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,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=

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-2"

The create-multiple-postgresql-full.sh and docker-compose.yml shows an example of how to create both databases and users exclusively to them and assign passwords to them. user1 will not have access to db1,db2.