🔹 1. What is an Operating System (OS)?

• OS = Interface between Hardware & Software

👉 It acts as a bridge:

• Hardware (CPU, RAM, Disk)

• Software (Applications, Programs)

🎯 Functions of OS:

• Process management

• Memory management

• File system management

• Device control

👉 Example OS:

• Linux

• Windows

• macOS

🔹 2. What is Linux?

• Linux = Open-source Operating System

• Widely used in:

  • Servers

  • Cloud (AWS, Azure)

  • DevOps

✔ Why Linux is Important

• Free & open source

• Secure

• Lightweight

• Most servers run on Linux

🔹 3. Linux Architecture (Basic Idea)

User → Shell → Kernel → Hardware

✔ Components:

• Kernel → Core of OS (controls hardware)

• Shell → Interface to interact with system

• File System → Organizes data

🔹 4. What is Shell?

• Shell = Command Line Interface (CLI)

👉 It allows:

• Running commands

• Managing files

• Executing scripts

✔ Types of Shell:

• Bash (most common)

• Sh

• Zsh

📘 Linux & Shell Scripting

🔹 1. Introduction

• This video teaches:

  • Basic Linux commands

  • File handling

  • Shell scripting basics

  • Automation concepts

👉 Focus: Learn Linux + start scripting

🔹 2. Purpose of Scripting & Automation

• Instead of doing tasks manually:
  👉 Use scripts to automate

✔ Example:

• Backup files

• Run multiple commands at once

👉 Benefit:

• Saves time

• Reduces errors

🔹 3. How to Create a File?

touch file.txt

👉 Creates empty file

🔹 4. List Files & Folders

ls

👉 Shows all files

🔹 5. man Command

man ls

👉 Shows manual/help of command

🔹 6. vi / vim Editor (Write File)

vim file.txt

👉 Used to:

• Create file

• Edit file

Modes in vim:

• Insert mode → write text

• Command mode → run commands

🔹 7. Difference: touch vs vim

🔹 8. Copy Content in Linux

cp file1 file2

👉 Copy file

🔹 9. #!/bin/bash or #!/bin/sh

• Called Shebang

👉 Purpose:

• Tells system: 👉 Which shell to use to run script

🔹 10. Difference: bash, ksh, dash

🔹 11. Insert Command (vim)

• Press i → enter insert mode

• Start writing

🔹 12. echo Command

echo "Hello"

👉 Print output

🔹 13. Execute Shell Script

./script.sh

🔹 14. Grant Permissions

chmod +x script.sh

👉 Makes script executable

🔹 15. chmod Command

chmod 777 file.txt

👉 Change file permissions

Permission Types:

• r = read

• w = write

• x = execute

🔹 16. Check Command History

history

👉 Shows previously used commands

🔹 17. Create Folder

mkdir foldername

🔹 18. Change Directory

cd foldername

🔹 19. Simple Shell Script

#!/bin/bash
echo "Hello World"

🔹 20. Purpose of Shell Scripting in DevOps

• Automate tasks

• Deploy applications

• Run pipelines

👉 Very important in DevOps

🔹 21. Check CPU & RAM

free -h

👉 Shows RAM

lscpu

👉 Shows CPU info

🔹 22. Top Command

top

👉 Shows:

• Running processes

• CPU usage

• Memory usage

📘 Node Health, Debugging, Pipes, AWK, Advanced Scripting

🔹 1. DevOps Use Case: Node Health Check

👉 Goal: Check if a server (node) is healthy or not

✔ What to check:

• CPU usage

• Memory (RAM)

• Disk space

• Running processes

🔹 2. Sample Node Health Script (Basic Idea)

#!/bin/bash
echo "Checking system health..."
top
free -h
df -h

👉 This script checks:

• CPU → top

• RAM → free -h

• Disk → df -h

🔹 3. Good Practices in Scripting

• Use clear variable names

• Add comments

• Use echo statements

• Handle errors properly

👉 Makes script readable & professional

🔹 4. Improve Script Readability

echo "Checking CPU usage..."
echo "Checking Memory..."

👉 Helps understand output clearly

🔹 5. Debug Mode

set -x

👉 Shows:

• Each command before execution

👉 Used for debugging

🔹 6. What are Processes?

• Process = Running program

✔ List Processes:

ps

✔ Find Process ID:

ps -ef

🔹 7. grep & Pipe (|) – VERY IMPORTANT 🔥

✔ Pipe:

• Pass output of one command → another

ps -ef | grep nginx

👉 Find specific process

🎯 Interview Point:

👉 Pipe = connects multiple commands

🔹 8. AWK Command

• Used for:

  • Filtering

  • Extracting specific columns

ps -ef | awk '{print $2}'

👉 Prints process ID

🔹 9. set -e (Error Handling)

set -e

👉 Script stops if error occurs

🔹 10. set -o pipefail

set -o pipefail

👉 If any command in pipeline fails → script fails

👉 Important for production scripts

🔹 11. DevOps Use Case: Search Errors in Logs

grep "error" logfile.txt

👉 Used to:

• Debug issues

• Find failures

🔹 12. wget Command

wget <url>

👉 Download files from internet

🔹 13. CURL vs WGET

🔹 14. find Command

find . -name "file.txt"

👉 Search files

🔹 15. sudo vs su

🔹 16. If-Else in Shell

if [ \(a -gt \)b ]
then
 echo "A is greater"
else
 echo "B is greater"
fi

🔹 17. For Loop

for i in 1 2 3
do
 echo $i
done

📘AWS Resource Tracker Project

🔹 1. Project Goal

👉 Build script to:

• Track AWS resources

• Reduce cost

✔ Why Important?

