Linux Man-Pages

Linux is great, but at times you can become a bit frustrated. Especially if you cant remember what you are doing at the command line or you don’t work with it that often.

For example:

You find yourself sitting at the command prompt and you want to make some changes to your Apache web server, but you have not done the task very often or it’s just been a while and as you’re getting a bit older, your mobile phone likely has greater memory than you.

You reach for the favorite search engine … WAIT.

All you should need is 1 command. After all this is Linux.

# man man

MAN(1) Manual pager utils MAN(1)

NAME
man – an interface to the on-line reference manuals

*** Snipped

For example, suppose I know I want to do something with Apache, you can search using keywords with the -k switch:

# man -k apache

a2dismod (8) – enable or disable an apache2 module
a2dissite (8) – enable or disable an apache2 site / virtual host
a2enmod (8) – enable or disable an apache2 module
a2ensite (8) – enable or disable an apache2 site / virtual host
ab (1) – Apache HTTP server benchmarking tool
apache2 (8) – Apache Hypertext Transfer Protocol Server
apache2ctl (8) – Apache HTTP server control interface
apachectl (8) – Apache HTTP server control interface
check_forensic (8) – tool to extract mod_log_forensic output from apache log files
DBI::ProfileDumper::Apache (3pm) – capture DBI profiling data from Apache/mod_perl
logresolve (1) – Resolve IP-addresses to hostnames in Apache log files
rotatelogs (8) – Piped logging program to rotate Apache logs

Ok, we can see the list of commands related to Apache. We can read the desciption and maybe that is enough of a reminder. But what do the numbers mean?

Ask man:

# man man-pages

**Snipped

Sections of the Manual Pages
The manual Sections are traditionally defined as follows:

1 Commands (Programs)
Those commands that can be executed by the user from within a shell.

2 System calls
Those functions which must be performed by the kernel.

3 Library calls
Most of the libc functions.

4 Special files (devices)
Files found in /dev.

5 File formats and conventions
The format for /etc/passwd and other human-readable files.

6 Games

7 Conventions and miscellaneous
Overviews of various topics, conventions and protocols, character set standards, and miscellaneous other things.

8 System management commands
Commands like mount(8), many of which only root can execute.

 

Turns out the numbers are sections of the man-pages. So this information might help you further to decide if the one you suspect is actually the command you are looking for. Great

Then you can dig deeper into the command, reading all of the useful information or just paying attention to the specific areas of interest:

# man a2dismod

***Snipped

DESCRIPTION
This manual page documents briefly the a2enmod and a2dismod commands.

a2enmod is a script that enables the specified module within the apache2 configuration. It does this by creating symlinks within /etc/apache2/mods-enabled. Likewise, a2dismod disables a module by
removing those symlinks. It is not an error to enable a module which is already enabled, or to disable one which is already disabled.

Note that many modules have, in addition to a .load file, an associated .conf file. Enabling the module puts the configuration directives in the .conf file as directives into the main server con‐
text of apache2

EXAMPLES
a2enmod imagemap
a2dismod mime_magic

Enables the mod_imagemap module, and disables the mod_mime_magic module.