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Introduction

 Welcome to the Red Hat Enterprise Linux Introduction to System Administration. The Red Hat Enterprise Linux Introduction to System Administration contains introductory information for new Red Hat Enterprise Linux system administrators. It does not teach you how to perform a particular task under Red Hat Enterprise Linux; rather, it provides you with the background knowledge that more experienced system administrators have learned over time. This guide assumes you have a limited amount of experience as a Linux user, but no Linux system administration experience. If you are completely new to Linux in general (and Red Hat Enterprise Linux in particular), you should start by purchasing an introductory book on Linux. Each chapter in the Red Hat Enterprise Linux Introduction to System Administration has the following structure: Generic overview material -- This section discusses the topic of the chapter without going into details about a specific operating system, technology, or methodology. Red Hat Enterprise Linux-specific material -- This section addresses aspects of the topic related to Linux in general and Red Hat Enterprise Linux in particular. Additional resources for further study -- This section includes pointers to other Red Hat Enterprise Linux manuals, helpful websites, and books containing information applicable to the topic. By adopting a consistent structure, readers can more easily read the Red Hat Enterprise Linux Introduction to System Administration in whatever way they choose. For example, an experienced system administrator with little Red Hat Enterprise Linux experience could skim only the sections that specifically focus on Red Hat Enterprise Linux, while a new system administrator could start by reading only the generic overview sections and using the Red Hat Enterprise Linux-specific sections as an introduction to more in-depth resources. While on the subject of more in-depth resources, the System Administrators Guide is an excellent resource for performing specific tasks in a Red Hat Enterprise Linux environment. Administrators requiring more in-depth, factual information should refer to the Reference Guide. HTML, PDF, and RPM versions of the manuals are available on the Red Hat Enterprise Linux Documentation CD and online at http://www.redhat.com/docs/manuals/enterprise/.

1. Architecture-specific Information

 Unless otherwise noted, all information contained in this manual apply only to the x86 processor and processors featuring the Intel® Extended Memory 64 Technology (Intel® EM64T) and AMD64 technologies. For architecture-specific information, refer to the Red Hat Enterprise Linux Installation Guide for your respective architecture.

 2. Document Conventions

 This manual uses several conventions to highlight certain words and phrases and draw attention to specific pieces of information. In PDF and paper editions, this manual uses typefaces drawn from the Liberation Fonts set. The Liberation Fonts set is also used in HTML editions if the set is installed on your system. If not, alternative but equivalent typefaces are displayed. Note: Red Hat Enterprise Linux 5 and later include the Liberation Fonts set by default. Introduction 11

 2.1. Typographic Conventions

 Four typographic conventions are used to call attention to specific words and phrases. These conventions, and the circumstances they apply to, are as follows.

 Mono-spaced Bold 

Used to highlight system input, including shell commands, file names and paths. Also used to highlight keys and key combinations. For example: To see the contents of the file my_next_bestselling_novel in your current working directory, enter the cat my_next_bestselling_novel command at the shell prompt and press Enter to execute the command. The above includes a file name, a shell command and a key, all presented in mono-spaced bold and all distinguishable thanks to context. Key combinations can be distinguished from an individual key by the plus sign that connects each part of a key combination. For example: Press Enter to execute the command. Press Ctrl+Alt+F2 to switch to a virtual terminal. The first example highlights a particular key to press. The second example highlights a key combination: a set of three keys pressed simultaneously. If source code is discussed, class names, methods, functions, variable names and returned values mentioned within a paragraph will be presented as above, in mono-spaced bold. For example: File-related classes include filesystem for file systems, file for files, and dir for directories. Each class has its own associated set of permissions.

 Proportional Bold

 This denotes words or phrases encountered on a system, including application names; dialogue box text; labelled buttons; check-box and radio button labels; menu titles and sub-menu titles. For example: Choose System → Preferences → Mouse from the main menu bar to launch Mouse Preferences. In the Buttons tab, select the Left-handed mouse check box and click Close to switch the primary mouse button from the left to the right (making the mouse suitable for use in the left hand). To insert a special character into an edited file, choose Applications → Accessories → Character Map from the main menu bar. Next, choose Search → Find… from the Character Map menu bar, type the name of the character in the Search field and click Next. The character you sought will be highlighted in the Character Table. Double-click this highlighted character to place it in the Text to copy field and then click the Copy button. Now switch back to your document and choose Edit → Paste from the edit menu bar. The above text includes application names; system-wide menu names and items; application-specific menu names; and buttons and text found within a GUI interface, all presented in proportional bold and all distinguishable by context. Mono-spaced Bold Italic or Proportional Bold Italic Red Hat Enterprise Linux 4 Introduction To System Administration 12 Whether mono-spaced bold or proportional bold, the addition of italics indicates replaceable or variable text. Italics denotes text you do not input literally or displayed text that changes depending on circumstance. For example: To connect to a remote machine using ssh, type ssh username@domain.name at a shell prompt. If the remote machine is example.com and your username on that machine is John, type ssh john@example.com. The mount -o remount file-system command remounts the named file system. For example, to remount the /home file system, the command is mount -o remount /home. To see the version of a currently installed package, use the rpm -q package command. It will return a result as follows: package-version-release. Note the words in bold italics above — username, domain. name, file-system, package, version and release. Each word is a placeholder, either for text you enter when issuing a command or for text displayed by the system. Aside from standard usage for presenting the title of a work, italics denotes the first use of a new and important term. For example: Publican is a DocBook publishing system.

 2.2. Pull-quote Conventions

 Terminal output and source code listings are set off visually from the surrounding text. Output sent to a terminal is set in mono-spaced roman and presented thus