Kali Linux

 Linux Tutorial

Last Updated : 11 Dec, 2025

Linux is one of the most widely used open-source operating systems. It's fast, secure, stable, and powers everything from smartphones and servers to cloud platforms and IoT devices. Linux is especially popular among developers, system administrators, and DevOps professionals.

• A Unix-like OS used in servers, cloud infrastructure, supercomputers, personal computers, and embedded systems.
• Reliable and secure, making it ideal for web hosting, networking, and automation.
• Preferred in DevOps, where it's used for scripting, configuration, containerization (Docker), and CI/CD pipelines.
• Open-source and customizable, giving users full control over their systems and workflows.
  

  Understanding Linux Basics

  This section introduces what Linux is, how it works, and foundational concepts.
  

  Introduction to Linux Operating System

  Last Updated : 05 Dec, 2025

  Linux is based on the UNIX operating system. UNIX is a powerful, multi-user, multitasking operating system originally developed in the 1970s at AT&T Bell Labs. It laid the foundation for many modern operating systems, including Linux.

  • Linux is free and open-source, accessible to everyone.
  • This promotes global collaboration and innovation.
  • Linux offers efficient performance and strong security.
  • It works well across many devices and industries.

  Linux combines a wide range of open-source tools and components to form a complete computing environment. These components include file systems, user interfaces, system utilities, and application programs all working together to manage hardware and enable users to interact with their computer systems.

  Distributions in Linux

  A Linux distribution is a complete operating system built around the Linux kernel, combined with system software, libraries, and applications. It provides users with everything needed to run Linux on different types of devices.

  • A distribution includes the Linux kernel, system libraries, and essential software tools.
  • Different distributions are designed for different purposes such as desktops, servers, and embedded systems.
  • Each distro comes with its own package manager, desktop environment, and default applications.
  • Users can choose distributions based on performance, stability, ease of use, or customization level.

  Popular Linux Distributions

  Around 600 + Linux Distributions are available and some of the popular Linux distributions are: 

  • MX Linux
  • Manjaro
  • Linux Mint
  • elementary
  • Ubuntu
  • Debian
  • Solus
  • Fedora
  • openSUSE
  • Deepin

  Importance of Linux

  Linux is a free, open-source operating system known for its flexibility, stability, and strong security. It is widely used in personal computing, server environments, and enterprise systems because of its performance and customization capabilities.

  • Offers high security and stability, making it ideal for servers and development work.
  • Fully open-source and free to use, modify, and distribute.
  • Highly flexible and customizable to suit different user and industry needs.
  • Supported by a large global community and a vast software ecosystem.

  Architecture of Linux

  Linux architecture refers to the layered structure of the Linux operating system that defines how its components - such as the kernel, shell, system libraries, and hardware - interact with each other to manage system resources and execute user programs efficiently. It has the following components: 

  

  1. Kernel

  The Kernal is the core of the Linux operating system that manages hardware resources and controls communication between software and hardware.

  • Handles process management, memory, and device control.
  • Prevents conflicts between multiple running programs.

  Types of Kernels: Monolithic, Microkernel, Hybrid, Exokernel

  2. System Libraries

  System libraries provide essential functions that allow applications to interact with the kernel without needing to access it directly.

  • Contain reusable pre-written code for common system operations.
  • Act as an interface between applications and the Linux kernel.

  3. Shell

  The Shell is the command-line interface that allows users to communicate with the operating system by entering commands.

  • Interprets and executes user commands.
  • Acts as a bridge between user actions and kernel processing.

  4. Hardware Layer

  The hardware layer consists of physical components that execute commands and provide system resources.

  • Includes CPU, RAM, storage, and input/output devices.
  • Communicates with the OS using device drivers and kernel services.

  5. System Utilities

  System utilities are built-in tools that help users manage, configure, and maintain the operating system.

  • Used for tasks like software installation, user management, and monitoring.
  • Simplify system administration processes for both beginners and administrators.

  Applications of Linux Operating System

  The Linux operating system is widely used across multiple domains due to its flexibility, strong security, and open-source nature. It supports a wide range of applications across different industries, as outlined below.

  

  [Application 1]: Servers and Hosting

  • Powers most web servers, cloud platforms, and data centers worldwide.
  • Offers high stability, security, and uptime for critical services.

