Compiz Fusion is turn on under Ubuntu by default if your hardware support. But there’s another way to enjoy the Compositing feature, fast and simple.
First, make sure that Compiz Fusion is turn off.
Open System > Preferences > Appearance > Visual Effects, and select None.
Then press Alt + F2 or open the Terminal and type: gconf-editor to open the Configuration Editor.
Find the key: /apps/metacity/general/compositing_manager and enable it.
Here how to do the same thing via command line:
gconftool-2 -s '/apps/metacity/general/compositing_manager' --type bool true