Database Setup with Docker

1- Creating multiple databases in the same Container:

When a PostgreSQL container is started for the first time, all .sql and .sh files located in /docker-entrypoint-initdb.d are automatically executed.

How to use it:

Create a .sql file (or use "docker_postgres_init.sql") containing the databases needed, ex:

CREATE DATABASE db_init;
CREATE DATABASE sensor_test;

Then mount the file in compose.yml (Note: the docker_postgres_init.sql file is already mounted, so using it is easier.) as such:

postgres: 
    volumes:
         - ./docker_postgres_init.sql:/docker-entrypoint-initdb.d/docker_postgres_init.sql

Important notes:

• The default database defined by POSTGRES_DB: sensors will still be created automatically.
• Init scripts only run on first container initialization. If new databases are added later, make sure to reset the volume. In the terminal, type the following in the same order:

docker compose down -v
docker compose up --build

• All databases in the same container will share the same PostgreSQL instance, use the same user and password, and use the same port.

Creating separate containers for each database

Another approach is to create a separate PostgreSQL container for each database by adding additional services in compose.yml.

To use

Add another service using the postgres image as such:

postgres_test:
    image: postgres
    container_name: PostgreSQL
    #ports:  
        - "5432:5432" 
    environment:
      POSTGRES_DB: sensors_test
      POSTGRES_PASSWORD: someOtherPasword123
    networks:
      - DTnet
    restart: unless-stopped
    volumes:
      - pgdata_test:/var/lib/postgresql

Considerations

• Each container must have a unique container name, port mapping, and its own volume.
• You can configure different database names, different users/passwords, and separate storage.