title: Declarative way of specifying units that should run on a CoreOS cluster?
body: <p>Is there a declarative way of specifying what units should be running on a CoreOS cluster and to apply that to an existing CoreOS cluster?  It is undesirable to have to run manual fleetctl commands each time the unit setup changes.</p>
  
  <p>It would be similar to how Ansible makes it possible to declaratively specify what packages should be installed in an server and then apply that to an existing server.</p>