Linux Commands are CaSe SeNsItIvE
The first thing to know is that Linux commands are CaSe SeNsItIvE - meaning that if you type the commands in the wrong case (uppercase or lowercase or mixed-case), the command will not work and you will most likely get a “command not found” message on the terminal.

Type in date and press enter.
You should see the date and timestamp displayed on your terminal screen.

Now type in Date (with an uppercase Date) and press enter.
You will be notified that there is no command called Date and that the Date command is not found.
You may also be suggested other commands that Linux would recognize as shown below.
No command 'Date' found, did you mean: Command 'date' from package 'coreutils' (main) Command 'yate' from package 'yate' (universe) Command 'late' from package 'late' (universe) Command 'kate' from package 'kate' (universe) Date: command not found

This proves that Linux is CaSe SeNsItIvE!

A Linux Commands cheatsheet has been created for you. You can access it at CyberShaolin Linux Commands Cheatsheet. We recommend that you print this out and use it as a reference when doing the training exercises and the CyberShaolin hackercises.