title: Docker compose named volume: find volume on host machine
body: <p>I have a docker-compose.yml:</p>
  
  <pre><code>version: '2'
  
  services:
     db:
       image: mysql:5.7
       volumes:
         - db_data:/var/lib/mysql
       restart: always
       environment:
         MYSQL_ROOT_PASSWORD: wordpress
         MYSQL_DATABASE: wordpress
         MYSQL_USER: wordpress
         MYSQL_PASSWORD: wordpress
  
     wordpress:
       depends_on:
         - db
       image: wordpress:latest
       ports:
         - "8000:80"
       restart: always
       environment:
         WORDPRESS_DB_HOST: db:3306
         WORDPRESS_DB_PASSWORD: wordpress
  volumes:
      db_data:
  </code></pre>
  
  <p>When I run this <code>docker-compose up -d</code> and then do <code>docker inspect -f '{{ (index .Mounts 0).Source }}' ef8be254a08b</code> for the running db container to get the Source which is specifying the volume location on the host, I always get "No such file or directory" if I <code>ls</code> the directory (<code>ls /var/lib/docker/volumes/test_db_data/_data: No such file or directory</code>).
  How is that possible to get the real location for the volume?</p>