title: Kubernetes kubectl access environment variables
body: <p>Does anyone know why this one doesn't (shows empty line):</p>
  
  <pre><code>kubectl exec kube -- echo $KUBERNETES_SERVICE_HOST
  </code></pre>
  
  <p>but this one works?</p>
  
  <pre><code>kubectl exec kube -- sh -c 'echo $KUBERNETES_SERVICE_HOST'
  </code></pre>