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For what are repositories and how to install software from repositories in Ubuntu, please see the first part of this guide, Ubuntu Newbie Guide: apt-get and Synaptic To Install Applications.

Only the main, restricted and source code repositories are enabled by default in Ubuntu, so if you want to enable the other repositories in Ubuntu, go to System > Administration > Software Sources, on the first tab "Ubuntu Software" and check the repositories you want to enable (you can check them all: main, universe, restricted, multiverse and source code).


Here you can also set the server where you will be downloading the software from. The great part is that Ubuntu has servers all over the world, so you can add a server in your country, which makes downloads a lot faster.

A bit about what these repositories meaning:

# "Canonical-supported Open Source software (main)"
# "Proprietary drivers for devices (restricted)" [hardware-dependent]
# Community-maintained Open Source software - (universe)"
# "Proprietary drivers for devices (restricted)" - Commonly used software which is not available under a completely free license. This software is supported by the Ubuntu team.
# "Software restricted by copyright or legal issues (multiverse)" - Software that is "not free" and may require licensing. This software is not supported.

But there are a lot of other custom repositories which you can manually add. Why would you want to add custom repositories, you might ask. Well, because you may want to update the software faster that the Ubuntu team does (but remember that the applications might not be so stable if they weren't released in the Ubuntu repositories) or maybe add a repository for an application not included in the Ubuntu repositories.

Here is how to add a custom repository:

Go to System > Administration > Software Sources, on the second tab "Third-Party Software":


and add the repository, which usually comes in both compiled and source code versions (2 lines). Add each repository (which has this form: http://ppa.launchpad.net/psyke83/ubuntu intrepid main, where intrepid is the distribution name and main is repository channel which can be, as i said above universe, multiverse and so on).

These custom repositories also usually come with a key, which you can use to sign that repository by using your terminal and writing this (this command is usually found on the website from where you got the repository): wget --quiet http://packages.medibuntu.org/medibuntu-key.gpg -O - | sudo apt-key add - or you can import it by using the Import Key File button in Software Sources, under the Authentication tab.

The repositories can be found in this file: /etc/apt/sources.list.


These repositories download a list of software from which your computer knows about their existence. To update that list (so that your computer knows there is a new version of an application or that you added a new repository), open a terminal and write: sudo apt-get update

More about the great software update system in Ubuntu, in our next part of the Ubuntu Newbie Guide.