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Install GNOME-Shell on Ubuntu 9.10 Karmic Koala
This article outlines the steps required to install and run the latest previews of GNOME Shell, which will become GNOME 3.0. The final release isn't scheduled until later this year, but there are preview snapshots available for testing and feedback. Installation of GNOME Shell can be done alongside your normal installation, so you don't need to worry about it interfering with your regular desktop.