What's the difference between gnome, gnome-shell, and gnome-session-fallback?

I have the Ubuntu 12.04 Desktop freshly installed. If i execute the following command, what exactly happens?

sudo apt-get install gnome

And what is the difference between the above command and installing gnome-shell or gnome-session-fallback?

Solution 1:

If you check on the description of gnome

The GNOME Desktop Environment, with extra components

It will install both the Gnome Shell, and the Fallback session, along with the Gnome games, Evolution, Epiphany, Empathy, Rhythmbox, etc. It will install everything gnome.

Whereas gnome-shell will install just the Gnome Shell and its dependencies. Same is for the the fallback session package.

You can get this info either from Synaptic or using apt-cache show gnome and apt-cache show gnome-shell.

Solution 2:

I would like to expand on Uri Herrera above answer .

What is Gnome ?

It is basically a meta package consisting Both gnome-shell and gnome-fallback session.

GNOME Shell uses Mutter, a compositing window manager based on the Metacity window manager, and the Clutter toolkit to provide visual effects and hardware acceleration. According to GNOME Shell maintainer Owen Taylor, it is set up as a Mutter plugin largely written in Javascript.

From Gnome official page

Gnome-shell provides core interface functions like switching to windows and launching applications. GNOME Shell takes advantage of the capabilities of modern graphics hardware and introduces innovative user interface concepts to provide a delightful and easy to use experience.

You can refer the technology behind GNOME Shell page.

What is Fallback-mode?

If your computer's graphics card doesn't support certain features, a more basic version of the desktop will be displayed and you will see a message telling you what happened. This is called fallback mode, and it allows you to use GNOME on your computer without some of its more advanced features..

..Starting in fallback mode doesn't necessarily mean that your graphics card isn't good enough to run GNOME - it might just mean that you don't have the right drivers installed for your graphics card. If you can find better graphics card drivers for your computer, you may be able to run the full version of GNOME.

Basically it is for Unsupported Graphic Cards