Beginner Guide for Docker Compose

Docker Compose lets you define and run multi-container applications in a single file and with one command.

Why Docker Compose?

One file: Describe all services, networks, and volumes in docker-compose.yml.
One command: docker compose up starts (and builds) everything.
Reproducible: Same file works on any machine with Docker and Compose.

Basic example

services:
  web:
    build: .
    ports:
      - "3000:3000"
    environment:
      - NODE_ENV=production
    depends_on:
      - db

  db:
    image: postgres:16-alpine
    environment:
      POSTGRES_USER: app
      POSTGRES_PASSWORD: secret
      POSTGRES_DB: app
    volumes:
      - db_data:/var/lib/postgresql/data

volumes:
  db_data:

Common commands

Command	Description
`docker compose up -d`	Start all services in the background
`docker compose down`	Stop and remove containers (add `-v` to remove volumes)
`docker compose ps`	List running services
`docker compose logs -f`	Follow logs from all services
`docker compose build`	Build images defined with `build:`

Key concepts

services: Each container (e.g. web, db) is a service.
build: Use build: . to build from a Dockerfile in the current directory.
image: Use image: name:tag to use a pre-built image.
ports: Map host port to container port ("HOST:CONTAINER).
environment: Set environment variables for the container.
volumes: Persist data; named volumes (e.g. db_data) are managed by Docker.
depends_on: Start order; wait for listed services to be started (not “healthy” unless you use condition).

Tips for beginners

Start with docker compose up (no -d) to see logs and Ctrl+C to stop.
Use docker compose config to validate your file.
Use depends_on with condition: service_healthy when a service must wait for another to be ready.
Put .env next to docker-compose.yml and reference variables with ${VAR}.

Once you’re comfortable, try adding a reverse proxy (e.g. Nginx) or multiple app services in the same Compose file.