Upgrading kubeadm HA clusters from v1.12 to v1.13

This page explains how to upgrade a highly available (HA) Kubernetes cluster created with kubeadm from version 1.12.x to version 1.13.y. In addition to upgrading, you must also follow the instructions in Creating HA clusters with kubeadm.

Before you begin
Prepare for both methods
Stacked control plane nodes
External etcd
Next steps
If something goes wrong

Before you begin

Before proceeding:

You need to have a kubeadm HA cluster running version 1.12 or higher.
Make sure you read the release notes carefully.
Make sure to back up any important components, such as app-level state stored in a database. kubeadm upgrade does not touch your workloads, only components internal to Kubernetes, but backups are always a best practice.
Check the prerequisites for Upgrading/downgrading kubeadm clusters between v1.12 to v1.13.

Note: All commands on any control plane or etcd node should be run as root.

Prepare for both methods

Upgrade kubeadm to the version that matches the version of Kubernetes that you are upgrading to:

apt-mark unhold kubeadm && \
apt-get update && apt-get upgrade -y kubeadm && \
apt-mark hold kubeadm

Check prerequisites and determine the upgrade versions:

kubeadm upgrade plan

You should see something like the following:

Upgrade to the latest version in the v1.13 series:

COMPONENT            CURRENT   AVAILABLE
API Server           v1.12.2   v1.13.0
Controller Manager   v1.12.2   v1.13.0
Scheduler            v1.12.2   v1.13.0
Kube Proxy           v1.12.2   v1.13.0
CoreDNS              1.2.2     1.2.6

Stacked control plane nodes

Upgrade the first control plane node

Modify configmap/kubeadm-config for this control plane node:

kubectl edit configmap -n kube-system kubeadm-config

Make the following modifications to the ClusterConfiguration key:

etcd

Remove the etcd section completely

Make the following modifications to the ClusterStatus key:

apiEndpoints

Add an entry for each of the additional control plane hosts

Start the upgrade:

kubeadm upgrade apply v<YOUR-CHOSEN-VERSION-HERE>

You should see something like the following:

[upgrade/successful] SUCCESS! Your cluster was upgraded to "v1.13.0". Enjoy!

The kubeadm-config ConfigMap is now updated from v1alpha3 version to v1beta1.

Upgrading additional control plane nodes

Start the upgrade:

kubeadm upgrade node experimental-control-plane

External etcd

Upgrade the first control plane

Run the upgrade:

kubeadm upgrade apply v1.13.0

Upgrade the other control plane nodes

For other control plane nodes in the cluster, run the following command:

kubeadm upgrade node experimental-control-plane

Next steps

Manually upgrade your CNI provider

Your Container Network Interface (CNI) provider might have its own upgrade instructions to follow. Check the addons page to find your CNI provider and see whether you need to take additional upgrade steps.

Update kubelet and kubectl packages

Upgrade the kubelet and kubectl by running the following on each node:

# use your distro's package manager, e.g. 'apt-get' on Debian-based systems
# for the versions stick to kubeadm's output (see above)
apt-mark unhold kubelet kubectl && \
apt-get update && \
apt-get install kubelet=<NEW-K8S-VERSION> kubectl=<NEW-K8S-VERSION> && \
apt-mark hold kubelet kubectl && \
systemctl restart kubelet

In this example a deb-based system is assumed and apt-get is used for installing the upgraded software. On rpm-based systems the command is yum install <PACKAGE>=<NEW-K8S-VERSION> for all packages.

Verify that the new version of the kubelet is running:

systemctl status kubelet

Verify that the upgraded node is available again by running the following command from wherever you run kubectl:

kubectl get nodes

If the STATUS column shows Ready for the upgraded host, you can continue. You might need to repeat the command until the node shows Ready.

If something goes wrong

If the upgrade fails, see whether one of the following scenarios applies:

If kubeadm upgrade apply failed to upgrade the cluster, it will try to perform a rollback. If this is the case on the first master, the cluster is probably still intact.

You can run kubeadm upgrade apply again, because it is idempotent and should eventually make sure the actual state is the desired state you are declaring. You can run kubeadm upgrade apply to change a running cluster with x.x.x --> x.x.x with --force to recover from a bad state.

If kubeadm upgrade apply on one of the secondary masters failed, the cluster is upgraded and working, but the secondary masters are in an undefined state. You need to investigate further and join the secondaries manually.

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