# Chapter 9. Managing installed applications

In Xubuntu, you don't need to download and install packages separately. Instead, you can use the software repositories to install new software. The applications and libraries are stored as packages in the repositories and they are added, removed and updated with package managers.

Xubuntu comes with two package managers installed:

- Ubuntu Software Center, a simple graphical user interface to install new software.

- apt-get, a command-line tool that can be used for advanced package management. For more information on apt-get, see the Debian apt manual.

You will need administrative access to add and remove software.

You can only use one package manager at a time. If you start another package manager while one is already open, you will receive an error message and the second package manager will not necessarily be able to function.

## Using Ubuntu Software Center

You can launch Ubuntu Software Center from → Ubuntu Software Center.

### Installing new software

- Search for an application or select a category to find an application you want to install

- From the application page, click Install

- You will be asked to enter your password; once you do that, the installation will begin

- A shortcut to your application will added to the Applications menu

To be able to install new software from the repositories, you need to be connected to the Internet.

### Removing software

- Click Installed on the top panel

- Find the application that you want to remove by using the search box or looking through the installed applications

- Select the application and click Remove

- You may be asked to enter your password; once you do that, the application will be removed

Some applications depend on others being installed in order to work properly. If you try to remove an application which is needed by another application, both of them will be removed. You will be asked to confirm that this is what you want to happen before the applications are removed.

## Additional software repositories

### Enabling more repositories

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

- Open → Settings Manager → Software & Updates or → Ubuntu Software Center → Edit → Software Sources and go to the Other Software tab

- Press Add... to add a new repository.

- Enter the APT line for the extra repository. This is available from the website of the repository in the majority of cases and it should look something like the following: `deb http://ftp.debian.org etch main`

- Press Add Source and then click Close to save your changes.

- You will be notified that the information about available software is out-of-date. Press Reload.

- Most software repositories use a GPG key to digitally sign the files they provide, which makes it easy to check that the files have not 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 Authentication tab, clicking on Import Key File, and then selecting the GPG key to be imported.

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

### Restricted and non-free software

Most of the software available for Xubuntu is free, open-source software. This software is free for anyone to install and use, and people can modify the software and redistribute it if they like. Xubuntu is built from this type of software.

Non-free software is software that is not freely redistributable or modifiable. This makes it difficult for the Xubuntu developers to improve the software and correct problems, so it is normally recommended that you use free software instead.

Restricted software is software that has restrictions on its use, preventing it from being classed as free software. Non-free software is a type of restricted software, where the restrictions are due to the software having a non-free license. Other reasons for software being classed as restricted include legal issues (use of some types of software is illegal in some countries) and patent issues (some software requires a patent license to be used legally).

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 certain video card drivers.

You should be warned by the package manager when you try to install restricted software. If the restricted software cannot be used legally in your country then there is little you can do; you should not install the software. If the software is restricted simply because it is non-free, you may choose to use it (for example, in the case of graphics card drivers). Be aware that most restricted software is not supported in Xubuntu and problems with such software often cannot be corrected by Xubuntu developers.

Sometimes it is difficult to determine why a particular software package is restricted. If this is the case, seek advice on the Ubuntu Forums. If you are still unable to determine why a package is restricted, err on the side of caution and do not install it; it may be illegal to use it in your country.

## Installing packages without an Internet connection

### Adding discs as software sources

To add a disc as a software source for your system:

- Insert a disc which contains packages; e.g., the Xubuntu installation disc which comes with a limited selection of packages

- Open → Settings Manager → Software & Updates and go to the Other Software tab

- Press the Add Volume... button; you will be prompted for your password

After adding the disc to the software sources, you will be able to install packages from the disc.

### Helpful application

If you have less than optimal Internet access, apt-offline allows you to use another computer with better access to download packages and check for package updates like security fixes. The other computer can run Xubuntu, another flavor of Ubuntu, or Debian. A graphical interface is available via apt-offline-gui that makes a complicated-looking process easy. All you need is time, patience, and a portable USB storage device. A usage example to learn more about this can be found in Chapter 10, Offline Package Management.

## Changing update frequency and behavior

You can change the frequency of the check and the way in which updates are handled. When Software Updater runs and presents you with its dialog, there is a Settings button at the bottom. Pressing this will open the Software Sources dialog at the Updates tab. Alternatively, you can access the settings dialog by going to → Settings Manager → Software & Updates and opening the Updates tab.

The following settings can be changed from this dialog:

### Update Sources

- Important security updates - Updates that fix critical security flaws are made available through this source. It is recommended that all users leave this source enabled (it should be enabled by default).

- Recommended updates - Updates that fix serious software problems (which are not security flaws) are made available through this source. Most users will want to leave this source enabled as common and annoying problems are often fixed with these updates.

The following updates should be used with some caution.

- Pre-released updates - Updates that are currently being tested before being released to everyone are provided through this update source. If you would like to help test new updates (and get fixes for problems more quickly), enable this source. Be aware that these updates may not yet be well tested; it is not recommended that you enable this source unless you are prepared to experience occasional problems.

- Unsupported updates - When new versions of popular software are released they are sometimes “backported” to an older version of Xubuntu so that users can benefit from new features and fixes for problems. These backports are unsupported, may cause problems when installed and should only be used by people who are in a real need of a new version of a software package that they know has been backported.

### Notifications of new Xubuntu versions

This section of the Software Updater deals with the way you wish future versions to be given to you. You have three options:

- For any new version - You will get notifications of all new releases, once in 6 months

- For long-term support versions - You will get notifications of new Long-term Support (LTS) releases, once in 2 years - recommended if you need maximum stability

- Never - You will not get notifications of new releases

### Other options

- Frequency of check

- Checking and installing updates automatically

- Displaying notifications about security updates

Chapter 8. Printing and Scanning |  | Chapter 10. Offline Package Management