One source of documentation that is generally available on the local system is system manual pages or man pages. Software packages ship these pages to provide documentation, and you can access them from the command line by using the man command. The pages are stored in subdirectories of the /usr/share/man directory.

Man pages originated from the historical Linux Programmer's Manual, which because of its size is split into multiple sections. Each section contains information about a particular topic.

To distinguish identical topic names in different sections, man page references include the section number in parentheses after the topic. For example, passwd(1) describes the command to change passwords, whereas passwd(5) explains the /etc/passwd file format for storing local user accounts.

To read specific man pages, use the man topic command. The man pages display contents one screen at a time. The man command searches manual sections in alphanumeric order. For example, man passwd displays passwd(1) by default. To display the man page topic from a specific section, you can use the man section topic command. For example, man 5 passwd displays passwd(5).

Popular system administration topics are in sections 1 (user commands), 5 (file formats), and 8 (administrative commands). Administrators who use certain troubleshooting tools also use section 2 (system calls). The remaining sections are generally for programmer reference or advanced administration.

It is a critical administration skill to search efficiently for topics and to navigate man pages. Although you can use GUI tools to configure common system resources, using the command-line interface is more efficient. To navigate the command line effectively, you must be able to find the information that you need in the man pages.

The following table lists some navigation commands when viewing man pages:

Use the man command -k option (equivalent to the apropos command) to search for a keyword in man page titles and descriptions. As a result, the keyword search displays a list of keyword-matching man page topics with section numbers. For example, the following command searches for man pages with the word passwd:

[user@host ~]$ man -k passwd
chgpasswd (8)        - update group passwords in batch mode
chpasswd (8)         - update passwords in batch mode
fgetpwent_r (3)      - get passwd file entry reentrantly
getpwent_r (3)       - get passwd file entry reentrantly
...
passwd (1)           - update user's authentication tokens
passwd (1ossl)       - OpenSSL application commands
passwd (5)           - password file
passwd2des (3)       - RFS password encryption
...

The man command -K (uppercase) option searches for the keyword in the full-text page, not only in the titles and descriptions. A full-text search uses greater system resources and takes more time.

With the full-text page search, the man command displays the first page with a match. Press Q to exit this first page, and the man command displays the next page.

In this example, man displays each match, and you can view or skip each one.

[user@host ~]# man -K passwd
--Man-- next: cut(1p) [ view (return) | skip (Ctrl-D) | quit (Ctrl-C) ]
Ctrl-D
--Man-- next: logname(1p) [ view (return) | skip (Ctrl-D) | quit (Ctrl-C) ]
Ctrl-D
--Man-- next: sort(1p) [ view (return) | skip (Ctrl-D) | quit (Ctrl-C) ]
Ctrl-D
--Man-- next: xargs(1) [ view (return) | skip (Ctrl-D) | quit (Ctrl-C) ]
Ctrl-D
--Man-- next: chage(1) [ view (return) | skip (Ctrl-D) | quit (Ctrl-C) ]
Ctrl-C