From 24edeac0b49ae32c95282ac6e15183e18e01bcac Mon Sep 17 00:00:00 2001
From: Marc Bihlmaier <30314040+rdxmb@users.noreply.github.com>
Date: Mon, 4 Nov 2019 23:12:12 +0100
Subject: [PATCH] Update kubeadm-upgrade.md (#17407)

Sometimes, pods like `coredns` only run on the master nodes. If there is a problem with upgrading the master node (e.g. if it is interrupted) those pods will not keep running - and other pods will have problems with connections.

Draining the master node will switch those pods to other nodes before the upgrade-process.
---
 .../administer-cluster/kubeadm/kubeadm-upgrade.md    | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/content/en/docs/tasks/administer-cluster/kubeadm/kubeadm-upgrade.md b/content/en/docs/tasks/administer-cluster/kubeadm/kubeadm-upgrade.md
index 2ca6f9ddce..43cb73a31d 100644
--- a/content/en/docs/tasks/administer-cluster/kubeadm/kubeadm-upgrade.md
+++ b/content/en/docs/tasks/administer-cluster/kubeadm/kubeadm-upgrade.md
@@ -88,6 +88,12 @@ The upgrade workflow at high level is the following:
     kubeadm version
     ```
 
+1.  Drain the control plane node:
+
+    ```shell
+    kubectl drain $MASTER --ignore-daemonsets
+    ```
+
 1.  On the control plane node, run:
 
     ```shell
@@ -231,6 +237,12 @@ The upgrade workflow at high level is the following:
 
     This step is not required on additional control plane nodes if the CNI provider runs as a DaemonSet.
 
+1.  Uncordon the control plane node
+
+    ```shell
+    kubectl uncordon $MASTER
+    ```
+
 ### Upgrade additional control plane nodes
 
 1.  Same as the first control plane node but use: