Adding and Removing Programs and Packages
No operating system or piece of software is perfect. In addition, new features may be added that users want or need. Because of this, Ubuntu developers periodically release security and other updates to software. These updates are placed into the Ubuntu repositories and are easy to install.
Most of the updates to your machine will be security related. This means that the developers have found a weakness in a particular program in Ubuntu and have released a fix for it. There will also be a small number of updates to fix some critical bugs. For a home user, there is generally no reason not to install these updates right away, as not installing them might leave your computer open to security breaches.
When problems are discovered that could lead to security issues, like buffer overflows or remote exploits, they are fixed and released as quickly as possible, even though the danger is usually remote. Ubuntu developers also have a very strict policy about not putting new release versions of programs with significant and untested function changes or new features into stable versions of Ubuntu. This practice keeps your system more stable by not introducing new problems.
Ubuntu checks the Ubuntu repositories once a day to see if there are any new versions of software you have installed, and it tells you when you need to update your machine. If security updates exist, a pop-up window will appear. If other updates are found, they will also be made available. You can check to see if updates are available in the Gear menu at the upper right of the top panel. An entry either will say Software Up to Date or will inform you of available updates. Click either message at any time to open the program.
Ubuntu 12.04 handles package updates by launching update manager. Users are notified of security updates on a daily basis and are also notified when new Ubuntu versions are released. Because 12.04 is a Long Term Support (LTS) release, by default it will only notify of new LTS releases, meaning that it would likely be silent until April 2014. This behavior may be changed by clicking Settings at the bottom left of the Update Manager window.
Learning about What Was Updated
The update window, shown in Figure 3-18, shows you what is going to be changed. In the details pane, it shows you what got fixed and how. It might also list a Common Vulnerabilities and Exposures (CVE) number. The CVE number is a unique identifier for a security vulnerability. You can look it up on http://cve.mitre.org to see what the exact flaw was. However, most people don’t need to worry (and really don’t care) about these details.
Figure 3-18 Ubuntu Software Center main screen
Installing an Application That Is Not in the Repositories
Although the repositories contain a huge selection of packages, sometimes the package you need is not included. The first thing you should check is that you have enabled the additional repositories such as universe and multiverse. You can do this from Update Manager by clicking the Gear icon at the top right of the desktop and selecting Updates Available. Hover over Ubuntu Software Center to view its menu. Under Edit, select Software Sources to ensure that the boxes are checked for main, universe, restricted, and multiverse. (See help.ubuntu.com/community/Repositories/Ubuntu for more details.)
If you have enabled these extra repositories and your package is still not there, have a quick hunt around with a search engine to see if you can find a repository (known as a Debian or APT repository) for your package. If you find one, use the Repositories dialog box you have just played with to add the new repository, and then use Synaptic to install the package.
One common type of extra repository you may encounter is called a PPA, or personal package archive. There is good information available for using PPAs at https://help.launchpad.net/Packaging/PPA/InstallingSoftware.
If no repository is available, look for a Debian package (.deb) for the application, most likely available from the software company’s Web site, such as Adobe does with its Reader software or Skype with its VOIP software. If you find one, download it, and double-click it to install.
Finally, if all else fails, you may need to download the source code and compile it using instructions found at https://help.ubuntu.com/community/CompilingSoftware.