title: How to clean-up old unused Kubernetes images/tags?
body: <p>To simplify <strong>deployment</strong> and short term roll-back, it's useful to use a new Docker image tag for each new version to deploy on <strong>Kubernetes</strong>. Without clean-up this means that old images:tags are kept forever.</p>
  
  <p>How can I <strong>list all image:tag that are used by a Kubernetes container</strong> so that I can find all old image:tag that are old and not used to delete them automatically from the <strong>Docker Registry</strong>?</p>
  
  <p>My goal is ideally for <em>Google Container Engine</em> (GKE) to delete unused images a <em>Google Container Registry</em>.</p>