"Install PostgreSQL, then Redis, then Elasticsearch, configure these 12 environment variables, make sure you're on Node 20 not 18, and oh — the tests need Python 3.11."

Sound like your onboarding doc? Here's the Docker version: docker compose up. Done. New dev writes code in 15 minutes.

The 3 Commands That Cover 80% of Docker

You don't need to learn everything. Start here:

# Run any service instantly
docker run -d -p 8080:80 nginx:latest

# Build your own app into an image
docker build -t my-app:1.0 .

# Start your entire stack (app + db + cache)
docker compose up -d

Open http://localhost:8080 after the first command — you'll see Nginx running. No install, no config, no conflicts.

Your First Dockerfile (Copy This)

A Dockerfile is a recipe for turning your code into a container. Here's one for a Node.js app:

FROM node:20-alpine
WORKDIR /app
COPY package*.json ./
RUN npm ci --only=production
COPY . .
EXPOSE 3000
CMD ["node", "server.js"]

The trick: COPY package*.json before COPY . . means Docker caches your npm ci step. Change your code? Rebuild takes 2 seconds instead of 30.

Build it: docker build -t my-app:1.0 .
Run it: docker run -d -p 3000:3000 my-app:1.0

For Python/Flask, same pattern:

FROM python:3.12-slim
WORKDIR /app
COPY requirements.txt .
RUN pip install --no-cache-dir -r requirements.txt
COPY . .
EXPOSE 5000
CMD ["python", "app.py"]

Docker Compose: The Real Power

Your app needs a database and Redis? One file, one command:

version: "3.9"
services:
  app:
    build: .
    ports:
      - "3000:3000"
    environment:
      DATABASE_URL: postgres://user:pass@db:5432/mydb
      REDIS_URL: redis://cache:6379
    depends_on:
      - db
      - cache

  db:
    image: postgres:16-alpine
    environment:
      POSTGRES_USER: user
      POSTGRES_PASSWORD: pass
      POSTGRES_DB: mydb
    volumes:
      - pgdata:/var/lib/postgresql/data

  cache:
    image: redis:7-alpine

volumes:
  pgdata:

docker compose up -d        # start everything
docker compose down          # stop everything
docker compose up -d --build # rebuild after code changes
docker compose down -v       # stop + delete database data

The pgdata volume means your database survives container restarts. Remove it with -v only when you want a fresh start.

The 10 Commands Cheat Sheet

Before You Deploy: Quick Checklist

• ✅ Using alpine or slim base image (not the 1 GB default)
• ✅ .dockerignore excludes node_modules, .git, .env
• ✅ Container runs as non-root (USER node)
• ✅ Secrets passed via environment, never hardcoded
• ✅ Volumes configured for database data
• ✅ Health check added: HEALTHCHECK CMD curl -f http://localhost:3000/health || exit 1
• ✅ Tested with docker compose up on a clean machine

Common Gotchas

"My container exits immediately." Your app probably crashes on startup. Check logs: docker logs my-app. Most common cause: missing environment variable that's set on your machine but not in the container.

"Database is empty after restart." You forgot the volume. Without volumes: in docker-compose.yml, data lives inside the container and dies with it.

"Port already in use." Something else is running on that port. Either stop it or change the host port: -p 3001:3000 maps host port 3001 to container port 3000.

"Image is 1.2 GB." Use node:20-alpine instead of node:20. Add .dockerignore. Use multi-stage builds for compiled languages. Typical reduction: 1 GB → 100 MB.

📖 The full guide covers installation walkthroughs for Windows/macOS/Linux, Python Dockerfile examples, Docker Desktop licensing (free vs paid), multi-stage builds, and a production-readiness checklist.

Read the full article on trackstack.tech →