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-posgresql-multiple-databases:/docker-entrypoint-initdb.d
    environment:
        - POSTGRES_MULTIPLE_DATABASES=db1,db2
        - 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,db2
        - POSTGRES_USER=myapp
        - POSTGRES_PASSWORD=