title: The extention of updateable fields in Pod
body: <p>I wonder why only some fields of a pod can be modified。
  The updateable fields are：</p>
  <ol>
  <li>spec.containers[*].image</li>
  <li>spec.initContainers[*].image</li>
  <li>spec.activeDeadlineSeconds
  <a href="https://i.stack.imgur.com/QN85j.png" rel="nofollow noreferrer">1</a></li>
  </ol>
  <p>In my actual business, I have a need to change the schedulername of a pod.
  So i change the validating codes in the file of validation.go. And i created a second scheduler named kube-scheduler-test.
  <a href="https://i.stack.imgur.com/TMLuL.png" rel="nofollow noreferrer">That is pod whose schedulername is kube-scheduler-test</a>
  When i created a new pod whose schedulername is kube-scheduler-test, then the kube-scheduler-test will update the schedulername of pod to default-scheduler.
  And then default-scheduler will schedule this pod to specified node.</p>
  <p><img src="https://i.stack.imgur.com/TYuCy.png" alt="enter image description here" /></p>
  <p><img src="https://i.stack.imgur.com/GmRaC.png" alt="enter image description here" /></p>
  <p>Could you explain why only some fields of a pod can be modified and whether my method of changing the schedulername acceptable or not？</p>