you won't get the complete GNOME 3 experience - for instance, GNOME Shell won't use the new GNOME 3.6 lock screen.
It is also a good idea to remove the "ubuntu-settings" package:
[sourcecode language="bash"]sudo apt-get remove ubuntu-settings[/sourcecode]
Note that removing this package, the "ubuntu-desktop" package will be removed as well. This is just a meta package and your system shouldn't be affected by it.
The "ubuntu-settings" package is used to set various Ubuntu defaults, like the window button order, which Rhythmbox plugins are enabled by default and so on.