title: Issue with docker swarm and named volumes
body: <p>I'm having some issues using named volumes in one of my docker stacks.</p>
  
  <p>Basically I'm running a bitcoin node developed by bcoin. What I'm trying to achieve is to have the containers running the nodes to write and read the blockchain data from a Digital Ocean volume attached to one of my droplets (VMs). I'm guessing I'm having some issues because I normally use volumes one way only, having stuff in my host machine being present in my containers.</p>
  
  <p>This DO volume is present in the directory <code>/mnt/blockchain-data</code> in my manager node (or droplet).</p>
  
  <p>So here's my docker-stack.yml file:</p>
  
  <pre><code>version: "3.6"
  services:
    bcoin:
      image: hollarves/bcoin-mueve
      ports:
        #-- Mainnet
        # - "8333:8333"
        # - "8332:8332" # RPC/HTTP
        # - "8334:8334" # Wallet
        #-- Testnet
        - "18333:18333"
        - "18332:18332" # RPC/HTTP
        - "18334:18334"
      networks:
        - bitcoin-private-net
      volumes:
        - blockchain:/data
        - ${PWD}/bitcoin/secrets/bcoin.conf:/data/bcoin.conf
        - ${PWD}/bitcoin/secrets/wallet.conf:/data/wallet.conf
      environment:
        BCOIN_CONFIG: /data/bcoin.conf
      deploy:
        labels:
          - "traefik.docker.network=bitcoin-net"
          - "traefik.bcoin.frontend.rule=Host:bcoin.xxxx.com"
          - "traefik.bcoin.backend=bcoin"
          - "traefik.bcoin.port=18332"
          - "traefik.bcoin.frontend.entryPoints=http"
          - "traefik.bcoin-wallet.frontend.rule=Host:bcoin-wallet.xxxx.com"
          - "traefik.bcoin-wallet.backend=bcoin-wallet"
          - "traefik.bcoin-wallet.port=18334"
          - "traefik.bcoin-wallet.frontend.entryPoints=http"
        placement:
          constraints:
            - node.role == manager
  
  volumes:
    blockchain:
      driver: local
      driver_opts:
        type: bind
        device: :/mnt/blockchain-data
  
  networks:
    bitcoin-private-net:
      external: true
  </code></pre>
  
  <p>So basically I want whatever is in the <code>/data</code> directory of my containers to be synced with whatever it is in my <code>/mnt/blockchain-data</code> in my host machine. If the container writes some new blocks they should be copied to the <code>/mnt/blockchain-data</code> dir, and if a new bitcoin node is replicated, it should already have it's data directory synced with the files in my host machine. </p>
  
  <p>The main idea is to avoid redownloading the blockchain whenever a node is destroyed and recreated for whatever reason. As well as being able to replicate as many nodes I want without having to download the blockchain for each one of them.</p>
  
  <p>Any ideas on what I might be doing wrong?
  Thanks!</p>