Chapter 1. Introduction

Table of Contents
The Linux Kernel
The Unix Filesystem
The Shell

``Operating system'' (OS) is the name given to the set of programs that controls a computer's hardware and software, and that interacts with the user. This Guide is about using a computer running the GNU/Linux OS. It assumes a fairly new PC and an up-to-date OS installation. Typical GNU/Linux distributions (distros) are Debian Woody and RedHat 7.x, 8, or 9.

In this guide, ``unix'' is used as a generic term to apply to all UNIX-type operating systems. All examples are based on GNU/Linux systems. While most of these commands will work on other unix systems such as Sun Solaris, BSD, HP-UX, Mac OS/X, and IBM's AIX, there are often differences between them and GNU/Linux in the syntax of switches and the appearance of the output.

The unix operating system has three main components:

The Linux Kernel

The kernel is the core part of the operating system. It is the part that loads first, and it stays resident in memory as long as the computer is powered on and running.

The key functions of the kernel include:

On a typical GNU/Linux system, the kernel is stored in a file named /boot/vmlinux or /boot/vmlinuz. This file is loaded into memory when the computer boots.