Linux man pages cheat sheet

The chapter on one page: what to remember, the commands to have at your fingertips, and flashcards for quick revision.

The chapter in six sentences

man NAME opens a manual page in less: search with /, move with Space and b, quit with q.
The manual has numbered sections: 1 for user commands, 5 for file formats, 8 for administration commands. man 5 passwd picks the section; whatis lists which exist.
A SYNOPSIS shows what to type: square brackets are optional, ... may repeat, capitals are placeholders, and {a|b} means choose one.
man -k WORDS (apropos) finds pages by keyword in their names and descriptions; man -K searches full text; mandb maintains the index.
COMMAND --help gives a quick option summary; type tells built-ins, aliases and programs apart, and help documents built-ins.
Packages leave READMEs and examples in /usr/share/doc, and the full RHEL documentation is online at docs.redhat.com.

Command	Does
`man NAME`, `man N NAME`	Open a manual page; from section N
`whatis NAME` (`man -f`)	One-line descriptions of every page called NAME
`man -k WORDS` (`apropos`)	Search names and descriptions
`man -k -s 8 WORDS`	Only section 8
`man -K WORD`	Search the full text of every page (slow)
`man -w NAME`	Where the page's file is
`mandb`	Rebuild the keyword index (as root)
`COMMAND --help`	Quick option summary
`type NAME`, `type -a NAME`	Built-in, alias or program; every match
`help BUILTIN`	Help for a shell built-in
`ls /usr/share/doc/PACKAGE`	Package documentation

In a manual page	Does
Space / `b`, `d` / `u`	Page down / up, half page down / up
`/text`, `n`, `N`	Search, next match, previous match
`g` / `G`	Start / end
`q`	Quit

Which manual sections does an administrator use most, and for what?: **1** user commands, **5** file formats, **8** administration commands.
Open the manual page for the /etc/passwd file format?: `man 5 passwd`
In a SYNOPSIS, what do [ ], ... and CAPITALS mean?: Optional, may repeat, and a placeholder to replace with your own value.
Search manual pages by keyword?: `man -k WORDS` or `apropos WORDS`
What builds the index that man -k searches?: `mandb`, run as root (RHEL runs it when packages install).
How do you tell whether a command is a built-in?: `type NAME`. Then `help NAME` documents a built-in.
Where do packages keep READMEs and examples?: `/usr/share/doc/PACKAGE`
Search inside a manual page, and find the next match?: `/text` then Enter; `n` for the next match, `N` for the previous.