  [Application 2]: Development

  • Provides powerful tools and environments for coding, testing, and debugging.
  • Supports multiple programming languages and frameworks.

  [Application 3]: Desktop and Personal Use

  • Offers customizable and secure desktop environments.
  • Supports daily computing tasks like browsing, office work, and media usage.

  [Application 4]: Cybersecurity

  • Widely used for ethical hacking and penetration testing (e.g., Kali Linux).
  • Provides advanced tools for threat detection and security analysis.

  [Application 5]: Embedded Systems

  • Runs efficiently on low-resource devices like IoT and routers.
  • Supports real-time processing and hardware-level control.

  [Application 6]: Supercomputers

  • Used in high-performance computing environments worldwide.
  • Handles massive scientific calculations and simulations efficiently.

  [Application 7]: Education

  • Helps students learn programming, networking, and system administration.
  • Free and open-source, making it ideal for academic institutions.

  Selecting a Linux Distribution Based on Your Requirements

  Selecting a Linux distribution depends on your personal needs, experience level, and the purpose for which you want to use the operating system. Different distributions are designed for tasks like development, security, servers, or everyday desktop use, offering flexibility and customization for every type of user.

  For Beginners

  • Ubuntu provides an easy-to-use interface with strong community support for new users.
  • Linux Mint offers a Windows-like experience, making it comfortable for first-time Linux users.

  For Advanced Users

  • Arch Linux is known for minimalism and deep system customization.
  • Gentoo allows full control over system configuration but requires advanced knowledge.

  For Developers

  • Fedora offers the latest development tools and technologies.
  • Debian is highly stable with a large software repository for development and production.

  For Servers

  • CentOS provides enterprise-level stability similar to Red Hat Enterprise Linux (RHEL).
  • Ubuntu Server is popular for its ease of use and strong community support.

  For Lightweight Systems

  • Lubuntu is optimized for low-resource systems and older hardware.
  • Puppy Linux is extremely lightweight and runs well on very old computers.

  For Security Professionals

  • Kali Linux is designed for penetration testing and ethical hacking with pre-installed security tools.
  • Used widely for cybersecurity training, vulnerability assessment, and digital forensics.

  Installing Linux

  Selecting a Ubuntu, Fedora, or Linux Mint distribution which suits your needs is the initial step in the straightforward procedure for installing Linux.

  

  Installing Linux on bootable USB drive

  • Download the ISO file from the official Linux distribution website.
  • Create a bootable USB using Rufus (Windows) or Balena Etcher (Linux/macOS).
  • Insert the USB drive and restart your computer.
  • Enter BIOS/UEFI settings and set the USB as the first boot device.
  • Boot from the USB and start the Linux installation process.
  • Select language, partition disk, and create a user account.
  • Complete the installation, remove the USB, and reboot the system.

  Installing Software on Linux

  On Linux, installing software is simple.

  • For Debian-based systems (like Ubuntu), use package managers like apt

  sudo apt install package_name

  • For Fedora, use dnf

  sudo dnf install package_name

  • Software centers are another source for a graphical application installation and searching interface.
  • For Python installation specifics, detailed guidance can be found in the provided link.

  Linux Commands

  Basic tools for utilizing the command line interface (CLI) to communicate with the operating system are Linux commands. Commonly used commands like:

  • ls – Lists contents of directories
  • cd – Changes the current directory
  • pwd – Displays the current directory path
  • cp, mv, rm – Used to copy, move, and delete files respectively
  • free – Shows memory usage
  • df – Checks disk space usage
  • top – Monitors running processes
  • netstat, ifconfig, ping – Help monitor and troubleshoot network connections

  Package management differs depending on the distribution; Fedora-based machines use dnf, while Debian-based systems use apt. Commands like cat, grep, awk, and sed are required for editing text files. Knowing and performing these directions well enables. For clear understanding about the Linux commands refer this link.

  History of Linux

  The history of Linux shows its growth from a personal project into the backbone of modern computing systems worldwide.

  [Phase-1]: Creation

  • Linux was created by Linus Torvalds in 1991 as a free and open-source operating system kernel.
  • It was inspired by UNIX and the MINIX operating system.

  [Phase-2]: Community Development

  • Developers from around the world contributed to improving the Linux kernel.
  • This led to the development of complete Linux systems called Linux distributions.

