🐳 My Docker Learning Journey

From zero to containerizing Python, React, Node.js & full-stack MERN apps — my complete Docker beginner notes.

📺 Tutorial followed: Docker Masterclass by Adomic Arts

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📁 Project Structure

docker-demo/
├── Dockerfile        # My first Dockerfile — containerizing a Python app
├── python/
│   └── demo.py       # Python script that runs inside the container
└── html/
    └── ...           # HTML files copied into the container

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📚 What I Learned

🧱 1. What is Docker?

Docker packages your app and everything it needs into a container — it runs the same way on any machine. No more "it works on my computer" problems!

• A Docker Image = the blueprint / recipe
• A Docker Container = a running instance of that image
• Containers are NOT full operating systems like VMs — they run one specific task

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📄 2. Writing a Dockerfile

My very first Dockerfile (Python app):

FROM python

WORKDIR /user/app/src

COPY html /var/

COPY python/demo.py /user/app/src/

CMD ["python", "/user/app/src/demo.py"]

Instruction	What it does
FROM	Choose a base image to start from
WORKDIR	Set the working directory inside the container
COPY	Copy files from my machine into the container
RUN	Run a command while building the image
EXPOSE	Tell Docker which port the app uses
CMD	The command that runs when the container starts

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⚙️ 3. Essential Docker Commands

# Build an image from the Dockerfile
docker build -t image_name .

# Run a container
docker run --name container_name image_name

# Run in detached mode (background)
docker run --name container_name -d image_name

# List running containers
docker ps

# List ALL containers (including stopped)
docker ps -a

# Stop a running container
docker stop container_name

# Remove a stopped container
docker rm container_name

# List all images
docker images

# Remove an image (remove its containers first!)
docker rmi image_name

# Pull an image without running it
docker pull image_name

# Run a command inside a running container
docker exec container_name command

# Attach to a background container
docker attach container_id

# Remove EVERYTHING (containers, images, volumes)
docker system prune -a

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🌐 4. Port Mapping

To access an app running inside a container, map a host port to the container port:

docker run --name container_name -p 3000:5173 image_name
#                                    ↑       ↑
#                               host port  container port

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🏷️ 5. Image Versioning with Tags

Docker lets you version images using tags:

# Build with a tag
docker build -t image_name:v1 .

# Run a specific version
docker run --name container_name -p 3000:4000 image_name:v1

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📦 6. Docker Volumes — Persisting Data

Containers lose data when they stop. Volumes solve this by persisting data outside the container.

Types of Volumes:

Anonymous Volume — temporary, no name:

docker run -d --name my_container -v /app/data my_image

Named Volume — persists across restarts, shareable:

docker run -d --name my_container -v my_volume:/app/data my_image

Bind Mount (Host Volume) — maps a folder on your machine directly:

docker run -d --name my_container -v /path/on/host:/path/in/container my_image

Volume Commands:

docker volume create my_volume      # Create a volume
docker volume ls                    # List all volumes
docker volume inspect my_volume     # Inspect a volume
docker volume rm my_volume          # Remove a volume

Live Development with Volumes:

docker run --name container_name -p 3000:5173 --rm \
  -v /app/node_modules \
  -v ${PWD}:/app \
  -e CHOKIDAR_USEPOLLING=true \
  image_name

--rm automatically removes the container when it stops ✨

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🗂️ 7. .dockerignore

Like .gitignore — tells Docker what NOT to copy into the image. Speeds up builds and keeps sensitive files out:

node_modules
.env
.git

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🚀 8. Dockerizing Different Apps

Simple Node.js App

FROM node:20-alpine
WORKDIR /app
COPY package*.json ./
RUN npm install
COPY . .
EXPOSE 5000
CMD ["npm", "start"]

React App (Vite)

FROM node:20-alpine
WORKDIR /app
COPY package*.json ./
RUN npm install
COPY . .
EXPOSE 5173
CMD ["npm", "run", "dev"]

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🏗️ 9. Docker Compose — Multi-Container Apps

Docker Compose lets you define and run multiple containers together using a single docker-compose.yml file.

Example — Full Stack MERN app with MongoDB + API + Client:

services:
  mongo:
    image: mongo:latest
    container_name: mongo_container
    volumes:
      - mongo_data:/data/db
    ports:
      - "27017:27017"

  api:
    build: ./api
    container_name: api_container
    ports:
      - "5000:5000"
    depends_on:
      - mongo
    volumes:
      - ./api:/app
      - /app/node_modules
    environment:
      - MONGO_URL=mongodb://mongo:27017/test-users

  client:
    build: ./client
    container_name: client_container
    ports:
      - "3000:3000"
    depends_on:
      - api
    stdin_open: true
    tty: true
    volumes:
      - ./client:/app
      - /client/node_modules

volumes:
  mongo_data:

depends_on ensures services start in the right order 🔗

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☁️ 10. Pushing Images to Docker Hub

Share your images with the world!

docker login
docker tag image_name dockerhub_username/image_name:tag
docker push dockerhub_username/image_name:tag

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🗺️ My Learning Path

What is Docker?
      ↓
Write first Dockerfile (Python app)
      ↓
docker build & docker run
      ↓
Port mapping for web apps
      ↓
Image versioning with tags
      ↓
Docker Volumes for data persistence
      ↓
Dockerize React & Node apps
      ↓
Docker Compose for MERN stack 🎉
      ↓
Push to Docker Hub ☁️

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🔜 What's Next

• Docker networking (custom networks between containers)
• Multi-stage builds for smaller production images
• Docker secrets for managing sensitive data
• Introduction to Kubernetes

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🏆 Certificate

This repo is part of my Docker learning journey. I successfully completed the Crash Course: Docker For Absolute Beginners on KodeKloud!

Field	Details
🎓 Course	Crash Course: Docker For Absolute Beginners
🏫 Platform	KodeKloud
👤 Instructor	Mumshad Mannambeth (Founder & Trainer)
📅 Completed	July 16, 2026
🪪 Certificate ID	4db32d82-07f0-49b9-9ef2-27db18123a7a

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📖 Resources

• 📺 Full Tutorial by Adomic Arts
• 🎓 KodeKloud — Docker For Absolute Beginners
• 📝 Official Docker Docs
• 🐳 Docker Hub

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This is my first Docker experience — built with curiosity, lots of terminal errors, and even more learning! 🚀