What does the "tcpdump" command do?

Using cat command, which option is used to print the line number?

How to find out memory usage:

To verify what state (run level) you are currently running in, you use:

You use samba to:

What is pNFS means?

What does permission 777 denote?

What is the purpose of the makewhatis command?

Linux operating system is:

What is the purpose of the touch command?

The user's current path is /root/Desktop/abc. If he runs $ cd ../../../ what will be the user's current working directory?