apropos:

-Searches for a given keyword in the top line (description) of all man pages then displays all that match

-Useful if you do not know the name of a command but you have a specific task you want to perform

Format

            aproposkeyword

            i.e.

            apropos locate 

Note: man –k keyword

            i.e.

            man –k who

will give the same result as

apropos who

 
Whatis Database

-Database used by apropos is called whatis

-created by a cron job that runs weekly using a utility called makewhatis

-The cron utility runs the /etc/cron.weekly/makewhatis.cron script to build/update the whatis database

-If  the system is turned off periodically (as with a laptop/desktop), the script may not run.
-To keep apropos updated run command, as root run:

  makewhatis -w