initdb: could not change permissions of directory

Question

I am new to the docker ecosystem and I am trying to spin up a simple postgres container along with a volume so it persists its data, by using a yaml composer file. The file is as follows:

# Use postgres/example user/password credentials
version: '3.3'
services:
    db:
        image: postgres
        environment:
            POSTGRES_DB: recrow
            POSTGRES_USER: recrow
            POSTGRES_PASSWORD: recrow_db_1000
            PGDATA: /var/lib/pgsql/data/pgdata
        volumes:
          - ./pgsql/data:/var/lib/pgsql/data/pgdata

However, upon calling docker-compose -f stack.yml up I get the following error:

fixing permissions on existing directory /var/lib/postgresql/data/pgdata ... initdb: could not change permissions of directory "/var/lib/postgresql/data/pgdata": Operation not permitted

/var/lib/pgsql/data/pgdata is supposed to be a directory relative to the container's root, while ./pgsql/data is a path on the host. I am running the container from an ntfs-3g partition mounted on /mnt/storage. What could be the problem? I am also running docker without root permissions, by adding my user to the docker group and this user also has full access to the beforementioned mount point /mnt/storage.

Answer 1

I'm guessing this is going to be an incompatibility with ntfs-3g. The PostgreSQL image contains an entrypoint script that is doing some permission changes on container start: https://github.com/docker-library/postgres/blob/972294a377463156c8d61297320c872fc7d370a9/9.6/docker-entrypoint.sh#L32-L38. I found another relevant question at https://askubuntu.com/questions/11840/how-do-i-use-chmod-on-an-ntfs-or-fat32-partition that talks about being able to set permissions at mount time. But not being able to change via chmod or chown (which is likely the reason for the failure in this case).

Unfortunately, I think the answer here is that you cannot use ntfs-3g safely for backing Docker host volume mounts.