Docker Compose Beginner Guide: Run Multi-Container Apps with compose.yaml

Docker Compose Beginner Guide#

Docker Compose helps you define and run multi-container applications using a single YAML file. This guide explains services, ports, volumes, networks, environment variables, commands, and beginner examples.

What is Docker Compose?#

Docker Compose lets you describe multiple services in a compose.yaml file and start them together with one command.

Basic compose.yaml#

services: web: image: nginx:alpine ports: - "8080:80"

Run the app#

docker compose up -d docker compose ps docker compose logs web docker compose down

App with database example#

services: app: image: node:20-alpine working_dir: /app volumes: - .:/app command: sh -c "npm install && npm start" ports: - "3000:3000" environment: DATABASE_HOST: db depends_on: - db db: image: postgres:16 environment: POSTGRES_DB: appdb POSTGRES_USER: appuser POSTGRES_PASSWORD: example volumes: - db_data:/var/lib/postgresql/data volumes: db_data:

Important Compose concepts#

• services define containers.
• ports publish container ports to the host.
• volumes persist data or mount local files.
• environment passes environment variables.
• depends_on controls startup order, not full readiness.
• Service names become DNS names inside the Compose network.

Useful commands#

docker compose up docker compose up -d docker compose down docker compose logs -f docker compose ps docker compose exec app sh docker compose pull docker compose build

Common mistakes#

• Thinking depends_on means the database is fully ready.
• Committing real passwords in compose files.
• Forgetting named volumes for database data.
• Using Compose production files without reviewing secrets and ports.
• Not checking logs when services fail.

Best practices#

• Use Compose for local development and small environments.
• Use named volumes for database state.
• Use .env carefully and do not commit secret values.
• Keep service names clear.
• Use separate override files for local-only settings.

Related Melochip guides#

• Docker Learning Path
• Docker Volumes Explained
• Docker Networks Explained

Official references#

• Docker Compose documentation
• Compose file reference