Chapter1.Overview

Chapter 1. Overview

In this chapter

• 1.1 History of UNIX 2

• 1.2 Standards and Common Interfaces 4

• 1.3 Free Software and Open Source 5

• 1.4 A Quick Survey of Linux Distributions 5

• 1.5 Kernel Release Information 8

• 1.6 Linux on Power 8

• 1.7 What Is an Operating System? 9

• 1.8 Kernel Organization 11

• 1.9 Overview of the Linux Kernel 11

• 1.10 Portability and Architecture Dependence 26

• Summary 27

• Exercises 27

Linux is an operating system that came into existence as the hobby of a student named Linus Torvalds in 1991. The beginnings of Linux appear humble and unassuming in comparison to what it has become. Linux was developed to run on machines with x86 architecture microprocessors with AT hard disks. The first release sported a bash shell and a gcc compiler. Portability was not a design concern at that time, nor was widespread use in academia and industry its vision. There was no business plan or vision statement. However, it has been available for free from day one.

Linux became a collaborative project under the guidance and maintenance of Linus from the early days of beta versions. It filled a gap that existed for hackers wanting a free operating system that would run on the x86 architecture. These hackers began to contribute code that provided support for their own particular needs.

It is often said that Linux is a type of UNIX. Technically, Linux is a clone of UNIX because it implements the POSIX UNIX Specification P1003.0. UNIX has dominated the non-Intel workstation scene since its inception in 1969, and it is highly regarded as a powerful and elegant operating system. Relegated to high-performance workstations, UNIX was only available at research, academic, and development institutions. Linux brought the capabilities of a UNIX system to the Intel personal computer and into the homes of its users. Today, Linux sees widespread use in industry and academia, and it supports numerous architectures, such as PowerPC.

This chapter provides a bird's eye view of the concepts that surround Linux. It takes you through an overview of the components and features of the kernel and introduces some of the features that make Linux so appealing. To understand the concepts of the Linux kernel, you need to have a basic understanding of its intended purpose.