Monday, January 31, 2011

What Is a Distribution?

It’s clear to most people that Ubuntu is an OS. The full story is a little more complex. Ubuntu is what is called a distribution of GNU/Linux—a distro for short. Understanding exactly what that means requires, once again, a little bit of history. In the early days of GNU and Linux, users needed a great deal of technical knowledge. Only geeks needed to apply. There were no Linux operating systems in the sense that we usually use the term there was no single CD or set of disks that one could use to install. Instead, the software was dozens and even hundreds of individual programs, each built differently by a different individual, and each distributed separately. Installing each of the necessary applications would be incredibly time consuming at best. In many cases, incompatibilities and the technical trickery necessary to install software made getting a GNU/Linux system on a hard disk prohibitively difficult. A great deal of knowledge of configuration and programming was necessary just to get a system up and running. As a result, very few people who were not programmers used these early GNU/Linux systems.

Early distributions were projects that collected all of the necessary pieces of software from all of the different places and put them together in an easier-to-install form with the most basic configuration already done. These distributions aimed to make using GNU/Linux more convenient and to bring it to larger groups of users. Today, almost nobody uses GNU/Linux without using a distribution. As a result, distribution names are well known. Ubuntu is such a project. Other popular distros include Red Hat and Fedora, Novell’s SUSE, Gentoo, and of course Debian.

Most distributions contain a similar collection of software. For example, they all contain most of the core pieces of GNU and a Linux kernel. Almost all contain the X Window System and a set of applications on top of it that may include a Web browser, a desktop environment, and an office suite. While distributions started out distributing only the core pieces of the OS, they have grown to include an increasingly wide array of applications as well. A modern distribution includes all of the software that “comes with an OS,” that is, several CDs or DVDs containing anything that most users might want and that the distribution is legally allowed to distribute.

Ubuntu, like other contemporary distros, offers a custom installer, a framework including software and servers to install new software once the system has been installed, a standard configuration method through which many programs can be configured, a standard method through which users can report bugs in their software, and much more. Frequently, distributions also contain large repositories of software on servers accessible through the Internet. To get a sense of scale, Ubuntu includes more than 30,000 pieces of software on its central servers—each piece of software is customized slightly and tested to work well with all of the other software on the system. That number grows daily.

What’s important to realize is that the creators of distributions do not, for the most part, write or create the applications you use. The Ubuntu team did not write Linux, and it did not write GNU—although individuals on the team have contributed to both projects. Instead, the Ubuntu team takes GNU, Linux, and many thousands of other applications and then tests and integrates them to be accessible under a single installer. Ubuntu is the glue that lets you take a single CD, install hundreds of separate pieces of software, and have them work together as a single, integrated desktop system. If you were to pick up a CD of another distribution such as Debian, Red Hat, or Novell, the software installed would be nearly identical to the software in Ubuntu. The difference would be in the way the software is installed, serviced, upgraded, and presented and the way it integrates with other pieces of software on the system.

Source of Information :  Prentice Hall The official Ubuntu Book 5th Edition 2010   
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