Aakansh Nahadiya's Space

What Is an Operating System?

An operating system is a set of programs that works between the user and the computer hardware. It helps the system manage memory, the processor, files, and connected devices.

Without an operating system, the hardware alone cannot do anything useful. The OS makes sure that both the system and the user can work properly by keeping files organized and by allowing programs to run smoothly.

Introduction to Linux

Linux is a UNIX-like operating system. It was released in 1991 by Linus Torvalds, who was a student at the University of Helsinki at that time. Today, Linux is used on many kinds of devices, such as personal computers, servers, smartphones, and other systems.

Some important things that make Linux different are:

• It is open-source, which means its source code is publicly available and anyone can study, modify, or distribute it.
• It is multi-user and multitasking, so more than one user can use the system, and many programs can run at the same time.
• Although Linux is not exactly the same as UNIX, it follows many of the same ideas and principles.

Linux is available in many versions, which are called distributions or distros. Different distributions are made for different needs.

Some common Linux distributions are:

• Ubuntu - One of the most beginner-friendly Linux distributions. If you are starting for the first time, Ubuntu is a good place to begin. This guide also continues from my Ubuntu installation post.
• Linux Mint - A good option for people who are moving from Windows, because it feels more familiar.
• Debian - Known for stability and reliability. Ubuntu is also based on Debian.
• RHEL (Red Hat Enterprise Linux) - Commonly used in enterprise environments and professional servers.
• CentOS - Was widely used in the Red Hat ecosystem and was common on many servers.

Architecture of Linux

To understand Linux better, it helps to know that it works in different parts, and each part has its own job.

The first part is the hardware. This means the physical parts of the computer, such as the processor, RAM, storage, keyboard, and other devices.
You can think of hardware as the actual body of the computer.

Above the hardware is the kernel. The kernel is the core part of Linux. It directly talks to the hardware and manages important things like memory, processes, and system resources. You do not normally interact with the kernel directly, but it is always working in the background.
In a simple way, the kernel is like the brain that controls the body.

Then comes the shell. The shell works like a bridge between you and the system. When you type a command in the terminal, the shell reads it, understands it, and passes it to the kernel so the system can do the required task.
You can think of the shell as a messenger between you and the computer.

Above that are the user applications. These are the programs you actually use, such as a browser, media player, file manager, text editor, or terminal itself. In simple words, these are the tools through which users do their daily work.
These are like the things you use in daily life to get your work done.

Linux also includes many utilities and tools that help with common tasks such as managing files, installing software, checking system information, and configuring the system.
These are like extra helper tools that make work easier.

Linux Directory Structure

In Windows, we usually see different drives like C:\ and D:\. Linux works in a different way. It has one main directory, which is called the root directory and is written as /. Everything in Linux starts from this root. Even external drives and other storage devices are attached somewhere inside this same structure.

This may feel a little different in the beginning, but once you understand it, Linux becomes much easier to use.

Linux Terminal Commands

This is one of the most important parts of Linux. The terminal is a place where you can give commands directly to the system. Although Linux also provides graphical tools, the terminal is often faster, more powerful, and more useful for many tasks.

In the beginning, the terminal may look difficult or confusing, especially if you are coming from Windows. But once you start using a few basic commands, it becomes much easier to understand.

One good thing about the terminal is that it works almost everywhere. Whether you are using a normal desktop system or a server without any graphical interface, commands still work.

In simple words, the terminal is one of the most direct ways to control Linux.

In the next sections, I will explain some useful Linux commands and what they do.

Navigation

Before doing anything in Linux, it is important to know how to move from one directory to another and how to check where you currently are. These are some of the basic navigation commands that you will use again and again.

Note:
Linux uses the $ symbol before commands. For example, $ cd. In most cases, you do not need to enter the $ symbol because Linux usually shows it automatically. This is just for reference. If a command does not work, or Linux does not add this symbol by itself, then you can add $ before each command.
Now start with actual commands:

pwd

This command shows your current location in the file system. pwd stands for Print Working Directory.

pwd --help

This shows help and available options for the pwd command. In Linux, many commands support the --help option.

cd ~

This command takes you to your home directory from wherever you are.

cd ..

