title: Add Docker Machine to Swarm cluster after creation
body: <p>A Docker Swarm cluster can be created as:</p>
  
  <pre><code>docker-machine create \
                 -d virtualbox --virtualbox-disk-size "5000" \
                 --swarm --swarm-master \
                 --swarm-discovery="consul://$(docker-machine ip consul-machine):8500" \
                 --engine-opt="cluster-store=consul://$(docker-machine ip consul-machine):8500" \
                 --engine-opt="cluster-advertise=eth1:2376" swarm-master
  docker-machine create \
                 -d virtualbox --virtualbox-disk-size "5000" \
                 --swarm \
                 --swarm-discovery="consul://$(docker-machine ip consul-machine):8500" \
                 --engine-opt="cluster-store=consul://$(docker-machine ip consul-machine):8500" \
                 --engine-opt="cluster-advertise=eth1:2376" swarm-node-01
  docker-machine create \
                 -d virtualbox --virtualbox-disk-size "5000" \
                 --swarm \
                 --swarm-discovery="consul://$(docker-machine ip consul-machine):8500" \
                 --engine-opt="cluster-store=consul://$(docker-machine ip consul-machine):8500" \
                 --engine-opt="cluster-advertise=eth1:2376" swarm-node-02
  </code></pre>
  
  <p>These machines join the Swarm cluster during creation itself. If a new Docker Machine is created as:</p>
  
  <pre><code>docker-machine create -d virtualbox --virtualbox-disk-size "5000" swarm-node-03
  </code></pre>
  
  <p>How can this machine be configured later to be part of the same Swarm cluster?</p>