Find commands in your system

1.find first command in your path
#type ls

2.find command anywhere is your system
#locate ls
#/usr/libexec/locate.updatedb
update locate database

3.find standand library, man pages and source to fine command
#whereis ls

4.search path environment varible to fine command
#which ls

5.find commands from packages
#pkg_info -W openvpn

6.want to find man pages with certain keyword
#apropos passwd

7.search whatis database
#whatis passwd