# 📘 DevOps Week 2 – Linux OS Fundamentals & Shell Scripting

* * *

## 🔹 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)

```plaintext
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?

```plaintext
touch file.txt
```

👉 Creates empty file

* * *

## 🔹 4. List Files & Folders

```plaintext
ls
```

👉 Shows all files

* * *

## 🔹 5. `man` Command

```plaintext
man ls
```

👉 Shows manual/help of command

* * *

## 🔹 6. vi / vim Editor (Write File)

```plaintext
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

| touch | vim |
| --- | --- |
| Creates file only | Create + edit file |
| No content | Can write content |

* * *

## 🔹 8. Copy Content in Linux

```plaintext
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

| Shell | Use |
| --- | --- |
| bash | Most common |
| ksh | Advanced scripting |
| dash | Lightweight & fast |

* * *

## 🔹 11. Insert Command (vim)

*   Press `i` → enter insert mode
    
*   Start writing
    

* * *

## 🔹 12. echo Command

```plaintext
echo "Hello"
```

👉 Print output

* * *

## 🔹 13. Execute Shell Script

```plaintext
./script.sh
```

* * *

## 🔹 14. Grant Permissions

```plaintext
chmod +x script.sh
```

👉 Makes script executable

* * *

## 🔹 15. chmod Command

```plaintext
chmod 777 file.txt
```

👉 Change file permissions

* * *

## Permission Types:

*   r = read
    
*   w = write
    
*   x = execute
    

* * *

## 🔹 16. Check Command History

```plaintext
history
```

👉 Shows previously used commands

* * *

## 🔹 17. Create Folder

```plaintext
mkdir foldername
```

* * *

## 🔹 18. Change Directory

```plaintext
cd foldername
```

* * *

## 🔹 19. Simple Shell Script

```plaintext
#!/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

```plaintext
free -h
```

👉 Shows RAM

* * *

```plaintext
lscpu
```

👉 Shows CPU info

* * *

## 🔹 22. Top Command

```plaintext
top
```

👉 Shows:

*   Running processes
    
*   CPU usage
    
*   Memory usage
    

![](https://cdn.hashnode.com/uploads/covers/66fecde7cb0abd844c1a2f3c/0e2d13e2-72d3-46cb-9a2f-ce39f4485674.png align="center")

* * *

## 📘 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)

```bash
#!/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

```bash
echo "Checking CPU usage..."
echo "Checking Memory..."
```

👉 Helps understand output clearly

* * *

### 🔹 5. Debug Mode

```bash
set -x
```

👉 Shows:

*   Each command before execution
    

👉 Used for debugging

* * *

### 🔹 6. What are Processes?

*   Process = Running program
    

### ✔ List Processes:

```bash
ps
```

### ✔ Find Process ID:

```bash
ps -ef
```

* * *

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

### ✔ Pipe:

*   Pass output of one command → another
    

```bash
ps -ef | grep nginx
```

👉 Find specific process

* * *

## 🎯 Interview Point:

👉 Pipe = connects multiple commands

* * *

### 🔹 8. AWK Command

*   Used for:
    
    *   Filtering
        
    *   Extracting specific columns
        

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

👉 Prints process ID

* * *

### 🔹 9. set -e (Error Handling)

```bash
set -e
```

👉 Script stops if error occurs

* * *

### 🔹 10. set -o pipefail

```bash
set -o pipefail
```

👉 If any command in pipeline fails → script fails

👉 Important for production scripts

* * *

### 🔹 11. DevOps Use Case: Search Errors in Logs

```bash
grep "error" logfile.txt
```

👉 Used to:

*   Debug issues
    
*   Find failures
    

* * *

### 🔹 12. wget Command

```bash
wget <url>
```

👉 Download files from internet

* * *

### 🔹 13. CURL vs WGET

| CURL | WGET |
| --- | --- |
| API calls | File download |
| More flexible | Simple download |

* * *

### 🔹 14. find Command

```bash
find . -name "file.txt"
```

👉 Search files

* * *

### 🔹 15. sudo vs su

| Command | Use |
| --- | --- |
| sudo | Run as admin |
| su | Switch user |

* * *

### 🔹 16. If-Else in Shell

