In Linux the man command displays the help(man page) for a command. man fdisk is "display the man page for command fdisk"
The whoami command.
Displays the detailed status of a particular file or a file system. You can always refer manual pages for linux commands using the terminal using the "man" keyword before the actual command. ex:- man stat
The history command displays all commands that have been entered into the terminal.
Exactly what the name says: It displays and sets the date on a Linux system.
The command pwd displays your current/present working directory.
iptable in Linux
"man" is part of Linux. You could try "info" if you really wanted.
In Linux, command typed at a command prompt displays a list of commands that would likely contain the command you desire. For example, to find all of the commands that have word flush in their name or descriptions type the following: man -k flush
The time command is used to time a command and not display the actual time. To display the time and date, the date command must be used.
The chmod command. For it's usage, consult it's manual page with the... $ man chmod command....
The df command displays drive capacities. The free command will show memory usage. The top command will show the system load of various processes.