Docker Compose with shell environment variable error

Question

I'm running a Docker deployment for an application. I'm mounting a volume where I want the external path to be provided by a shell environment variable. I get this error:

ERROR: for video-server Cannot create container for service video-server: invalid volume specification: '46b9d2fb3b9b13c9404d31bae571dac3f633122393c4a77f2561afb8aed5c06e:=/opt/videos:rw': invalid mount config for type "volume": invalid mount path: '=/opt/videos' mount path must be absolute

My docker-compose configuration is this:

video-server:
    build:
      context: .
      dockerfile: video-server_Dockerfile
    container_name: video-server
    networks:
      - videoManagerNetwork
    environment:
      - VIDEO_MANAGER_DIR=/opt/videos
    volumes:
      - ${VIDEO_MANAGER_DIR_PROD}=/opt/videos
    ports:
      - 9000:8080

I can see the correct value of the VIDEO_MANAGER_DIR_PROD environment variable by doing both of these commands, so I know it's on my shell:

echo $VIDEO_MANAGER_DIR_PROD
sudo echo $VIDEO_MANAGER_DIR_PROD

What's strange is that, if I do a complete wipe of my docker configurations (sudo docker system prune --all --volumes), and then run the docker-compose for the first time (sudo docker-compose up -d), everything works.

However, if I take the container down, rebuild it, and try to run that same command (sudo docker-compose up -d) again, then I get the error displayed above.

Answer 1

You cannot assign the source volume like a variable, so you will use : for this assignment.

Documentation about Docker Compose volumes: docs.docker.com

video-server:
  build:
    context: .
    dockerfile: video-server_Dockerfile
  container_name: video-server
    networks:
      - videoManagerNetwork
    environment:
      - VIDEO_MANAGER_DIR: /opt/videos
    volumes:
      - ${VIDEO_MANAGER_DIR_PROD}:/opt/videos
    ports:
      - 9000:8080