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Adding, Removing and Updating Applications

In this section you can learn how to use a package manager to add or remove software in Xubuntu with a few clicks. You can also learn about more advanced techniques of managing applications and discover some optional applications to add to Xubuntu.

What is a package manager?

A package manager is a program that helps the user to efficiently and safely install, update, or uninstall software on a computer. Package managers also keep track of all the components that software needs to work correctly.

There are three main package managers you can use in Xubuntu:

<link linkend="gnome-app-install"><application>Add/Remove Programs</application></link> - The easiest way to install and uninstall programs.

<link linkend="synaptic"><application>Synaptic</application></link> - Advanced control of software and other system components.

<link linkend="apt"><application>Apt</application></link> - If you prefer using the Terminal.

If you open more than one of these programs at once, they may not work. Close them all, and open just one.

You need administrative access to use any of these programs. See <link linkend="root-and-sudo">Administrative Tasks</link> for more details.

Software repositories

A software repository is a place from which you can download and install software over the Internet.

There are thousands of programs available to install on Xubuntu. These programs are stored in software archives called (<emphasis>repositories</emphasis>) and are made freely available for installation over the Internet. This makes it very easy to install new programs on your system, and it is also very secure, because each program you install is built specially for Xubuntu and checked before it is installed.

To organize the software, Xubuntu repositories are categorized into four groups: <emphasis>Main</emphasis>, <emphasis>Restricted</emphasis>, <emphasis>Universe</emphasis>, and <emphasis>Multiverse</emphasis>. The rationale used to determine which software goes into which category is based on the level of support that software development teams provide for a program and the level of compliance the program has to the <ulink url="http://www.ubuntu.com/ubuntu/philosophy">Free Software Philosophy</ulink>.

The standard Xubuntu Install CD contains some software from the <emphasis>Main</emphasis> and <emphasis>Restricted</emphasis> categories.

If your system is connected to the Internet, many more software programs are made available for installation. For example, the <quote>Universe</quote> and <quote>Multiverse</quote> repositories are only available over the Internet.

The <emphasis>Multiverse</emphasis> repository contains software which has been classified as <emphasis>non-free</emphasis>. This software may not be permitted in some jurisdictions. When installing each package from this repository, you should verify that the laws of your country permit you to use it. Also, this software may not include security updates.

You can find more information about the Repositories available <ulink url="http://www.ubuntu.com/ubuntu/components">on the Ubuntu website</ulink>.

Adding extra repositories

It is possible to add extra repositories, such as those provided by third parties or those for older versions of Xubuntu.

Be careful when installing software from third-party repositories. Software from third-party repositories is not supported by Xubuntu. The software they contain may not have been tested with Xubuntu, and could cause your system to break.

Open <menuchoice><guimenu>Applications</guimenu><guisubmenu>System</guisubmenu><guimenuitem>Software Sources</guimenuitem></menuchoice> and press <guilabel>Third-Party Software</guilabel>.

Press <guibutton>Add</guibutton> to add a new repository.

Enter the <emphasis>APT line</emphasis> for the extra repository. This should be available from the website of the repository or similar, and should look similar to the following:

deb http://ftp.debian.org etch main

Press <guibutton>Add Source</guibutton> and then click <guibutton>Close</guibutton> to save your changes.

Most software repositories use a GPG key to digitally sign the files they provide, which makes it easy to check that the files haven't been tampered with since their creation. In order for apt 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 repository's website.

Once you have downloaded the GPG key, import the key by selecting the Authenticate tab, and clicking on <emphasis>Import Key File...</emphasis>, and then selecting the GPG key to be imported.

Click <guibutton>Reload</guibutton> in the package manager to update the list of available packages.

Add/Remove Applications

With the <guimenuitem>Add/Remove…</guimenuitem> item in the <guimenu>Applications</guimenu> menu, you can install programs to do new things with Xubuntu. You can also remove programs you don't want. You need administrative access to use <application>Add/Remove Programs</application> (see <link linkend="root-and-sudo">Administrative Tasks</link> for more details).

If you know the name of a program you want to install, enter it in the <guilabel>Search</guilabel> field. Otherwise, begin by choosing a software category on the left.

Programs that are already installed begin with a check mark next to their name. Uncheck a program if you want to remove it from your computer.

When you click <guibutton>Apply</guibutton> or <guibutton>OK</guibutton>, any new software will be downloaded from the Internet, and Xubuntu will make the changes you selected. If you have not activated the online package archive, you may be asked to insert your Xubuntu CD-ROM to install some packages.