Introduction

Welcome to the Official Red Hat Linux Reference Guide.

The Official Red Hat Linux Reference Guide contains useful information about your Red Hat Linux system. From fundamental concepts, such as the structure of the Red Hat Linux filesystem, to the finer points of system security and authentication control, we hope you will find this book to be a valuable resource.

This guide is for you if you want to learn a bit more about how your Red Hat Linux system works. Topics that you will explore include the following:

Booting Red Hat Linux — Information about runlevels, rc.d directories, and how to start your favorite applications at boot time.
The /proc filesystem — Provides you with the kernel's view of the system.
The GRUB boot loader — A behind the scenes look at GRUB and how it boots your system.
System and network security — Find out the most common methods used by attackers to compromise your system and how to prevent security problems.
Apache directives — A look at the default Apache configuration and the options available.

Before reading this guide, you should be familiar with the contents of the Official Red Hat Linux Installation Guide concerning installation issues, the Official Red Hat Linux Getting Started Guide for basic Linux concepts and the Official Red Hat Linux Customization Guide for general customization instructions. The Official Red Hat Linux Reference Guide contains information about advanced topics that may not affect every user, depending upon how they use their Red Hat Linux system.

HTML and PDF versions of all Official Red Hat Linux manuals are available online at http://www.redhat.com/support/manuals.

Finding Appropriate Documentation

You need documentation that is appropriate to your level of Linux expertise. Otherwise, you might feel overwhelmed or not find the necessary information to answer your questions. The Official Red Hat Linux Reference Guide deals with the more technical aspects and options of your Red Hat Linux system. This section will help you decide whether to look in this manual for the information you need or consider other Red Hat Linux manuals, including online sources, in your search.

Three different categories of people use Red Hat Linux, and each of these categories require different sets of documentation and informatative sources. To help you figure out where you should start, determine your own experience level:

New to Linux: This type of user has never used any Linux (or Linux-like) operating system before or has had only limited exposure to Linux. They may or may not have experience using other operating systems (such as Windows). Is this you? If so, skip ahead to the section called Documentation For First-Time Linux Users.
Some Linux Experience: This type of user has installed and successfully used Linux (but not Red Hat Linux) before or may have equivalent experience with other Linux-like operating systems. Does this describe you? If so, turn to the section called For the More Experienced.
Experienced User: This type of user has installed and successfully used Red Hat Linux before. If this describes you, turn to the section called Documentation for Linux Gurus.

Documentation For First-Time Linux Users

For someone new to Linux, the amount of information available on any particular subject, such as printing, starting up the system or partitioning your hard drive, can be overwhelming. It helps to initially step back and gain a decent base of information centered around how Linux works before tackling these kinds of advanced issues.

Your first goal should be to obtain some useful documentation. This cannot be stressed enough. Without documentation, you will only become frustrated at your inability to get your Red Hat Linux system working the way you want.

You should acquire the following types of Linux documentation:

A brief history of Linux — Many aspects of Linux are the way they are because of historical precedent. The Linux culture is also based on past events, needs or requirements. A basic understanding of the history of Linux will help you figure out how to solve many potential problems before you actually see them.
An explanation of how Linux works — While delving into the most arcane aspects of the Linux kernel is not necessary, it is a good idea to know something about how Linux is put together. This is particularly important if you have been working with other operating systems, as some of the assumptions you currently hold about how computers work may not transfer from that operating system to Linux.
An introductory command overview (with examples) — This is probably the most important thing to look for in Linux documentation. The underlying design philosophy for Linux is that it's better to use many small commands connected together in different ways than it is to have a few large (and complex) commands that do the whole job themselves. Without examples that illustrate this approach to doing things, you may find yourself intimidated by the sheer number of commands available on your Red Hat Linux system.
Keep in mind that you do not have to memorize all of the available Linux commands. Different techniques exist to help you find the specific command you need to accomplish a task. You need only know the general way in which Linux functions, what you need to accomplish, and how to access the tool that will give you the exact instructions you need to execute the command.

The Official Red Hat Linux Installation Guide is a excellent reference for helping you get your Red Hat Linux system successfully installed and initially configured. The Official Red Hat Linux Getting Started Guide covers the history of Linux, basic system commands, GNOME, KDE, RPM, and many other fundamental concepts. You should start with these two books and use them to build the base of your Red Hat Linux knowledge. Before long, more complicated concepts will begin to make sense because you already grasp the general ideas.

Beyond reading Red Hat Linux manuals, several other excellent documentation resources are available for little or no cost:

Introduction to Linux Websites

http://www.redhat.com — On the Red Hat website, you will find links to the Linux Documentation Project (LDP), online versions of the Red Hat Linux manuals, FAQs (Frequently Asked Questions), a database which can help you find a Linux Users Group near you, technical information in the Red Hat Support Knowledge Base, and more.
http://www.linuxheadquarters.com — The Linux Headquarters website features easy to follow, step-by-step guides for a variety of Linux tasks.

Introduction to Linux Newsgroups

You can participate in newsgroups by watching the discussions of others attempting to solve problems, or by actively asking or answering questions. Experienced Linux users are known to be extremely helpful when trying to assist new users with various Linux issues — especially if you are posing your questions in the right venue. If you do not have access to a news reader application, you can access this information via the web at http://www.deja.com. Dozens of Linux-related newsgroups exist, including the following:

linux.help — A great place to get help from fellow Linux users.
linux.redhat — This newsgroup primarily covers Red Hat Linux-specific issues.
linux.redhat.install — Pose installation questions to this newsgroup or search it to see how others solved similar problems.
linux.redhat.misc — Questions or requests for help that do not really fit into traditional categories go here.
linux.redhat.rpm — A good place to go if you are having trouble using RPM to accomplish particular objectives.

Beginning Linux Books

Red Hat Linux for Dummies, 2nd Edition by Jon "maddog" Hall; IDG
Special Edition Using Red Hat Linux by Alan Simpson, John Ray and Neal Jamison; Que
Running Linux by Matt Welsh and Lar Kaufman; O'Reilly & Associates
Red Hat Linux 7 Unleashed by William Ball and David Pitts; Sams

The books suggested here are excellent primary sources of information for basic knowledge about a Red Hat Linux system. For more in-depth information concerning the various topics discussed throughout this book, many of the chapters list specific book titles, usually in an Additional Resources area.

For the More Experienced

If you have used other Linux distributions, you probably already have a basic grasp of the most frequently used commands. You may have installed your own Linux system, and maybe you have even downloaded and built software you found on the Internet. After installing Linux, however, configuration issues can be very confusing.

The Official Red Hat Linux Customization Guide is designed to help explain the various ways your Red Hat Linux system can be configured to meet specific objectives. Use this manual to learn about specific configuration options and how to put them into effect.

When you are installing software that is not covered in the Official Red Hat Linux Customization Guide, it is often helpful to see what other people in similar circumstances have done. HOWTO documents from the Linux Documentation Project, available at http://www.redhat.com/mirrors/LDP/HOWTO/HOWTO-INDEX/howtos.html, document particular aspects of Linux, from low-level kernel esoteric changes to using Linux for amateur radio station work.

Documentation for Linux Gurus

If you are a long-time Red Hat Linux user, you probably already know that one of the best ways to understand a particular program is to read its source code and/or configuration files. A major advantage of Red Hat Linux is the availability of the source code for anyone to read.

Obviously, not everyone is a C programmer, so the source code may not be helpful for you. However, if you have the knowledge and skills necessary to read it, the source code holds all of the answers.