Thursday, August 18, 2011

How Fedora Installs Software

In the Windows world, there is usually one way to install software: clicking on an installation application that starts up and runs the whole setup for you from start to finish.

In Fedora, like most Linux distributions, there are three methods of software installation. Admittedly, one way to install sure sounds attractive and less confusing, but the one-size-fits-all installation service comes with a potentially bad price: Windows installation routines can often overwrite important underpinnings in the operating system for the sake of the application that’s currently being installed. This is good for your installed application, but potentially very bad for any pre-existing application on your system that was using that same section of Windows’ code.

In Fedora, all of the three installation methods take great pains to install applications using only what’s already in Fedora. If what the application needs is not installed in Fedora already, it has what is known as a dependency. The installing user (that would be you) will be told about any dependencies and asked how to proceed. A description of the three installation methods is easy to provide:

» Self-Contained Installation Program. This methodology is very much like the method used by Windows. A special installation application is run that automagically handles the application’s setup on your PC. This type of installation is not common on Fedora machines, though some of the larger consumer applications ( or Firefox) can be installed in this manner. There is one important difference from Windows: no existing software is changed by the installation application. Dependencies are usually handled well, but it’s not foolproof.

» Compiled from Source. Remember how any user can get to the source code of any free software application? Well, once you have that code, you can perform what’s known as a compilation to turn that code (which only humans, at least the smart ones, can read) into something the PC can read and work with. Software compilation isn’t hard, but it is time-consuming at times, and dependencies are not automatically handled.

» Package Management. This method is unique to UNIX-based systems. All of the files and settings needed to install and run an application are included in one package. Fedora uses RPM-based, or .rpm, packages. (Other Linux distributions, such as Debian or Ubuntu, use Debian-based, or .deb, packages.)

As you may have guessed, package management is the preferred method of software installation in Fedora. Package installation is actually performed by an application known as a package manager. It helps keep track of all of the applications that are already installed on your PC and also helps keep track of those dependencies we mentioned. If you install a package that needs some additional software tools to properly operate on your Fedora system, it’s the package manager that will figure out what other packages you need.

In Fedora, there are actually three package managers that will assist you in your installation needs:

» PackageKit. This robust graphical package manager lists every package available for Fedora, which lets you search for software applications from a very big list. Applications are categorized by type, status on your system (installed or not), or origin.

» Software Update. Another graphical tool, this package manager has one job to do: keep your system as up to date as possible. If there’s a new version of any of your installed applications out there, Software Update will know about it and flag it for you to download and install.

» yum. The core package manager for Fedora, this command line application makes getting new packages as easy as typing one line of text and pressing the Enter key.

Each of these three package managers is configured to find all of the packages from Fedora’s package repositories. In the next section, we’ll walk through repositories and how they work.

Source of Information : Cengage-Introducing Fedora 2010

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