This post should be a short post on how to change the default windows manager on the new but not yet official Ubuntu 11.10 Oneiric Ocelot. So far, Oneiric Alpha 3 has just been released a few weeks ago. Thus this released is not yet stable, but some hardcore users might be interested to be the early birds to try and have a peek on the new Ubuntu.
As far as we all already knew, Oneiric will be shipped with capabilities to run Gnome 3 along side with Unity which we might be missing on 11.04 Natty. So most of the anti-unity windows manager will be jumping and singing with joy once the developer team announced that the new version of Ubuntu will be able to run Gnome 3 which so far has been highly rated by most who have tried the gnome-shell.
So, to get my point here - once you've upgrade your Ubuntu to give a try to Oneiric Alpha 3, you might be wondering where the heck is Gnome 3 option on login screen? Be patient a bit guys, you need to install it by using apt-get. By default, the gnome-shell is now available in official repositories. So no more hardwork trying to find PPA for gnome-shell anymore. To install the latest version of gnome-shell for Ubuntu, you can simply type sudo apt-get install gnome-shell in your terminal. Once installed, just logout and choose the option for Gnome in the windows manager list during login session.
Once you have login, you might want to give it a few test drives. Only when you completely satisfied with the new Gnome 3 than you can consider to change the default windows manager from Unity(which is default for Ubuntu) into Gnome 3(which we need to edit certain config files). So, since the version is still in alpha - you should not expect that everything will work according to what it should. To change the default windows manager, usually we can do it by selecting Login Screen on the menu. But in the new alpha, this option is not yet available. So to change the default WM, all you need to do is open your terminal, and edit lightdm.conf which is located in /etc/lightdm/ folder.
sudo nano /etc/lightdm/lightdm.conf
Just change the user-session to gnome and autologin-user to gnome. Then you should reboot your machine and see if by default, the windows manager is now in gnome-shell and not unity. Drop comment for any problems or if you got a better way to accomplished this, just share it in comment sections. Thanks!