Docker for Developers: Complete Guide

Introduction

Docker has revolutionized application deployment. Learn how to containerize your applications effectively.

1. Docker Basics

Dockerfile Example

FROM node:18-alpine

WORKDIR /app

COPY package*.json ./
RUN npm ci --only=production

COPY . .

EXPOSE 3000
CMD ["npm", "start"]

2. Multi-Stage Builds

# Build stage
FROM node:18-alpine AS builder
WORKDIR /app
COPY package*.json ./
RUN npm ci
COPY . .
RUN npm run build

# Production stage
FROM node:18-alpine
WORKDIR /app
COPY --from=builder /app/dist ./dist
COPY --from=builder /app/node_modules ./node_modules
EXPOSE 3000
CMD ["node", "dist/index.js"]

3. Docker Compose

version: '3.8'

services:
  app:
    build: .
    ports:
      - "3000:3000"
    environment:
      - DATABASE_URL=postgresql://db:5432/myapp
    depends_on:
      - db

  db:
    image: postgres:15-alpine
    environment:
      POSTGRES_DB: myapp
      POSTGRES_PASSWORD: password
    volumes:
      - postgres_data:/var/lib/postgresql/data

volumes:
  postgres_data:

4. Best Practices

• •Use .dockerignore
• •Minimize layer count
• •Use specific image tags
• •Don't run as root
• •Use health checks

Conclusion

Docker simplifies deployment and ensures consistency across environments.