docker-compose with multiple databases

Multiple databases in a single Docker container

The answers elsewhere on this page set up a dedicated container for each database, but a single MySQL server is capable of hosting multiple databases. Whether you should is a different question, but if you want multiple databases in a single container, here’s an example.

docker-compose.yml:

version: '3'

volumes:
  db:
    driver: local

services:
  db:
    image: mysql:5.7
    command: mysqld --character-set-server=utf8mb4 --collation-server=utf8mb4_unicode_ci
    volumes:
        - ./docker/provision/mysql/init:/docker-entrypoint-initdb.d
    environment:
      MYSQL_ROOT_PASSWORD: local

docker/provision/mysql/init/01-databases.sql:

# create databases
CREATE DATABASE IF NOT EXISTS `primary`;
CREATE DATABASE IF NOT EXISTS `secondary`;

# create root user and grant rights
CREATE USER 'root'@'localhost' IDENTIFIED BY 'local';
GRANT ALL PRIVILEGES ON *.* TO 'root'@'%';

How does this work?

This works because the MySQL Docker project has an entrypoint script that will run through all files in the /docker-entrypoint-initdb.d folder, if it exists. This is useful for setting up databases and initializing their schema and data. In docker-compose, we’re using volumes to map that virtual folder to a folder on the host system.