Docker for Developers

Docker revolutionizes how we develop, ship, and run applications. Here's everything you need to get started.

Why Docker?

• Consistency - "Works on my machine" becomes "works everywhere"
• Isolation - Each app runs in its own container
• Portability - Deploy the same container anywhere
• Efficiency - Lighter than virtual machines

Basic Concepts

Images vs Containers

• Image: A blueprint (like a class)
• Container: A running instance (like an object)

Your First Dockerfile

# Use Node.js base image
FROM node:18-alpine

# Set working directory
WORKDIR /app

# Copy package files
COPY package*.json ./

# Install dependencies
RUN npm install

# Copy source code
COPY . .

# Expose port
EXPOSE 3000

# Start the app
CMD ["npm", "start"]

Essential Commands

# Build an image
docker build -t myapp .

# Run a container
docker run -p 3000:3000 myapp

# List running containers
docker ps

# Stop a container
docker stop <container_id>

# View logs
docker logs <container_id>

Docker Compose

Manage multi-container applications:

# docker-compose.yml
version: '3.8'

services:
 web:
 build: .
 ports:
 - "3000:3000"
 depends_on:
 - db

 db:
 image: postgres:14
 environment:
 POSTGRES_PASSWORD: secret
 volumes:
 - pgdata:/var/lib/postgresql/data

volumes:
 pgdata:

Run with:

docker-compose up -d

Development Workflow

Use bind mounts for hot reloading:

services:
 web:
 build: .
 volumes:
 - .:/app
 - /app/node_modules
 command: npm run dev

Best Practices

1. Use .dockerignore - Exclude node_modules, .git
2. Multi-stage builds - Smaller production images
3. Non-root user - Security best practice
4. Layer caching - Order Dockerfile commands wisely

Conclusion

Docker simplifies development and deployment. Start containerizing your projects today!