Image & Compose Volume Declarations

• 20 February 2025
• cursed,
• docker

If a Dockerfile specifies a VOLUME at a particular location:

VOLUME /my/cool/data/nested-data

And then in a docker compose file, you attempt to mount a parent directory:

services:
  my_service:
    image: docker/linux:latest
    volumes:
      - './data:/my/cool/data'

If you were intending to have the nested-data volume nested under the ./data directory, this will NOT do that. Instead, you will end up with a separate, dynamically created volume that will be in a different location. To actually map a local directory for the nested-data volume, you'll need to explicitly include that in the docker-compose service definition:

services:
  my_service:
    image: docker/linux:latest
    volumes:
      - './data:/my/cool/data'
      - './data/nested-data:/my/cool/data/nested-data'