Container reinit database on rebuild

[kpeter477]

I have the following docker-compose script which resets the whole database server to initial state when I run docker-compose build:

postgres:
    image: postgres:12
    mem_limit: 2048M
    mem_reservation: 300M
    environment:
      POSTGRES_PASSWORD: abcd
    restart: unless-stopped
    volumes:
      - /data/erp/db:/var/lib/postgresql
    networks:
      - app_net
    ports:
      - 5432:5432

How can I avoid this? Nothing is removing content on the host.

[yosifkit]

You need to change the volume to /var/lib/postgresql/data, otherwise your volume isn't saving anything but an empty folder. (The image already has a VOLUME defined at /var/lib/postgresql/data so an anonymous volume is created there if one is not defined; usually docker-compose tries hard to reuse any anonymous volumes, so it works most of the time.)