Using a third-party package: If your distribution's package manager doesn't offer the software you want, you might still find a third-party package in a downloadable file. Most files with a .deb extension will work under Ubuntu. Double-clicking them from a file browser should bring up the built-in package installer, as shown here.
Sooner or later, we all end up installing new software on our computers. Whether it's a new version of Firefox, or a cool game, or a video editing package, there comes a time when you want to make your system do more than it can do now.
Under Linux, installing new applications isn't a particularly hard task, but installations do come in several different varieties, so it's worth understanding the differences and what you'll need to know to make them work.
Option 1: Use the built-in package manager
The easiest way to get new software onto a Linux system is to use the integrated package management system that is included with your distribution. You can use the package manager to download thousands of software packages that have been pre-built and tested for your specific version of Linux.
In Linux, software packages are usually equivalent to applications, although an application may in fact consist of several packages. For example, a graphics editor app may be made up of a package with the main program, a package with the documentation, and a package with the system libraries that the application needs to run.
One advantage of using an integrated package manager is that it will usually download and install all the related packages that your chosen package depends on. With a live Internet connection, you can download everything you need in one operation.
Another advantage to using the built-in package manager is that the system will periodically check for upgrades to your newly installed package(s), which means that they will stay up to date -- although as mentioned below, "up to date" is a relative concept with packages.
The package management system used in Debian-based distributions (including Ubuntu) is called the Synaptic Package Manager and is found under the System menu. If you know the name of the package you want to install, you can also install it from the command line by typing
sudo apt-get install packagename
where packagename is the name of your chosen software package. Be aware that the names can be a little quirky.
Red Hat-based distributions (including Fedora) use a system called PackageKit under the covers. You can get to the graphical front end by going to the System menu, clicking on Administration, and then Add/Remove Program. From the command line, you use:
sudo yum install packagename
Some commercial Linux distributions, such as Xandros, have created integrated package managers that double as storefronts to sell you commercial software. You may need to scroll down a bit to see the free software available for the distribution, but you should be able to find it in short order.
The biggest disadvantage of using a built-in package manager is that the software you want may not be there. For an application to appear in the list of available options, some benevolent party involved in the distribution you're running has to build and package the software you want in the form you need and for the version of Linux you're using. If you're using an obscure distribution, or unpopular software, the software may be just unavailable altogether.
The second problem is that the packaged versions of software found in distribution repositories tend to lag a bit from the latest versions. This is mainly because packages have to be built and tested by the distribution maintainers before they're allowed into the official software repositories for the distributions. So you might be installing a two-month-old version of the GIMP rather than the current one. Some distributions allow new versions of packages to be added only when there's a new version of the distribution itself, which can mean that the packages available could be very out of date indeed.