UNIX For Dummies [Electronic resources] نسخه متنی

What’s Old, What’s New

The original guts of Linux were written from scratch by Linus Torvalds and have since been greatly changed and extended by other people. He based Linux more or less on System V (on descriptions of System V; there’s no code from System V). Most programs that people actually use (the shells and other commands) come either from 4.4BSD or from the GNU project, which modeled most of them after the Berkeley UNIX versions, so most of the commands are BSD-ish. Because the networking programs are adapted from the Berkeley ones, they also are all BSD-ish.

Technically speaking, Linux refers only to the operating system “kernel.” When most people refer to a Linux system, though, they usually mean the whole package: operating system plus the GNU programs that come with it. Like all UNIX systems, Linux systems can run various shells, editors, and other software. Most versions of Linux use BASH as the default shell because it’s also new and snazzy.

Linux is made available under the GNU General Public License (GPL), Version 2, the same license the Free Software Foundation uses for most of its programs. The license has seven pages of legalese, much of which is about where copyright notices have to appear and stuff like that, but the basic plan is simple. In short, it says:

You can copy and distribute Linux and other GPL software, and you can charge for it.

But, anyone to whom you distribute it has the right to give copies away for free.

And you must include the source code (or make it available for no more than a reproduction fee) in the distribution.

The idea is that people are permitted, even encouraged, to distribute copies of GPL software and to sell maintenance service, as long as the software itself remains freely available.

Don’t confuse free software with shareware, which is software for which you are supposed to pay the original author if you use it, or with public domain software, with which you can do anything you want.

Although the GPL was subject to considerable debate and a fair amount of ridicule when it first came out in about 1990, it has worked pretty much the way its authors intended — GPL software (including Linux) is widely available, and people do indeed constantly work on and improve it.

Remember Keep in mind that because Linux is a moving target, with frequent improvements to the programs, the version of Linux you use is probably not exactly the same as the version described in any book, including this one. At the time we wrote this edition of this book, the latest stable version of Linux was 2.5.75, but even if you have a more recent version, the basic structure is the same.

A look at the various Web sites and Usenet newsgroups dedicated to Linux shows a veritable flurry of Linux-related activity. New programs, extensions, and enhancements for Linux appear daily, it seems. Red Hat Linux, for example, now offers a range of snazzy new products, including a secure Web server, several Microsoft Office-like suites of desktop tools including ApplixWare and OpenOffice.org, and fully graphical integrated desktops (see Chapter 4 for details about UNIX desktops).

Several organizations have set up computer clusters — hundreds of computers acting like one enormous supercomputer — built out of ordinary Linux systems connected by fast Ethernets. You can get the source code, operating system, and management tools to set up such a cluster off the Internet for free (at www.beowulf.org ). Or if you want all your computing in one place, you can buy a multi-million dollar IBM mainframe computer and run Linux on it, too.

The name Linux is derived from the first name of its creator, Linus Torvalds. The “Line-ucks” group holds that the pronunciation is based on the usual English pronunciation of Linus. Linus Torvalds himself, though, a Swedish-speaking Finn, has helpfully provided an audio file on the Internet in which he provides the definitive answer in both English and Swedish. In the file, he says, “Hello, this is Lee-noos Torvalds, and I pronounce Lee-nooks as Lee-nooks.” It’s up to you whether you want to say “Linux” with a Swedish accent, but to our ears his reading sounds much closer to the Anglicized “Linn-ucks,” so that’s what we use.

Tip In Chapter 14, we talk about the latest releases of the most popular versions of Linux. In Chapter 26, we describe a number of ways you can get additional information about Linux, including reading one of a number of Usenet newsgroups about Linux or subscribing to a Linux magazine.