How do I enable the "extras" repository?

This repository should be enabled by default and is only available for 10.10 and up.

Ubuntu Desktop

In the Software Center (Applications -> Ubuntu Software Center) navigate to Edit -> Software Sources...

From there navigate to the Other Software tab and ensure the Independent sources are selected

Press close and allow the sources to reload.

Ubuntu Server

Open the APT Sources list

sudoedit /etc/apt/sources.list

Locate the lines which say

Remove the hash (#) tag from those lines. If the hashes are not present then that source is already enabled. If those lines aren't there at all you will need to add them to the bottom of the file:

deb http://extras.ubuntu.com/ubuntu precise main
deb-src http://extras.ubuntu.com/ubuntu precise main

Close the editor and run

sudo apt-get update

This will download the package cache from the extra's location.

Reference:

• https://wiki.ubuntu.com/AppReviews