Documentation and Help

Linux is a powerful and flexible operating system that is widely used in a variety of settings, from personal computers to servers and supercomputers. One of the strengths of Linux is the wealth of documentation and help available to users. Below are several options to get documentation or help about commands and the system in general:

man pages

Short for manual pages, the man program is in charge of searching and showing documentation.

• A given topic may have multiple pages associated with it and there is a default order determining which one is displayed when no options or section number is specified (in /etc/man_db.conf)
• The man pages are divided into chapters numbered 1 through 9

man command #Shows the manual entry for the command
man -f command #Lists all entries (can be more than one) for the command
whatis command #Same as above
man -k command #List all entries where the command is mentioned (can be from other commands)
apropos command #Same as above
man -a command #display all "command" pages in all chapters, one after the other

TLDR

As an alternative for the man pages, the the tldr-pages project provides summarized documentation for commands, with a focus on practical examples. It does not come installed by default, but after installing it, here is an example when running tldr tldr :

foo@bar:~$ tldr tldr
tldr
Display simple help pages for command-line tools from the tldr-pages project.More information: https://tldr.sh.

 - Print the tldr page for a specific command (hint: this is how you got here!):
   tldr {{command}}

 - Print the tldr page for a specific subcommand:
   tldr {{command}}-{{subcommand}}

 - Print the tldr page for a command for a specific [p]latform:
   tldr -p {{android|linux|osx|sunos|windows}} {{command}}

 - [u]pdate the local cache of tldr pages:
   tldr -u

GNU Info

• Similar to man but works with subsections and links
• Accessible through info tool.

To navigate:

--help and help

• --help :Most commands provide a short way to get some reference passing the --help flag.
• help Is a program that can be used inside bash shells to get help about commands that run especially built-in bash versions. A list of these commands is shown using help

Other sources

Include:

• Desktop help system: All Linux desktop systems have a graphical help application. This contains desktop specific help as well as some rendered man and info pages. Can be ran from GUI or CLI (For example, for GNOME gnome-help or yelp)
• Package documentation: Linux documentation is also available as part of the package management system. Usually, this documentation is directly pulled from the upstream source code, but it can also contain information about how the distribution packaged and set up the software. Normally available in /usr/share/doc
• Online resources: Include forums, and doc pages. Also ebooks, like this one