Conventions Used in This Book

We use both typography and common Unix documentation conventions to give you additional information in the text.

Typographic Conventions

Plain text

Indicates menu titles, menu options, menu buttons, and keyboard accelerators (such as Alt and Ctrl).

Italic

Indicates new or technical terms, system calls, URLs, hostnames, email addresses, filenames, file extensions, pathnames, and directories.

Constant width

Indicates commands, options, switches, variables, attributes, keys, functions, types, objects, HTML tags, macros, the contents of files, or the output from commands.

Constant width bold

Shows commands or other text that should be typed literally by the user.

Constant width italic

Shows text that should be replaced with user-supplied values.

This icon signifies a tip, suggestion, or general note.

This icon indicates a warning or caution.

There are times when it is very important to pay attention to the typography because it distinguishes between two similarly named, but different concepts. For example, the host command and the /etc/hosts file, or the jail(2) system call versus the jail(8) command. Sometimes the typeface is an important clue to help you remember which one we're referring to in a given context.

Conventions in Examples

You will see two different prompts in the examples we give for running commands. We follow the time-honored Unix convention of using % to represent a non-root shell (e.g., one running as your normal user ID) and # to represent a root-equivalent shell. Commands that appear after a % prompt can (and probably should) be run by an unprivileged user. Commands that appear after a # prompt must be run with root privileges. Example P-1 shows three different commands that illustrate this point.

Example P-1. Several commands with different prompts

% ls -lo /var/log % sudo ifconfig lo0 127.0.0.2 netmask 255.255.255.255 # shutdown -r now

The ls command runs as a normal user. The ifconfig command runs as root, but only because a normal user uses sudo to elevate his privileges momentarily (sudo is discussed in detail in Chapter 4). The last command shows the # prompt, assuming that you have already become root somehow before executing the shutdown command.