This moves you one level back, which means it takes you to the parent directory.

cd /

This takes you directly to the root directory, which is the main starting point of the Linux file system.

cd /path/to/folder

This is used when you want to go to a specific folder by writing its full path. For example:

cd /home/aakansh/Documents

ls

This command lists the files and folders in the current directory.

ls -l

This also lists files and folders, but in a detailed form. It shows information such as file permissions, owner, size, and modification date.

These commands may look simple, but they are very important. Once you become comfortable with them, using the Linux terminal becomes much easier.

File and Directory Management

After learning how to move around in Linux, the next step is to understand how to create, remove, copy, and move files or directories. These commands are part of daily Linux use.

touch filename.txt

This creates a new empty file. If the file already exists, it updates its timestamp.

mkdir foldername

This command creates a new directory.

mkdir "Folder With Spaces"

If the folder name contains spaces, you should write it inside quotes.

mkdir folder1 folder2

This creates multiple directories at the same time.

rmdir foldername

This removes a directory, but it only works if that directory is empty.

rmdir folder1 folder2

This removes multiple directories, but both must be empty.

rm filename.txt

This permanently deletes a file. There is no Recycle Bin in the terminal, so once deleted, it is gone.

cp file1.txt file2.txt

This creates a copy of one file with a new name.

cp -r folder1 folder2

This copies an entire directory and everything inside it. The -r option means recursive.

cp /path/to/file /destination/

This copies a file from one location to another.

mv file.txt /path/to/destination/

This moves a file to another location.

mv oldname.txt newname.txt

This renames a file. In Linux, mv is used both for moving and renaming.

Viewing File Content

Sometimes you do not want to edit a file. You just want to quickly see what is inside it. These commands help with that.

cat filename.txt

This displays the full content of a file directly in the terminal.

less filename.txt

This opens the file in a scrollable view. It is more useful when the file is large. Press q to quit.

file filename.txt

This tells you the type of a file and gives some basic information about it.

Writing to Files

Linux also lets you write text directly from the terminal. These commands are simple, but you should use them carefully.

echo "Some text"

This prints whatever you write to the terminal screen.

echo "Some text" > filename.txt

This writes the text into a file. If the file already contains something, the old content will be replaced.

echo "More text" >> filename.txt

This adds text to the file without removing the content that is already there. One > replaces, while two >> append.

System and User Information

These commands help you know more about the current user, time, command history, and some small everyday tasks.

whoami

This shows the username of the currently logged-in user.

date

This shows the current system date, time, timezone, and day.

date +%T

This shows only the current time.

cal

This displays the calendar for the current month.

cal 04 2026

This shows the calendar for a specific month and year.

In case the cal command does not work, then run: sudo apt install ncal

history

This shows previously run commands from your shell history.

expr 10 + 5

This evaluates a simple mathematical expression. For example, the output here will be 15.

command1 ; command2

This allows you to run two commands in the same line, one after the other.

Admin and Software Management

Some tasks in Linux need administrator access, especially when you are updating the system or installing software. These commands are commonly used for that purpose.

sudo

This stands for Super User Do. It gives administrator-level permission for a single command. Linux usually asks for your password when you use it.

Example:

sudo apt update

This updates the package manager with the latest list of available software. It is usually a good idea to run this before installing anything.

sudo apt install packagename

This installs a package. You have to replace packagename with the actual name of the software.

For example:

sudo apt install vlc

apt list

This shows a list of available packages.

exit

This ends the current terminal session.

logout

This logs out the current user in some shell sessions.

Getting Help

No one remembers every command and every option from the beginning. Linux provides built-in help commands, and they are very useful while learning.

whatis ls

This gives a one-line description of a command.

ls --help

This shows available options and parameters for the command.

info ls

This opens detailed documentation about the command inside the terminal. It is often more detailed than --help.

In the end:

The terminal takes some getting used to, but these commands cover many of the things you will need at the beginning. The best way to understand them is not only by reading, but also by trying them on a real Linux system.

Once you become comfortable with basic navigation, file handling, and software management, Linux starts feeling much less difficult.

Also, the world of Linux commands does not end here. There are a lot of commands that we might discuss later, whenever I learn them.

Thank you for reading,
Have a great Linux journey.