Linux is a UNIX-like kernel, which is written by Linus Torvalds and other developers. Linux runs on many different architectures, for example on IA32, IA64, Alpha, m68k, SPARC and PowerPC machines. The latest kernel and information about the Linux kernel can be found on the Linux kernel website: http://www.kernel.org.

The Linux kernel is often confused with the GNU/Linux operating system. Linux is only a kernel, not a complete operating system. GNU/Linux consists of the GNU operating system with the Linux kernel. The following section gives a more extensive description of GNU/Linux.

In 1984 Richard Stallman started an ambitious project with the goal to write a free UNIX-like operating system. The name of this system is GNU, which is an acronym of “GNU's Not UNIX”. Around 1990, all major components of the GNU operating system were written, except the kernel. Two years earlier, in 1988, it was decided that the GNU project would use the Mach 3.0 microkernel as the foundation of its kernel. However, it took until 1991 for Mach 3.0 to be released under a free software license. In the the same year Linus Torvalds started to fill the kernel gap in the GNU system by writing the Linux kernel. GNU/Linux thus refers to a GNU system running with the Linux kernel.

The GNU kernel, named “HURD” was still under development when this book was written, and is available as the GNU/HURD operating system. There are some other kernels that are ported to the GNU operating system as well. For instance, the Debian project has developed a version of the GNU operating system that works with the NetBSD kernel.

Slackware Linux is a GNU/Linux distribution, which is maintained and developed by Patrick Volkerding. A distribution is a coherent collection of software that provides a usable GNU/Linux system. Volkerding started using GNU/Linux because he needed a LISP interpreter for a project. At the time the dominant GNU/Linux distribution was Softlanding System Linux (SLS Linux). Slackware Linux started out as a private collection of Volkerding's patches for SLS Linux. The first publicly available Slackware Linux release was 1.0, which was released on July 16, 1993.

In contrast to many other GNU/Linux distributions, Slackware Linux adheres to the so-called KISS (Keep It Simple Stupid) principle. This means that Slackware Linux does not have complex graphical tools to configure the system. As a result the learning curve of Slackware Linux can be high for inexperienced GNU/Linux users, but it provides more transparency and flexibility. Besides that you get a deeper understanding of GNU/Linux with no-frills distributions like Slackware Linux.

Another distinguishing aspect of Slackware Linux, that also “complies” with the KISS principle, is the Slackware Linux package manager. Slackware Linux does not have a complex package manager like RPM or dpkg. Packages are normal tgz (tar/gzip) files, often with an additional installation script and a package description file. For novice users tgz is much more powerful than RPM, and avoids dependency problems. Another widely known feature of Slackware Linux is its initialization scripts. In contrast to most other GNU/Linux distributions Slackware Linux does not have a directory for each runlevel with symbolic links to services that have to be started or killed in that runlevel. It uses a simpler approach in which you can enable or disable services by twiddling the executable bit of an initialization script.

The packages in Slackware Linux are compiled with as little modifications as possible. This means you can use most general GNU/Linux documentation.

Since GNU/Linux is a free reimplementation of the UNIX operating system, it is a good idea to look at the philosophy that made UNIX widely loved. Doug McIlroy summarized the UNIX philosophy in three simple rules:

Odds are that you do not intend to write programs for GNU/Linux. However, even as a user these basic UNIX rules can mean a lot to you. Once you get to know the essential commands that have been part of UNIX for many years, you will be able to combine simple programs to solve complex problems. Keep this in mind while you learn Slackware Linux; try to get a feeling for how you can divide complex tasks in simple combined operations.

Most packages in Slackware Linux are published under a free software or open source license. Under these licenses software may be used, studied, changed and distributed freely. Practically, this means that the software is available and redistributable in source and binary form. Although the free software and open source software movements share many licenses and principles, there are subtle differences between both movements. The open source movement tends to focus on the economic and technical advantages of sharing source code, while the free software movement puts accent on the ethical side of providing sources and binaries freely. As the GNU website puts it: “Free software is a matter of liberty, not price. To understand the concept, you should think of free as in free speech, not as in free beer.^[1]” In the spirit of free and open source software the source code of almost all packages is included in the official Slackware Linux CD set or DVD.

Slackware Linux is freely downloadable from the official Slackware Linux mirrors. The list of Slackware mirrors is available at http://www.slackware.com/getslack/.

You can also order Slackware Linux as a CD set or DVD from the Slackware Store. Many Internet shops also provide Slackware Linux cheaply on CD-ROM or DVD, but you are only supporting Slackware Linux financially if you buy an official CD set or DVD. The Slackware Store also offers Slackware Linux subscriptions. A subscriber automatically receives new Slackware Linux releases at a reduced price.

If you would like to have more information about purchasing Slackware Linux, visit the Slackware Store website at http://store.slackware.com/.