Using multiple databases with the official PostgreSQL Docker image

The official recommendation for creating multiple databases is as follows:

If you would like to do additional initialization in an image derived from this one, add one or more *.sql, *.sql.gz, or *.sh scripts under /docker-entrypoint-initdb.d (creating the directory if necessary). After the entrypoint calls initdb to create the default postgres user and database, it will run any *.sql files and source any *.sh scripts found in that directory to do further initialization before starting the service.

This directory contains a script to create multiple databases using that mechanism.

Usage

By mounting a volume

Clone the repository, mount its directory as a volume into /docker-entrypoint-initdb.d and declare database names separated by commas in POSTGRES_MULTIPLE_DATABASES environment variable as follows (docker-compose syntax):

myapp-postgresql:
    image: postgres:9.6.2
    volumes:
        - ../docker-postgresql-multiple-databases:/docker-entrypoint-initdb.d
    environment:
        - POSTGRES_MULTIPLE_DATABASES: db1:pwdb1,db2:pwddb2
        - POSTGRES_USER: myapp
        - POSTGRES_PASSWORD:

By building a custom image

Clone the repository, build and push the image to your Docker repository, for example for Google Private Repository do the following:

docker build --tag=eu.gcr.io/your-project/postgres-multi-db .
gcloud docker -- push eu.gcr.io/your-project/postgres-multi-db

You still need to pass the POSTGRES_MULTIPLE_DATABASES environment variable to the container:

myapp-postgresql:
    image: eu.gcr.io/your-project/postgres-multi-db
    environment:
        - POSTGRES_MULTIPLE_DATABASES: db1:pwdb1,db2:pwddb2
        - POSTGRES_USER: myapp
        - POSTGRES_PASSWORD:

Non-standard database names

If you need to use non-standard database names (hyphens, uppercase letters etc), quote them in POSTGRES_MULTIPLE_DATABASES:

    environment:
        - POSTGRES_MULTIPLE_DATABASES: "test-db-1":"test-db-pw-1","test-db-2":"test-db-pw-2"

Add to docker composer as a service

You can pass the POSTGRES_MULTIPLE_DATABASES environment variable to the docker composer like this:

postgres:
    image: postgres
    container_name: postgres
    restart: unless-stopped
    environment:
      POSTGRES_PASSWORD: your!!!Password
      POSTGRES_MULTIPLE_DATABASES: db1:db1@Password, db2:db2@Password, db3:db3@Password
    ports:
      - "5432:5432"
    healthcheck:
      test: ["CMD-SHELL", "pg_isready -U postgres"]
      interval: 5s
      timeout: 5s
      retries: 5
    volumes:
      - ./<path-of-the-entrypoint>/multiple-databases.sh:/docker-entrypoint-initdb.d/multiple-databases.sh