title: Deploying docker swarm without using docker machine
body: <p>Currently I have a bunch of <code>RHEL7 VMs</code> running on <code>RackSpace</code> and want to deploy docker swarm for testing purpose. The <code>Docker</code> Docs only describes the method to deploy docker swarm by using docker machine. </p>
  
  <p><strong>Question:</strong>
  Since <code>VirtualBox</code> cannot be used in VMs, are any other ways such that I can directly deploy docker swarm on my VMs without using docker machine?</p>