$ docker run -d --name postgres --network some-network -e POSTGRES_PASSWORD=secret -e POSTGRES_USER=redmine postgres

$ docker run -d --name mysql --network some-network -e MYSQL_USER=redmine -e MYSQL_PASSWORD=secret -e MYSQL_DATABASE=redmine -e MYSQL_RANDOM_ROOT_PASSWORD=1 mysql:5.7

docker run -d --name redmine /
--network redmine-network /
-e REDMINE_DB_POSTGRES=postgres /
-e REDMINE_DB_USERNAME=redmine /
-e REDMINE_DB_PASSWORD=secret /
redmine

version: '3.1'

services:

  redmine:
    image: redmine
    restart: always
    ports:
      - 8080:3000
    environment:
      REDMINE_DB_MYSQL: db
      REDMINE_DB_PASSWORD: example

  db:
    image: mysql:5.7
    restart: always
    environment:
      MYSQL_ROOT_PASSWORD: example
      MYSQL_DATABASE: redmine

version: '3.1'

services:

  redmine:
    image: redmine
    restart: always
    ports:
      - 8080:3000
    environment:
      REDMINE_DB_POSTGRES: postgres
      REDMINE_DB_USERNAME: redmine
      REDMINE_DB_PASSWORD: secret

  db:
    image: postgres
    restart: always
    environment:
      POSTGRES_USER: example
      POSTGRES_PASSWORD: redmine

$ docker run -d --name redmine /
-v /my/own/datadir:/usr/src/redmine/files /
--link postgres:postgres /
redmine