```bash
if [ $a -gt $b ]
then
 echo "A is greater"
else
 echo "B is greater"
fi
```

* * *

### 🔹 17. For Loop

```bash
for i in 1 2 3
do
 echo $i
done
```

![](https://cdn.hashnode.com/uploads/covers/66fecde7cb0abd844c1a2f3c/6c70b96e-5a97-4568-b46e-c2086285f2ee.png align="center")

📘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:

```bash
aws s3 ls
```

✔ EC2 Instances:

```bash
aws ec2 describe-instances
```

✔ Lambda:

```bash
aws lambda list-functions
```

✔ IAM Users:

```bash
aws iam list-users
```

* * *

## 🔹 4. Debug Mode

```bash
set -x
```

👉 Used to debug script

* * *

## 🔹 5. JSON Parsing using JQ

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

👉 Extract specific data from JSON

* * *

## 🔹 6. Automation using Cron Job

```bash
crontab -e
```

👉 Schedule script

## ✔ Example:

```bash
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](https://github.com/hritikranjan1/shell-scripting-projects.git)

![](https://cdn.hashnode.com/uploads/covers/66fecde7cb0abd844c1a2f3c/2cb2ec19-6ae0-470c-854d-3804967d9e5a.png align="center")

* * *

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

![](https://cdn.hashnode.com/uploads/covers/66fecde7cb0abd844c1a2f3c/a529de49-1c62-449d-8bcb-fb3717992a85.png align="center")

* * *

### 🔹 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:
    

```bash
kubectl get pods
```

* * *

✔ API (Application Programming Interface)

*   Communicate with apps using:
    
    *   HTTP requests
        
    *   JSON data
        

👉 Example:

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

* * *

## 🎯 Difference:

| CLI | API |
| --- | --- |
| Easy to use | More flexible |
| Limited control | Full control |
| Manual usage | Automation friendly |

* * *

## 🔹 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:

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

* * *

## ✔ Parsing Data:

```bash
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

| Git | GitHub |
| --- | --- |
| Tool | Platform |
| Local system | Cloud |
| Version control | Collaboration |

* * *

## 🔹 8. Git Basic Workflow (Very Important 🔥)

👉 Git lifecycle:

```text
Working Directory → Staging → Repository
```

* * *

## ✔ Commands:

### 1\. Initialize repo

```bash
git init
```

* * *

### 2\. Check status

```bash
git status
```

* * *

### 3\. Add files

```bash
git add .
```

* * *

### 4\. Commit changes

```bash
git commit -m "message"
```

* * *

### 5\. View history

```bash
git log
```

* * *

### 6\. See changes

```bash
git diff
```

* * *

## 🔹 9. Push Code to GitHub

```bash
git push
```

👉 Upload local code to GitHub

* * *

## 🔹 10. Clone vs Fork

## ✔ Clone:

```bash
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)

```text
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
    

* * *

![](https://cdn.hashnode.com/uploads/covers/66fecde7cb0abd844c1a2f3c/cdf6b0c1-a817-4c70-a43e-55fba87a3cf8.png align="center")

* * *

# 🚀 Continue Your Learning Journey

Thank you for taking the time to read this article.

Technology is evolving rapidly, and continuous learning is one of the most valuable investments you can make in your career. Whether you're exploring **DevOps, Cloud Computing, Artificial Intelligence, Cybersecurity, Software Development, Data Science, or Career Growth**, the resources below can help you deepen your knowledge and stay ahead in the industry.

* * *

# 🎓 Recommended Learning Platforms

## 🚀 Coursera

Learn from world-renowned universities and industry leaders including Google, IBM, Stanford, Microsoft, Meta, and many more.

✔ Professional Certificates ✔ Career-focused Learning Paths ✔ AI & Machine Learning Programs ✔ Cloud & DevOps Certifications ✔ Business & Leadership Courses

🔗 https://imp.i384100.net/k0KvbV

* * *

## 💻 Udemy

One of the largest online learning platforms with practical, hands-on courses covering:

✔ DevOps & Kubernetes ✔ Docker & Cloud Computing ✔ AWS, Azure & GCP ✔ Programming & Development ✔ Cybersecurity & Ethical Hacking

🔗 https://trk.udemy.com/MAL2MY

* * *

## 📊 DataCamp

A great platform for anyone interested in:

✔ Python Programming ✔ SQL & Databases ✔ Data Analytics ✔ Machine Learning ✔ Artificial Intelligence

Interactive learning paths and hands-on projects make it ideal for beginners and professionals alike.

🔗 https://datacamp.pxf.io/nX4kER

* * *

## 🎓 edX

Access high-quality courses and certifications from leading institutions such as:

✔ Harvard University ✔ MIT ✔ Berkeley ✔ Microsoft

Perfect for learners seeking university-level education online.

🔗 https://edx.sjv.io/POvVeN

* * *

## 🎨 Domestika

Enhance your creative skills with courses on:

✔ Graphic Design ✔ Video Editing ✔ Animation ✔ Digital Marketing ✔ Content Creation

🔗 https://domestika.sjv.io/dynKAW

* * *

# 🛠️ Recommended Tools & Resources

## 🔥 AppSumo

Discover exclusive lifetime deals on:

✔ AI Tools ✔ Productivity Software ✔ Developer Utilities ✔ Marketing Platforms ✔ Business Applications

A must-have resource for developers, creators, freelancers, and entrepreneurs looking to save money while accessing premium tools.

🔗 https://appsumo.8odi.net/L04a33

* * *

## 🛒 Shopify

Looking to start an online business or launch an eCommerce store?

Shopify provides everything you need to build, manage, and scale an online business.

✔ Online Store Builder ✔ Payment Integration ✔ Inventory Management ✔ Marketing Tools

🔗 https://shopify.pxf.io/Vxv09k

* * *

## 🌐 WordPress, WooCommerce & Jetpack

Create professional websites, blogs, and online stores with one of the most trusted web ecosystems in the world.

Ideal for:

✔ Personal Blogs ✔ Portfolio Websites ✔ Business Websites ✔ eCommerce Stores

🔗 https://automattic.pxf.io/Z6vR5W

* * *

# 🌍 Language Learning Resources

## 🗣️ Preply

Learn English and other languages through personalized one-on-one tutoring sessions with experts from around the world.

🔗 https://preply.sjv.io/o4gBDY

* * *

## 📚 British Council English Online

Improve your professional communication skills and English fluency through structured learning programs.

🔗 https://englishonline.sjv.io/9VOGa4

* * *

## 🧠 Rosetta Stone

One of the most recognized language-learning platforms for immersive language acquisition.

🔗 https://aff.rosettastone.com/X4OyqG

* * *

# 🧪 Science & Educational Resources

## 🔬 MEL Science

Interactive science kits and educational experiences designed to make STEM learning engaging and practical.

🔗 https://imp.i328067.net/bk2beg

* * *

## 📖 Carson Dellosa Education

Educational materials and learning resources for students, teachers, and lifelong learners.

🔗 https://carsondellosaeducation.sjv.io/E0JbjW

* * *

# ❤️ Support My Work

Creating detailed technical content, tutorials, guides, and learning resources takes significant time and effort.

If you find my articles helpful and would like to support my work, you can do so through the following platforms:

## ⭐ Become a GitHub Sponsor

Support my open-source contributions, technical content, and community projects.

🔗 https://github.com/sponsors/hritikranjan1

* * *

## ☕ Buy Me a Chai

Enjoying my content? Consider buying me a chai and supporting future tutorials, guides, and educational resources.

🔗 https://www.chai4.me/hritikranjan

* * *

# 👨‍💻 Connect With Me

**Hritik Ranjan**

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

### Connect & Follow

🔗 GitHub: https://github.com/hritikranjan1

🔗 LinkedIn: https://linkedin.com/in/hritikranjan1

* * *

## 📢 Found This Article Helpful?

If this article added value to your learning journey:

✅ Share it with your network  
✅ Bookmark it for future reference  
✅ Follow for more DevOps, AI, Cloud, Cybersecurity, and Software Engineering content

Thank you for reading and being part of this learning journey.

**Keep Learning. Keep Building. Keep Growing. 🚀**