Introduction

Welcome to Absolute BSD! This book is a one−stop shop for new UNIX administrators who want to build, configure, and manage dedicated FreeBSD servers. It will also be useful for those folks who want to run FreeBSD on their desktop or combined desktop/server systems.

By the time you finish this book, you should be able to use FreeBSD to provide network services. You should also understand how to manage, patch, and maintain your FreeBSD systems, and have a basic understanding of networking, system security, and software management. We will discuss FreeBSD version 4, which is the version recommended for production use as this book is being released. Most of this book will be applicable to earlier and later versions, as well. Much of this book is also applicable to NetBSD and OpenBSD.

What Is FreeBSD?

FreeBSD is a UNIX−like operating system,[1] available freely over the Internet, that is used extensively in the ISP (Internet service provider) world, embedded devices, and anywhere reliability is paramount. It's based directly on the original UNIX produced by AT&T in the 1970s.

Many years ago AT&T needed a lot of computer software to run their business. They were not allowed to compete in the computer business, however. As a result, they licensed various pieces of software, and the source code for it, to universities at low, low prices. University students with access to this nifty technology could read the source code to learn how it worked. In return, AT&T got free exposure, some pocket change, and a generation of computer scientists who cut their teeth on their equipment. Everyone was happy. The best−known software distributed under this licensing plan was UNIX.

[1]Why UNIX−like? Well, the word UNIX is a trademark that belongs to The Open Group. For an operating system to be certified "UNIX," someone must pay The Open Group large chunks of money. Since FreeBSD is developed in a not−for− profit manner, this isn't likely.

How Did FreeBSD Get Here?

Compared with modern operating systems, the original UNIX wasn't very good. But, since so many students had the source code for UNIX, and so many teachers needed projects for their students, UNIX was quickly improved by their efforts. Gradually, useful commands were built. The ability to control running programs (also known as job control) was added. A filesystem appeared that supported features we take for granted now. Over many years, entire chunks of the original UNIX operating system were extracted and replaced.

The various universities that worked on UNIX shared their improvements and enhancements, with the Computer Systems Research Group (CSRG) at the University of California, Berkeley, acting as a central clearinghouse for UNIX code improvements. The CSRG distributed this code for free to anyone with a valid AT&T UNIX license.

The resulting collection of patches for UNIX came to be known as the Berkeley Software Distribution, or BSD UNIX. (It didn't hurt Berkeley's status any that the Defense Advanced Research Projects Agency (DARPA) contributed funding to the CSRG to implement TCP/IP in UNIX.)

This development process continued for a long, long time. In fact, if you look at the copyright statement on FreeBSD, you'll see this:

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Copyright 1979, 1980, 1983, 1986, 1988, 1989, 1991, 1992, 1993, 1994

The Regents of the University of California. All rights reserved.

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Yep, 15 years of work—a lifetime in software development. In fact, so much development went into the original UNIX that the CSRG found that over the years they had replaced almost all of UNIX with code created by the CSRG and their contributors. What remained of AT&T's work was actually pretty small.

The BSD License: BSD Goes Public

Eventually, the CSRG's funding started running out. After some political wrangling within the University of California, in 1992 the code was released to the general public under what became known as the BSD license. Today, the BSD license has three clauses that can be summarized as follows:

∙Don't claim you wrote this.

∙Don't blame us if it breaks.

∙Don't use our name to promote your product.

(The original license required that every time someone used the software, they had to include a notice that it included software copyrighted by the University of California. This requirement was dropped a few years later. Today, people can use BSD code without having to announce it or notify anyone.)

The BSD license may be the most liberal software license ever used. People are free to take BSD and include it in proprietary products, free products, and open−source products, or print it out on punch cards and cover the lawn with it. Instead of "copyright," the BSD license is sometimes referred to as "copy− center," as in "take this down to the copy center and run off a few for yourself." Not surprisingly, companies such as Sun Microsystems jumped right on it because, well, it was free.

The Birth of Modern FreeBSD

During the CSRG's heyday, however, UNIX work proceeded apace at AT&T. AT&T took parts of the BSD UNIX distribution and integrated them with their UNIX, then turned around and relicensed the result.

This worked well for AT&T until the grand breakup, when the mother of all telephone companies suddenly was permitted to compete in the software business. They had one particularly valuable property: a high−end operating system that had been extensively debugged by thousands of people all over the world. They happily started selling UNIX to enterprises and charging very high fees for it, all the while maintaining the university relationships that had given them such an advanced operating system.

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