Translations by Connor Imes

Click <menuchoice><guimenu>Applications</guimenu><guimenuitem>Ubuntu Software Center</guimenuitem></menuchoice>.

For more information about using the <application>Ubuntu Software Center</application>, consult the <ulink type="help" url="ghelp:software-center">Ubuntu Software Center Manual</ulink>.

Synaptic can be used to manage advanced software packages (such as server applications) which Software Center does not manage.

In the <emphasis>Installed Software</emphasis> section, find the application that you want to remove by finding it in the list or by searching for it.

If the application that you want to remove is not available in the <application>Ubuntu Software Center</application>, use Synaptic (<menuchoice><guimenu>System</guimenu><guimenuitem>Administration</guimenuitem><guimenuitem>Synaptic Package Manager</guimenuitem></menuchoice>) to remove it instead.

Only add software repositories from sources that you trust. Third-party software repositories are not checked for security by Ubuntu members, and may contain software which is harmful to your computer.

Open <menuchoice><guimenu>System</guimenu><guimenuitem>Administration</guimenuitem><guimenuitem>Software Sources</guimenuitem></menuchoice> and select <guilabel>Other Software</guilabel>.

You can also add the GPG key using the terminal by entering the following command:

sudo apt-key adv --recv-keys --keyserver keyserver.ubuntu.com key-fingerprint

Adding a Personal Package Archive (PPA)

<ulink url="https://launchpad.net/">Launchpad</ulink> provides all users with their own Personal Package Archive (PPA) that can be used to build and store Ubuntu packages. In the same way that you can add a normal software repository, you can also add a PPA to the package manager's list of available repositories. PPAs work like normal Ubuntu archives. You can install software in the usual way -- for example, through apt-get or synaptic -- and whenever there's an update Ubuntu will prompt you to install it.

You download and install PPA packages at your own risk. Ubuntu, Launchpad and Canonical do not endorse these packages. You must be certain that you trust the PPA owner before you install their software.

You should begin by familiarizing yourself with <xref linkend="adding-repos"/> before beginning.

The APT line for the PPA can be found on the PPA overview page on Launchpad, and should look similar to the following:

As a security measure, all PPAs use a unique GPG key to digitally sign the packages that they provide. This makes it easy to check that the packages have not been tampered with since Launchpad built them and to be sure that you are downloading from the PPA that you want. In order for your package manager to be able to check this, you need the public key that corresponds to the signatures. The key should be available for download on the PPA overview page on Launchpad. Until you add the PPA's key to your system, you will see warnings that you are downloading from an untrusted source.

The key used to sign a PPA is listed on the PPA overview page. Instructions on how to add the key can be found in <xref linkend="adding-repos"/>.

Additional information about adding a PPA repository can be found on <ulink url="https://help.launchpad.net/Packaging/PPA">Launchpad</ulink>.

Select <guilabel>Other Software</guilabel> and click on the <guibutton>Add CD-ROM</guibutton> button.

What is restricted and non-free software?

In some cases, restricted software is the only option. Such cases include software for the playback of certain audio and video formats, some fonts and <ulink type="help" url="ghelp:hardware#jockey">drivers for some graphics cards</ulink>.

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