🚀 Master Docker: A DevOps-Grade Tutorial for Developers and Engineers 🐳

📌 Why Docker?

Docker eliminates "it works on my machine" problems by containerizing apps along with their environments. It’s the backbone of modern DevOps, enabling reproducible builds, fast deployments, and scalable infrastructure.

Whether you're building microservices, APIs, frontends, or full-stack SaaS apps—Docker is essential.

🔧 Prerequisites:
✅ Basic CLI knowledge
✅ A project or app to test Docker with (Node.js used here, but language doesn't matter)

🛠️ 1. Install Docker

🖥️ macOS / Windows
➡️ Install Docker Desktop: https://www.docker.com/products/docker-desktop

sudo apt update
sudo apt install docker.io -y
sudo systemctl start docker
sudo systemctl enable docker

Verify
docker --version

🐳 2. Understand Docker’s Core Concepts

Concept	Description
Image	A blueprint of your app (like a class)
Container	A running instance of an image
Dockerfile	Instructions to build your image
Volume	Persistent storage for containers
Network	Allows containers to communicate
Registry	Stores images (like Docker Hub or GitHub Container Registry)

🚀 3. Running Your First Container

docker run hello-world
Explanation:

• Pulls the hello-world image
• Runs it inside a new container
• Shows a success message

🧱 4. Create and Use a Dockerfile

Step-by-step: Let's Dockerize a Node.js app.
Project:

mkdir myapp && cd myapp
npm init -y
npm i express
echo "require('express')().listen(3000)" > index.js

DockerFile :

# Base image
FROM node:18

# Set working directory
WORKDIR /app

# Copy files
COPY package*.json ./
RUN npm install
COPY . .

# Expose and run
EXPOSE 3000
CMD ["node", "index.js"]

Build and Run:

docker build -t myapp .
docker run -p 3000:3000 myapp

📦 5. Use Volumes (Dev Mode)

So changes reflect without rebuilds:

docker run -p 3000:3000 -v $(pwd):/app myapp

🔁 6. Docker Compose – Multi-Container Apps

Example: Node.js app + MongoDB

<pre>
version: '3.9'
services:
  app:
    build: .
    ports:
      - "3000:3000"
    volumes:
      - .:/app
    environment:
      - NODE_ENV=development
    depends_on:
      - mongo

  mongo:
    image: mongo
    volumes:
      - mongodata:/data/db
    ports:
      - "27017:27017"

volumes:
  mongodata:

</pre>

*** Run: ***

docker-compose up --build

💡7. Multi-Stage Docker Builds

Reduce image size and isolate build from production:

# Stage 1: Build
FROM node:18 AS builder
WORKDIR /app
COPY . .
RUN npm install && npm run build

# Stage 2: Runtime
FROM node:18-slim
WORKDIR /app
COPY --from=builder /app/dist .
CMD ["node", "server.js"]

🧰 8. Helpful Docker Commands

docker ps -a                 # List all containers
docker images                # List images
docker logs <container>      # Logs
docker exec -it <container> bash  # Enter container
docker stop <id>             # Stop container
docker rm <id>               # Remove container
docker rmi <image>           # Remove image

🔐 9. Docker Security Best Practices

✅ Use minimal base images (alpine, node:slim)
✅ Use .dockerignore like .gitignore
✅ Run as non-root if possible
✅ Use image scanning tools:

docker scout quickview
# or
trivy image myapp

🔄 10. Real DevOps CI/CD with Docker

GitHub Actions Example:

<pre>
name: Docker CI

on:
  push:
    branches: [ main ]

jobs:
  build:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v3
      - name: Build Docker image
        run: docker build -t myorg/myapp:${{ github.sha }} .

      - name: Push to Docker Hub
        run: |
          echo "${{ secrets.DOCKER_PASS }}" | docker login -u ${{ secrets.DOCKER_USER }} --password-stdin
          docker push myorg/myapp:${{ github.sha }}
</pre>

🧪 11. Advanced Real-World Scenarios

📌 Run PostgreSQL + Adminer for Dev:

services:
  db:
    image: postgres
    environment:
      POSTGRES_PASSWORD: pass

  adminer:
    image: adminer
    ports:
      - "8080:8080"

🧩 Host React or Next.js with Nginx:

FROM node:18 AS builder
WORKDIR /app
COPY . .
RUN npm install && npm run build

FROM nginx:alpine
COPY --from=builder /app/build /usr/share/nginx/html

🧼 12. Clean Up Resources

docker system prune -a
docker volume prune
docker image prune

🧠 Conclusion: Docker is DevOps

Once you’ve mastered Docker:

• Build fast, reproducible workflows
• Deploy secure, production-ready images
• Use in CI/CD pipelines
• Plug into Kubernetes or serverless platforms

💬 Want More?

Let me know in the comments if you want a follow-up:

• 🧭 Kubernetes for Docker users
• 🛠️ Docker + Ansible + Terraform workflow
• 🧠 Docker debugging & profiling tools

🧑‍💻 Connect With Me

📺 YouTube: Codewithimran
🐙 GitHub: Codewithimran
💡 LinkedIn: Codewithimran