Cloud = Pay-as-you-go

• Unused resources = Money waste

👉 Example:

• Unused EC2

• Orphaned EBS

🔹 2. Tools Used

• AWS CLI

• Bash scripting

• Cron jobs

🔹 3. Resource Tracking Commands

✔ S3 Buckets:

aws s3 ls

✔ EC2 Instances:

aws ec2 describe-instances

✔ Lambda:

aws lambda list-functions

✔ IAM Users:

aws iam list-users

🔹 4. Debug Mode

set -x

👉 Used to debug script

🔹 5. JSON Parsing using JQ

jq '.Reservations[].Instances[].InstanceId'

👉 Extract specific data from JSON

🔹 6. Automation using Cron Job

crontab -e

👉 Schedule script

✔ Example:

0 9 * * * /home/script.sh

👉 Runs daily at 9 AM

🔹 7. Full Workflow

1. Write script

2. Fetch AWS data

3. Filter using JQ

4. Generate report

5. Automate using cron

🔹 8. Real DevOps Use Case

👉 Companies use this to:

• Track unused resources

• Save cost

• Monitor infrastructure

Project link - https://github.com/hritikranjan1/shell-scripting-projects.git

📘 Git, GitHub, Branching & GitHub API (Simple Flow)

🔹 1. Problem Statement (Real DevOps Scenario)

As a DevOps Engineer 👇

• You manage multiple repositories

• Many users have access

👉 Problem:

• Checking access manually from GitHub UI is slow & inefficient

• Especially during employee offboarding

👉 Solution:

• Use GitHub API + Automation Script

🔹 2. API vs CLI (Important Concept)

✔ CLI (Command Line Interface)

• Direct commands in terminal 👉 Example:

kubectl get pods

✔ API (Application Programming Interface)

• Communicate with apps using:

  • HTTP requests

  • JSON data

👉 Example:

curl https://api.github.com/repos

🎯 Difference:

🔹 3. GitHub API Integration (Main Concept)

👉 GitHub provides APIs to:

• Get repo details

• List users

• Check PRs & issues

✔ How it works:

1. Send request using curl

2. Get response in JSON

3. Filter using jq

📌 Example:

curl https://api.github.com/repos/user/repo

✔ Parsing Data:

jq '.[] | .login'

👉 Extract useful data from JSON

🔹 4. Script Flow (Project)

👉 Steps used in video:

1. Clone script

2. Add GitHub token (for authentication)

3. Run script

4. Fetch repo data

5. Filter users

6. Show authorized users

✔ Tools Used:

• curl

• jq

• Bash scripting

✔ Improvement Tips:

• Use functions

• Add comments

• Handle errors

🔹 5. Introduction to Version Control (VCS)

👉 VCS = Track changes in code

✔ Why we need VCS?

• Multiple developers work together

• Track changes/history

• Go back to old version

🔹 6. Types of Version Control

✔ Centralized (Old)

• Example: SVN

• One central server

👉 Problem:

• If server down → work stops

✔ Distributed (Git)

• Each user has full copy

👉 Benefit:

• Work even offline

🔹 7. Git vs GitHub

🔹 8. Git Basic Workflow (Very Important 🔥)

👉 Git lifecycle:

Working Directory → Staging → Repository

✔ Commands:

1. Initialize repo

git init

2. Check status

git status

3. Add files

git add .

4. Commit changes

git commit -m "message"

5. View history

git log

6. See changes

git diff

🔹 9. Push Code to GitHub

git push

👉 Upload local code to GitHub

🔹 10. Clone vs Fork

✔ Clone:

git clone <repo-url>

👉 Download repo locally

✔ Fork:

👉 Copy repo on GitHub

👉 Used for:

• Open-source contribution

🔹 11. Branching Concept (VERY IMPORTANT 🔥)

✔ Why Branching?

• Work on new feature safely

• Don’t break main code

✔ Main Branch:

• main / master 👉 Production-ready code

✔ Other Branches:

• Feature Branch → New feature

• Release Branch → Prepare release

• Hotfix Branch → Fix urgent bug

🔹 12. Branch Workflow

👉 Steps:

1. Create branch

2. Work on feature

3. Test code

4. Merge to main

🔹 13. Merge Strategies

✔ Git Merge

• Combine branches

• Keeps history

✔ Git Rebase

• Clean linear history

👉 Preferred in large projects

✔ Git Cherry-pick

• Copy specific commit

🔹 14. Git Lifecycle (Full Flow)

git init → git add → git commit → git push

🔹 15. Important Git Commands

• git pull → Get latest code

• git remote → Manage repo link

• git branch → Show branches

🔹 16. Real DevOps Workflow

1. Developer writes code

2. Create feature branch

3. Commit changes

4. Push to GitHub

5. Create PR (Pull Request)

6. Review & merge

🔹 17. Key Takeaways

• Git = Version control

• GitHub = Collaboration platform

• Branching = Safe development

• API = Automation

• Scripts = Save time

🚀 Continue Your Learning Journey

Thank you for taking the time to read this article.

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💡 AI Enthusiast ☁️ DevOps Learner 🔐 Cybersecurity Advocate 💻 Software Developer

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