Docker-compose works locally but not with docker-machine

Question

docker-compose.yml

db:
  image: mongo:3
  volumes:
    - ./mongo_data:/data/db

This works locally, with files being stored on the host at /data/db.

With docker-machine on macOS I get the following error:

db_1     | 2017-02-03T10:16:14.839+0000 I STORAGE  [initandlisten] exception in initAndListen: 20 Attempted to create a lock file on a read-only directory: /data/db, terminating

/data/db is on the mongo image, so I'm a bit confused as to why that would be different.

ETA: It's something to do with the volume mount.

Answer 1

It's the volume mount, for whatever reason.

I'll move on and find another method for backing up data.