What is Docker Compose?

Tool for defining and running multi-container Docker applications. Allows describing services, networks, and volumes in a single YAML file and launching them with one command.

Main features:

• Defining multiple services in one file.
• Creating and starting all services with one command.
• Managing the application lifecycle (start, stop, restart, scaling).
• Network interaction between containers.
• Applying configuration on the fly.

Example of a docker-compose.yml file:

version: '3.8' # File format version

services:
  web: # Service name
    image: nginx:latest # Used image
    ports:
      - "80:80" # Port forwarding
    volumes:
      - ./html:/usr/share/nginx/html # Volume mapping

  app: # Another service name
    build: . # Build image from Dockerfile in current directory
    ports:
      - "5000:5000"
    depends_on: # Dependency on another service
      - db

  db: # Database service name
    image: postgres:latest
    environment: # Environment variables
      POSTGRES_DB: mydatabase
      POSTGRES_USER: myuser
      POSTGRES_PASSWORD: mypassword

volumes: # Defined volumes
  data: # Named volume for data

Commands:

• docker-compose up: Starts containers.
• docker-compose down: Stops and removes containers.
• docker-compose build: Builds images.
• docker-compose ps: Shows the status of running containers.

Advantages:

• Simplifies management of complex multi-container applications.
• Ensures repeatability of deployment.
• Facilitates local development and testing.