man pages

Overview

Linux is self-documenting through manual pages (man pages) — built-in reference documentation for commands, configuration files, and system calls. Learning to read them makes you self-sufficient, which is a defining trait of a capable Linux user. This lesson covers using the manual system.

Learning objectives

• Use the man command to read documentation.
• Understand the structure of a man page and its sections.
• Find help when a man page is not enough.

Core concept

The man command displays the manual page for a topic: man ls shows documentation for ls. Man pages are organized into numbered sections, notably:

• 1 — user commands (e.g. ls, cp).
• 5 — file formats and configuration files (e.g. man 5 passwd for the /etc/passwd format).
• 8 — system administration commands.

A single page has consistent parts: NAME, SYNOPSIS (usage syntax), DESCRIPTION, OPTIONS, EXAMPLES, and SEE ALSO.

How it works

Run man <topic> to open the page in a pager (scroll with arrows/space, quit with q, search with /pattern). The SYNOPSIS shows the command's syntax, with optional parts in [brackets]. When the same name exists in multiple sections, specify the section number (e.g. man 5 crontab vs man 1 crontab). Beyond man, many commands support --help for a quick summary, and apropos <keyword> searches man page descriptions to find relevant commands.

Practical example

Unsure how to make ls show hidden files, you run man ls, search with /all, and find the -a, --all option documented. For the format of a config file rather than a command, man 5 fstab explains the /etc/fstab file's fields. A quick ls --help would also list options rapidly without opening the full manual.

Cybersecurity relevance

Self-sufficiency with documentation is vital in security work, where you constantly encounter unfamiliar commands and configuration files, often on systems without internet access. Man pages let you verify exact syntax and options before running powerful commands, reducing mistakes. Section 5 pages are especially useful for understanding configuration file formats you may need to inspect during hardening or investigation.

Common mistakes

• Guessing options instead of checking man/--help, risking errors with powerful commands.
• Ignoring section numbers, missing that a name may have both a command (1) and a file-format (5) page.
• Forgetting apropos/man -k to discover commands by keyword.

Key takeaways

• man <topic> opens built-in documentation; navigate with the pager (space/arrows, / to search, q to quit).
• Man pages have numbered sections (1 commands, 5 file formats, 8 admin) and a consistent structure (NAME, SYNOPSIS, DESCRIPTION, OPTIONS, EXAMPLES).
• Use --help for quick summaries and apropos/man -k to find commands by keyword — self-sufficiency is essential in security work.

Check your understanding

• How would you read the documentation for the file format of a config file rather than a command of the same name?
• What does the SYNOPSIS section of a man page show, and what do square brackets indicate there?