It is hard to chart the rise of Linux over its twelve years of existence without risking the appearance of exaggeration and hyperbole. During the past five years alone, 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. Many serious analysts claim that its trajectory has just begun, and that it will eventually become the world’s most widespread operating system.
Linux was first developed by Linus Torvalds at the University of Helsinki in Finland. From his current location in Silicon Valley, Linus continues to centrally coordinate improvements. The Linux kernel continues to develop under the dedicated cultivation of a host of other programmers and hackers all over the world, joined by members of programming teams at major computer companies, all connected through the Internet.
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 a software environment with a Linux kernel along with a large set of applications and other software components. In this larger meaning, many people prefer the term GNU/Linux, which acknowledges the central role played by tools from the Free Software Foundation’s GNU project in the development of the kernel.
Linux systems cannot be technically referred to as a “version of Unix,” as they have not undergone the required tests and licensing. However, Linux offers all the common programming interfaces of 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.
The historical impact of Linux goes beyond its role as a challenge to all versions of Unix as well as Microsoft Windows, particularly on servers. Linux’s success has also inspired countless other free software or open source (defined at http://opensource.org) projects, including Samba, GNOME, and a mind-boggling collection of innovative projects that you can browse at numerous sites like SourceForge (http://sourceforge.net). As both a platform for other developers and a development model, Linux gave a tremendous boost to the GNU project, and has also become a popular platform for Java development. 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 Other Resources in the preface.
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 and be assured of fewer crashes; even its security is better than many commercial alternatives.
Linux first appeared in organizations as ad hoc installations by hackers running modest web servers or development systems at universities and research institutions, but now extends deeply into corporations around the world. People deploying Linux for mission-critical systems tend to talk about its ample practical advantages, such as the ability to deliver a lot of bang for the buck and the ease of deploying other powerful tools on Linux such as Apache, Samba, and Java environments. They also cite Linux’s ability to grow and sprout new features of interest to large numbers of users. But these advantages can be traced back to the concept of software freedom, which is the root of the broad wave of innovation driving Linux.
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 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 programmers 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 brings back the spirit of working together—all the more so because the Internet is now so widespread. And for the many who are too young to remember the first round of open systems or whose prior experience has been constricted by trying to explore and adapt proprietary operating systems, now is the time to discover the wonders of freely distributable source code and infinitely adaptable interfaces.
The economic power behind Linux’s popularity is its support for an enormous range of hardware. 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: Linux 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. Embedded versions of the Linux kernel are in growing use because, although they are larger than the most stripped-down operating systems, they deliver a range of powerful features within a remarkably small footprint.
Opinions still differ on how suitable Linux is as a general-purpose desktop system. But the tremendous advances in usability and stability of the desktop software and its applications are undisputed. Soon (if not today), one will find Linux in many offices and other end-user environments. Meanwhile, the strides made by Linux in everyday computing tasks are reflected in the new audio and CD-related commands found in this edition.
 Before an operating system can be called “Unix,” it must be branded by The Open Group.