title: Upgrade kubernetes from v1.11 to v1.15
body: <p>My source k8s cluster version is v1.11.5 and the dest k8s cluster version is v1.15.2 with in-place upgrade.</p>
  
  <p>K8S Cluster Status.Three master nodes with k8s controll plane:</p>
  
  <pre><code>NAME   STATUS   ROLES    AGE   VERSION
  a1     Ready    master   23h   v1.11.5
  a2     Ready    master   23h   v1.11.5
  a3     Ready    master   22h   v1.11.5
  </code></pre>
  
  <p>I didn't use kubeadm upgrade because the enforced k8s skew policies.I followed the steps below:</p>
  
  <p>[step 0] kubectl drain node a3 and remove all k8s components on a3.</p>
  
  <p>[step 1] use kubeadm init to install v1.15.2 k8s on node a3 and undrain node a3.</p>
  
  <p>[step 2] redo the steps above on node a2 and a1.</p>
  
  <p>After installed v1.15.2 k8s on each node,K8S Cluster Status becomes:</p>
  
  <pre><code>NAME   STATUS   ROLES    AGE   VERSION
  a1     Ready    master   23h   v1.15.2
  a2     Ready    master   23h   v1.15.2
  a3     Ready    master   22h   v1.15.2
  </code></pre>
  
  <p><strong>So my question is is there any problem on this upgrade solution?</strong></p>
  
  <p>Because the k8s version skew policy says k8s does not support upgrading on cross y version.For example,I have to upgrade k8s from v1.11 to v1.12 and then from v1.12 to v1.13.</p>