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Chapter 1. Introduction


The Excitement of Linux
Distribution and Support
Commands on Linux
What This Book Offers
Sources and Licenses
Beginner's Guide

In just a few years, Linux has grown from a student/hacker playground to an upstart challenger in the server market to a well-respected system taking its rightful place in educational and corporate networks. A freely redistributable clone of the Unix operating system, Linux is turning up everywhere. People use it for web servers, file servers, and workstations instead of--or alongside -- systems from traditional Unix vendors as well as Windows NT. In addition to its role in large networks (because it's a friendly fellow that fits in very nicely with other operating systems), Linux is popular among Windows users who just want to try something that gives them more speed, more power, and more control.

The historical impact of Linux goes even beyond its own penetration into the markets of proprietary operating systems. Its success has inspired countless other free software or open source (, including Samba, GNOME, and a mind-boggling collection of innovative projects that you can browse at numerous sites like SourceForge ( both a platform for other developers and a development model, Linux gave a tremendous boost to the Free Software Foundation's GNU project, which in turn had furnished key software that made the development of Linux possible. In short, Linux is a central participant in the most exciting and productive free software movement ever seen.

If you haven't obtained Linux yet or have it but don't know exactly how to get started using it, see the Preface.

1.1. The Excitement of Linux

Linux is first of all free software: anyone can download the source from the Internet or buy it on a low-cost CD-ROM. But Linux is becoming well known because it's more than free software -- it's unusually good software. You can get more from your hardware with Linux (particularly on Intel systems, where it was originally developed) and be assured of fewer crashes; even its security is better than many commercial alternatives.

As free software, Linux revives the grand creativity and the community of sharing that Unix was long known for. The unprecedented flexibility and openness of Unix--which newcomers usually found confusing and frustrating but which they eventually found they couldn't live without -- continually inspired extensions, new tools like Perl, and experiments in computer science that sometimes ended up in mainstream commercial computer systems.

Many fondly remember the days when AT&T provided universities with Unix source code at no charge, and the University of Berkeley started distributing its version in any manner that allowed people to get it. For these older hackers, Linux can bring back the spirit of working together -- all the more so because the Internet is now widespread. And for the many who are too young to remember the first round of open systems (such as the hordes of students attracted to Linux) or whose prior experience has been woefully constricted by proprietary operating systems, now is the time to discover the wonders of freely distributable source code and infinitely adaptable interfaces.

The Linux kernel itself was originally designed by Linus Torvalds at the University of Helsinki in Finland and later developed through collaboration with countless volunteers worldwide. By "kernel," we mean the core of the operating system itself -- not the applications (such as the compiler, shells, and so forth) that run on it. Today, the term "Linux" is often used to mean the kernel as well as the applications and complete system environment.

Most Linux systems cannot be technically referred to as a "version of Unix," as they have not been submitted to the required tests and licensed properly.[1]However, at least one Linux distribution has in fact been branded as POSIX.1. Linux offers all the common programming interfaces as standard Unix systems, and as you can see from this book, all the common Unix utilities have been reimplemented on Linux. It is a powerful, robust, fully usable system for those who like Unix.

[1] Before an operating system can be called "Unix," it must be branded by X/Open.

The economic power behind Linux's popularity is its support for an enormous range of hardware used with IBM-compatible personal computers. People who are accustomed to MS-DOS and Microsoft Windows are often amazed at how much faster their hardware appears to work with Linux -- it makes efficient use of its resources.

For the first several years, users were attracted to Linux for a variety of financial and political reasons, but soon they discovered an unexpected benefit: it works better than many commercial systems. With the Samba file and print server, for instance, Linux serves a large number of end-user PCs without crashing. With the Apache web server, it provides more of the useful features web administrators want than competing products do.

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