Linux Essentials

// 1. What is Linux?

Linux is an operating system kernel created by Linus Torvalds in 1991. Unlike Windows or macOS, it is open-source, meaning anyone can view, modify, and distribute the source code.

Linux distributions (distros) combine the Linux kernel with additional software to form complete systems. Popular ones include:

• Ubuntu – user-friendly and widely used for servers and desktops
• Debian – stable and community-driven
• Fedora – cutting-edge and backed by Red Hat
• Arch Linux – minimal and highly customizable
• Kali Linux – specialized for penetration testing and security research

// 2. Linux Architecture

A typical Linux system consists of the following layers:

1. Hardware – The physical components (CPU, memory, storage, etc.)
2. Kernel – The core that interacts with hardware and manages system resources
3. Shell – The command-line interface that interprets user commands
4. Utilities & Applications – Software that helps perform specific tasks

// 3. The Linux File System

Linux follows a hierarchical file system structure. Everything starts from the root (/) directory.

Common directories include:

You can explore them using the command:

ls /

// 4. Essential Linux Commands

Here are some of the most frequently used commands:

Example:

sudo apt update && sudo apt upgrade

This updates and upgrades all packages on a Debian-based system.

// 5. File Permissions

Every file and directory in Linux has three types of permissions:

• r – read
• w – write
• x – execute

These apply to:

• User (u)
• Group (g)
• Others (o)

Example:

chmod 755 script.sh

This gives full permission to the owner, and read/execute to others.

// 6. Package Management

Different Linux distributions use different package managers:

// 7. Shell Scripting Basics

Shell scripts automate repetitive tasks. Example script:

#!/bin/bash
echo "Hello, $(whoami)! Welcome to Linux."

Save it as hello.sh, then run:

chmod +x hello.sh
./hello.sh

// 8. System Monitoring

You can monitor processes and performance using:

• top – real-time process viewer
• htop – interactive process viewer
• df -h – check disk usage
• free -m – check memory usage
• uptime – system load and uptime

// 9. Networking Commands

// 10. Why Learn Linux?

• Runs 90% of cloud infrastructure
• Foundation for cybersecurity, DevOps, and servers
• Helps you understand how computers truly work

// Final Thoughts

Learning Linux is like unlocking the backstage of modern computing. Once you get comfortable with the command line, you gain control, efficiency, and a deeper understanding of how systems work.

Start small — explore, experiment, and break things (in a virtual machine, of course). That’s the true spirit of Linux.