## 0.3. Conventions Used in This Book

The following is a list of the typographical conventions used in this book:

Bold | is used for machine names, hostnames, usernames, and IDs.
Italic | is used for file and directory names, program and command names, command-line options, email addresses and pathnames, site names, and new terms.
`Constant Width` | is used in examples to show the contents of files or the output from commands, to indicate environment variables and keywords that appear in code, and for Emacs commands.
Constant Italic | is used to indicate variable options, keywords, or text that the user is to replace with an actual value.
`Constant Bold` | is used in examples to show commands or other text that should be typed literally by the user.

The bomb icon in the left margin is for Caution: you can make a mistake here that disables or damages your system or is hard to recover from.

The book icon indicates a reference to another part of this book or to another source of information. The citation string (or strings) underneath the book may be a number and key for a book, HOWTO article, or RFC listed in the Bibliography; a pointer to another chapter or appendix in this book; or a referral to a particular program's manual page.

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