Find it online Linux Fundamentals

Linux Fundamentals

High Level Goals

By the end of this lesson, you will be familiar with the following:

1. A Bit of Background on Kali Linux
2. What is Terminal and running our first few commands
3. File System commands
4. Searching for Files
5. starting with Shell Operators

A Bit of Background on Kali Linux

Kali Linux is an open-source project that aims to provide advanced Penetration Testing and security auditing tools. It contains hundreds of tools that are designed to address various security tasks, such as Computer Forensics and Security Research.

What is Terminal and running our first few commands

The "Terminal" it is a text-based interface that allows you to enter commands, execute them, and view the results.

→ This is what a terminal looks like
┌──(tetra㉿kali)-[~]
└─$ enter commands here

Let's get started with two of the first commands, which I have broken down in the table below:

Command	Description
echo	Output any text that we provide
whoami	Find out what user we're currently logged in as!

→ Using echo
┌──(tetra㉿kali)-[~]
└─$ echo Hello World
 Hello World

→ using whoami
┌──(tetra㉿kali)-[~]
└─$ whoami
 tetra

File System commands

Command	Full Name
ls	listing
cd	change directory
cat	concatenate
pwd	print working directory

Listing Files in Our Current Directory (ls)

This ls command will help us identify the contents of all files and folders in our system.

→ Using "ls" to to list the contents of the current directory
┌──(tetra㉿kali)-[~]
└─$ ls
'Download' 'My Documents' 'Notes' 'Pictures'

Pro tip: You can list the contents of a directory without having to navigate to it by using ls and the name of the directory. I.e. ls Pictures

Changing Our Current Directory (cd)

we need to use the cd command (short for change directory) to change to that directory.

 → using cd
┌──(tetra㉿kali)-[~]
└─$ cd Pictures

┌──(tetra㉿kali)-[~/Pictures]
└─$ ls
dog_picture1.jpg cat_picture1.jpg dog_picture2.jpg cat_picture2.jpg

Outputting the Contents of a File (cat)

In this tutorial, we'll talk about a command called cat, which will output the contents of text files. ┌──(tetra㉿kali)-[/Documents] └─$ ls todo.txt → Using cat ┌──(tetra㉿kali)-[/Documents] └─$ cat todo.txt This is the what cat showing for us!

We've applied some knowledge from earlier in this section to do the following:

1. Used ls to let us know what files are available in the "Documents" folder of this machine. In this case, it is called "todo.txt".
2. We have then used cat todo.txt to concatenate/output the contents of this "todo.txt" file, where the contents are "Here's something important for me to do later

Pro tip: You can also output the contents of a file without having to navigate it by using cat.. cat /home/Kali/Documents/todo.txt

Finding out the full Path to our Current Working Directory (pwd)

It's easy to lose track of where we are on the file system exactly, which is why I want to introduce pwd. This stands for print working directory.

┌──(tetra㉿kali)-[~/Documents]
└─$ pwd
/home/tetra/Documents

Searching for Files

One fantastic way to show just how efficient you can be with systems like this is using a set of commands to quickly search for files across the entire system that our user has access to. No need to consistently use cd and ls to find out what is where. we can will use command find.

Using Find

Take the snippet below, we can see a list of directories available to us:

┌──(tetra㉿kali)-[~]
└─$ ls
Desktop Documents Pictuers folder1

┌──(tetra㉿kali)-[~]
└─$ find -name passwords.txt
./folder1/passwords.txt

"Find" has managed to find the file — it turns out it is located in folder1/passwords.txt.

We can use what's known as a wildcard (*) to search for anything that has .txt at the end.

┌──(tetra㉿kali)-[~]
└─$ find -name *.txt
./folder1/passwords.txt
./Documents/todo.txt

Find has managed to find:

1. "passwords.txt" located within "folder1"
2. "todo.txt" located within "Documents"

starting with Shell Operators

Shell-operator is a tool for running event-driven scripts in a Kubernetes cluster.

Symbol / Operator	Description	How we use it
&	This operator allows you to run commands in the background of your terminal.	The "&" shell operator allows us to execute a command and have it run in the background (such as this file copy) allowing us to do other things!
&&	This operator allows you to combine multiple commands together in one line of your terminal.	for example command1 && command2. However, it's worth noting that command2 will only run if command1 was successful.
>	This operator is a redirector - meaning that we can take the output from a command (such as using cat to output a file) and direct it elsewhere.	Let's say we wanted to create a file named "welcome" with the message "hello world". We can run echo hello world > welcome where we want the file created with the contents "hello world"
>>	This operator does the same function of the > operator but appends the output rather than replacing (meaning nothing is overwritten).	The >> operator allows to append the output to the bottom of the file — rather than replacing the contents echo hello >> welcome

Practice

You Can answer these Question in this form [add Google form]

1. What year was the first release of a Linux operating system?

2. If we wanted to output the text "MerakiAcademy", what would our command be?

3. If we wanted to run a command in the background, what operator would we want to use?

4. If I wanted to replace the contents of a file named "passwords" with the word "password123", what would my command be?

5. Now if I wanted to add "MerakiAcademy" to this file named "passwords" but also keep "passwords123", what would my command be.