Docker Volume with specified path not populated from image

Question

My docker image contain files in directory /data

When I run docker container with named or unnamed volume associated with this directory volume is populated with files from image (as it sould be).

But when I try to put volume to specific path like:

volumes:
  - ./data:/data

Host directory ./data is not populated witch files from image it is empty. (but accessible from container).

Is there some difference between creation of named, unnamed volumes and volumes in specific host path that explains this behavior?

My dockrefile:

FROM hypriot/rpi-alpine 

RUN apk update && \
    apk upgrade && \
    apk add --no-cache bash minidlna && \
    rm -rf /var/cache/apk/*

RUN mkdir /data %% \
    mkdir /data/log && \
    mkdir /data/db

COPY minidlna.conf /data/minidlna.conf
COPY minidlna.conf /minidlna.conf
COPY entrypoint.sh /entrypoint.sh

VOLUME ["/data"]

RUN chmod +x /entrypoint.sh
ENTRYPOINT ["/entrypoint.sh"]

and docker-compose.yml

version: "3" 

services:
  minidlna:
    image: silvan85/rpi-minidlna
    volumes:
      - ./data:/data
      - /media/ExternalHDD/media:/media
    network_mode: "host"
    restart: unless-stopped

Answer 1

When you mount a host directory into container, the contents of host directory shadow the contents of container.

Please see mount files present in a directory in docker image with the directory in the host