  [Phase-3]: Growth and Adoption

  • Linux started being used in servers, desktops, and enterprise environments.
  • Major distributions like Debian, Red Hat, and Ubuntu increased its popularity.

  [Phase-4]: Modern Linux

  • Today, Linux powers servers, supercomputers, smartphones (Android), cloud systems, and embedded devices.
  • It is valued for its security, stability, and open-source nature.
    
    

    Linux Kernel

    Last Updated : 11 Jul, 2025

    Linux Kernel is the heart of Linux operating systems. It is an open-source (source code that can be used by anyone freely) software that is most popular and widely used in the industry as well as on a personal use basis. Who created Linux and why? Linux was created by Linus Torvalds in 1991 as a hobby project. Since then, many of the users have contributed to its growth and development of it. Before Jumping directly to the main topic "Linux Kernel" one must know a few concepts (prerequisites) to better understand the Linux Kernel.

    What is Linux Operating System and Kernel?

    An operating system (OS) is a software system that manages the computer that provides some services for computer programs and manages computer hardware and software. Basically, it is a communication or resource allocation between computer hardware and applications. It provides some services like managing input and output devices, managing file systems, providing UI (User Interface) and also managing computer memory. It also governs and executes all the programs. 

    Linux operating System also consists of various components for example system libraries, user-space utilities, Linux kernel, and applications. The kernel is the core component of an operating system. This provides a platform for programs and various services to run on top of it. The Linux kernel is modifiable according to the user's needs. Overall, the Linux Operating System and Linux kernel together provide a strong and user-friendly platform.  

    In a General-Purpose Computer running many processes simultaneously, we need a middle layer to manage the distribution of the computer's hardware resources efficiently and fairly among all the various processes running on the computer. This middle layer is referred to as the kernel. The kernel virtualizes the computer's common hardware resources to provide each process with its own virtual resources. This makes the process seem as if it is the sole process running on the machine. The kernel is also responsible for preventing and mitigating conflicts between different processes. This is schematically represented below: 

    

    Schematical representation of Kernel working

    Figure: Virtual Resources for each Process

    The Core Subsystems of the Linux Kernel are as follows:

    1. The Process Scheduler
    2. The Memory Management Unit (MMU)
    3. The Virtual File System (VFS)
    4. The Networking Unit
    5. Inter-Process Communication Unit

    

     Core Subsystems of the Linux Kernel 

    Figure: The Linux Kernel for the purpose of this article we will only be focusing on the 1st three important subsystems of the Linux Kernel. The basic functioning of each of the 1st three subsystems is elaborated below:

    • The Process Scheduler: This kernel subsystem is responsible for fairly distributing the CPU time among all the processes running on the system simultaneously.
    • The Memory Management Unit: This kernel sub-unit is responsible for proper distribution of the memory resources among the various processes running on the system. The MMU does more than just simply provide separate virtual address spaces for each of the processes.
    • The Virtual File System: This subsystem is responsible for providing a unified interface to access stored data across different filesystems and physical storage media.

    Some Basic Commands:

    Some Basic Commands we need to know while working on Linux Kernel. 

    • `ls` : Use to list all the files and directories in a particular location specified by us.

    Syntax: 

    ls [OPTION] [FILE]

    Example:

    In this example we are going to list all the file and directories in our current location , we have one directory name `snap`.

     Here in second time we use `a` option (to see all the hidden files).

     In third time we specified a `snap` directory.

    

    ls command

    • `mkdir` : In this we will create a new directory.

    Syntax:  

    mkdir [OPTION] DIRECTORY

    Example:

    In this we will make a directory name `test` and to check it we can use command `ls`.

    

    mkdir command

    • `cat` : In this we will print the context inside a text file on terminal.

    Syntax: 

    cat [OPTION] [FILE]

    Example: 

    Printing a content inside a text file name `example`.

    

    cat command

    • `pwd` : In this we will get to know the name and path of the current working directory.

    Syntax: 

    pwd

    Example:

    

    pwd command

    Conclusion:

    The most powerful and versatile component of the Linux Operating System is known as the Linux kernel. The Kernel has provided a wide range of features, for example, memory management, filesystem management, process management, device drive management and networking support. After understanding all this one can conclude that customizability and extensibility have made it the most popular choice for a computer system.
    
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    Linux Tutorials | Getting Started | Introduction