Translations by Cynthia Cheung

ubuntu-doc@lists.ubuntu.com (Ubuntu Documentation Project)

Adding and Removing Software

Adding, Removing and Updating Applications

This document is maintained by the Ubuntu documentation team (https://wiki.ubuntu.com/DocumentationTeam). For a list of contributors, see the <ulink url="../../../common/C/contributors.xml">contributors page</ulink>

This document is made available under the Creative Commons ShareAlike 2.5 License (CC-BY-SA).

You are free to modify, extend, and improve the Ubuntu documentation source code under the terms of this license. All derivative works must be released under this license.

This documentation is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE AS DESCRIBED IN THE DISCLAIMER.

A copy of the license is available here: <ulink url="/usr/share/ubuntu-docs/common/C/ccbysa.xml">Creative Commons ShareAlike License</ulink>.

2004, 2005, 2006

The Ubuntu Documentation Project

What is a package manager?

A package manager is a program that installs and uninstalls software, and keeps track of all the components each piece of software needs.

To add or remove applications in Ubuntu, you need to use a <emphasis>package manager</emphasis>. It will automatically download the software required from the Internet and install it.

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

<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 <ulink type="help" url="ghelp:administrative">Administrative Tasks</ulink> 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 Ubuntu. These programs are stored in software archives (<emphasis>repositories</emphasis>) and are made freely available for installation over the Internet. This makes it very easy to install new programs in Linux, and it is also very secure, because each program you install is built specially for Ubuntu and checked before it is installed.

To organise the software, Ubuntu repositories are categorised 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 Ubuntu 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 website</ulink>.

Adding extra repositories

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

Be careful when installing software from third-party repositories. It may not have been tested with Ubuntu and could cause your system to break.

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

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

Add/Remove Applications

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.

Advanced package management

Several other package managers exist in Ubuntu. These contain more advanced features than <application>Add/Remove Applications</application>.

Synaptic Package Manager

To remove a package that is already installed, choose <guimenuitem>Mark for Removal</guimenuitem>.

Command-line package management with APT

To update the local list of packages, enter in a Terminal: <screen>sudo apt-get update</screen>

To install all available updates: <screen>sudo apt-get upgrade</screen>

To list other <application>apt</application> commands and options: <screen>apt-get help</screen>

Installing a single package file

It is important to ensure that any files you download come from a safe source before installing them.

This section deals with installing these single files.

Install the <application>alien</application> package.

If there is no native Ubuntu package available in any of the Ubuntu repositories, you can use the command line to install or uninstall the tarball file.

translator-credits