🐧Linux For DevOps

🌐 1) What is an Operating System (OS)?

An Operating System (OS) is like the manager of your computer or mobile phone.

🧠 It controls everything — from running apps to managing hardware.

📱 Think of it like:

A smartphone has apps (games, camera, browser), but behind the scenes, Android or iOS helps them run.

🔧 Functions:

• 🧑‍💼 Manages hardware (CPU, memory, storage)

• 📂 Controls files and folders

• 🧩 Runs and manages apps

• 👥 Handles users and permissions

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💻 2) Client OS vs Server OS

• Client OS = Personal Use (like your laptop/phone)

• Server OS = Business Use (like running websites or apps for many people)

🐧 3) What is Linux OS?

Linux is a free, open-source operating system 🆓👨‍💻
It powers servers, desktops, Android phones, supercomputers, and more!

🔥 Why Linux is cool:

• 💸 Free to use

• 🔐 Secure and stable

• 🛠️ Used by developers, IT pros, and hackers!

• 🌍 Powers most of the Internet servers

🧑‍💻 Common Linux OS versions (called "distributions"):

• Ubuntu

• Fedora

• Debian

⚙️ 4) How Linux Works

Imagine Linux as a layered cake 🎂:

1. Hardware (CPU, RAM, etc.)

2. Kernel (heart of the OS) – talks to hardware 💬

3. Shell (command-line interface) – takes user input 👨‍💻

4. Applications – browsers, editors, etc. 📱

When you give a command ➡️ Linux passes it through the shell, and the kernel performs the task.

🔹 1) Application 📱

These are programs you run (like browsers, editors, terminal).

👉 They send tasks to the system (e.g., create a file, show files).

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🔹 2) Shell 💻

This is the middle layer (like a translator).

👉 It takes your commands (like ls, mkdir) and passes them to the kernel.

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🔹 3) Kernel 🧠

The core of Linux that talks to the hardware.

👉 It performs tasks like creating folders, reading files, using memory, etc.

🔁 Example Flow:

$mkdir myfolder

• ✅ App (terminal) → Shell understands it → Kernel creates the folder.

  App asks → Shell translates → Kernel executes ✅

5) Basic Linux Commands & Their Use

📝 What is Vim Editor?

Vim is a powerful text editor in Linux, used mostly from the terminal.
It helps you create and edit files — especially useful for coding, scripting, and config files.

✨ Think of it like Notepad, but for the terminal — and with superpowers!

🚀 Common Vim Commands

💡 How to Install Applications in Linux?

In Linux, we install apps using package managers (no .exe files like Windows).

🔧 Common Package Managers:

✅ General Steps to Install an App:

1. 🔄 Update package list

   sudo apt update

2. 📥 Install the app

   sudo apt install app-name

3. 🏁 Done! Run it by typing the app’s name.

🌐 How to Install Nginx Web Server

Let’s install Nginx on Ubuntu/Debian-based Linux.

💻 Commands:

sudo apt update # Step 1: Update package info

sudo apt install nginx # Step 2: Install nginx

▶️ Start and Enable Nginx:

sudo systemctl start nginx # Start the server now

sudo systemctl enable nginx # Start nginx on every boot

✅ Check if it’s working:

Open your browser and go to:

http://localhost

Or check with:

curl http://localhost

You should see:
“Welcome to nginx!” 🎉

🔥 Bonus Commands:

🧠 How Multiple Users Work at the Same Time in linux:

👥 Linux = Multi-User System

✅ How it works:

• Each user has a separate account 🧑‍💻

• Users can log in at the same time (locally or via SSH 🌐)

• Linux runs multiple tasks separately for each user ⚙️

• Permissions keep files private 🔐

• The kernel manages users and processes smoothly 🧠

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🧪 Example:

• User A works on terminal 1

• User B logs in remotely via SSH

• Both run different programs at the same time ✅

👤 1) How to Create a New User,Switch Users and Exit or Go Back