Get IP addresses of interfaces in Docker containers

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Docker containers can be binded to multiple interfaces

Each interfaces comes with a dynamic IP address.

Think about following scenario:

  • In your Docker compose file you specified your DB and Web service.

  • You bind DB to internal network interface.

  • You bind your web service to both your internal network interface and external interface.

  • You want your Web service only bind to external interface.

  • How do you do that?

Sample Docker compose file:

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version: '3.1'
services:
  web:
    image: web-service:latest
    container_name: web-service
    restart: unless-stopped
    depends_on:
      - db
    networks:
      - external
      - internal
    volumes:
      - /data:/data:Z
    environment:
      database_client: mysql
      database_connection_host: db
      database_connection_port: 3306
      database_connection_user: web
      database_connection_password: web
      database_connection_database: web
      server_port: 443
      server_host: 0.0.0.0
  db:
    image: mariadb:bionic
    container_name: mariaDB
    restart: unless-stopped
    environment:
      MYSQL_RANDOM_ROOT_PASSWORD: "true"
      MYSQL_USER: web
      MYSQL_PASSWORD: web
      MYSQL_DATABASE: web
    networks:
      - internal
    volumes:
      - /mariaDB:/var/lib/mysql:Z
networks:
  external:
    external: true
  internal:
    driver: bridge

What should be put in server_host if I don’t like 0.0.0.0?

Would be interesting to investigate.

Answer:

One may simply bind the web server to “external” network by looking up the available links using something similar to ip addr.
Meanwhile it is possible to assign static IP to a container.