Docker-compose: create named data volume

Form stackoverflow

To create a named data volume using the version 2 of compose files you will have a separated area:

version: '2'

services:
  db:
    image: postgres
    volumes:
      - amazingvolume:/var/lib/postgresql/data

volumes:
  amazingvolume:
    external: true

So you can define the volume name (amazingvolume), if it's external or not and under your service (db in this example) you can define which directory you gonna mount.