Translations by Adi Roiban

deb http://ppa.launchpad.net/<emphasis>user</emphasis>/ppa/<emphasis>ppa-name</emphasis> lucid main

Some packages from the <emphasis>main</emphasis> and <emphasis>restricted</emphasis> Ubuntu package repositories can be installed from the Ubuntu installation CD. Simply insert your Ubuntu installation CD and open <menuchoice><guimenu>System</guimenu><guimenuitem>Administration</guimenuitem><guimenuitem>Synaptic Package Manager</guimenuitem></menuchoice>. To list only packages on the Ubuntu installation CD, click on the <guibutton>Origin</guibutton> button in the lower left corner of the Synaptic window. The packages should be listed under the <guimenuitem>Ubuntu 10.04_Lucid_Lynx</guimenuitem> section.

deb http://archive.ubuntu.com/ubuntu/ lucid main

Adding, Removing and Updating Applications

How is software installation on Ubuntu different from on Windows?

Ubuntu handles software installation in a very different way to Windows.

If you want to install an application on Windows, you must normally buy a CD containing the software, or download an installer package from the Internet. You then run the installer program, which guides you through the installation process.

On Ubuntu, you simply open a <emphasis>package manager</emphasis>, search for the application that you want and click a button to install it. Removing an application is just as simple.

The package manager downloads applications from a <emphasis>software repository</emphasis>, which is a location on the Internet which stores a collection of applications. These applications come bundled in <emphasis>packages</emphasis>, which contain all of the information needed for installation. You can download packages yourself, using your web browser, if you like, but it is generally much more convenient to let the package manager handle this for you.

Some packages depend on other packages being installed in order to work. For example, a word processing package may require a printing package to be installed. The package manager automatically installs these <emphasis>dependencies</emphasis> for you.

By default, only applications from the official Ubuntu software repositories are available in your package manager. If you cannot find the application that you want in the default repositories, you can add other (<quote>third-party</quote>) repositories and install it from there.

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>.

Other methods of installing applications

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

If you are asked if you would like to mark additional changes, click <guibutton>Mark</guibutton>.

Select any other applications that you would like to install.

Click <guibutton>Apply</guibutton>, and then click <guibutton>Apply</guibutton> in the window that appears. The applications that you chose will be downloaded and installed.

You can download and install applications from websites. These applications are contained in Debian (.deb) packages. To install a Debian package:

Download the package from a website.

Double-click the package. It will be opened in the Package Installer.

Click <guibutton>Install</guibutton> to install the package.

Installing single packages in this way is not recommended, for the following reasons:

The packages have not been checked for security by Ubuntu members, and could contain software which harms your computer. You should only download single packages from websites that you trust.

The package may require some extra software to run, which cannot be installed automatically. You will have to find and install this software yourself.

Clicking a link on a web page

Some web pages have links which install applications when you click them. These are known as <quote>apt:</quote> links. After clicking the link, you will be asked if you would like to install additional software. Click <guibutton>Install</guibutton> to start the installation process.

The application can only be downloaded and installed if it is available in a software repository which is currently enabled on your computer. This means that websites cannot trick you into installing software which is potentially harmful to your computer.

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

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.

Software is available from third-party sources, as well as from the default Ubuntu software repositories. If you want to install software from a third-party software repository, you must add it to the package manager's list of available repositories.

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>.

Packages from the new repository should now be available in your package manager.

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>.

Enabling other CDs that can be used to install packages

Click <menuchoice><guimenu>System</guimenu><guimenuitem>Administration</guimenuitem><guimenuitem>Software Sources</guimenuitem></menuchoice>.

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

Using APTonCD to install packages

<application>APTonCD</application> can be used to create a CD that contains all the packages you have on your system, or it can create CDs with packages or entire repositories of your choice. In a package manager such as <application>Synaptic</application>, find the <emphasis>aptoncd</emphasis> package and install it.

What is restricted and non-free software?