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Practical guide to Kubernetes Cluster Upgrade

In this guide I install Kuberentes version 1.17 and then upgrade it to the latest stable version(in time of writing 1.18).

Before begin

Provision Kubernetes 1.17.xx

First we need a Kubernets cluster. Choose one of following setup if you don't have your own:

When server nodes are up:

  • ssh to each node in case of HA cluster
  • re-install kubeadm, kubectl and kubelet with version tag 1.17.4-00 instead of mainstream. See below:
VERSION=1.17.4-00 
apt-get install --allow-change-held-packages -qy kubelet=$VERSION kubectl=$VERSION kubeadm=$VERSION
# All versions are avaialble at: 
# curl -s https://packages.cloud.google.com/apt/dists/kubernetes-xenial/main/binary-amd64/Packages | grep Version | awk '{print $2}'

Disable swap

  • Identify configured swap devices and files with cat /proc/swaps.
  • Turn off all swap devices and files with swapoff -a.
  • Remove any matching reference found in /etc/fstab.
  • Optional: Destroy any swap devices or files found in step 1 to prevent their reuse. Due to your concerns about leaking sensitive information, you may wish to consider performing some sort of secure wipe.

Backup etcd

Upgrade

Determine which version to upgrade

apt update
apt-cache madison kubeadm
# find the latest 1.18 version in the list
# it should look like 1.18.x-00, where x is the latest patch

Upgrading first control plane node

# replace x in 1.18.x-00 with the latest patch version
apt-mark unhold kubeadm && \
apt-get update && apt-get install -y kubeadm=1.18.x-00 && \
apt-mark hold kubeadm

# since apt-get version 1.1 you can also use the following method
apt-get update && \
apt-get install -y --allow-change-held-packages kubeadm=1.18.x-00
  • Verify kubeadm new version: kubeadm version
  • Drain the control plane node: kubectl drain <cp-node-name> --ignore-daemonsets
  • On control plane node run: sudo kubeadm upgrade plan
  • Choose a version to upgrade to: sudo kubeadm upgrade apply v1.18.x
  • Manually upgrade your CNI provider plugin.
  • Uncordon the control plane node: kubectl uncordon <cp-node-name>

Upgrade additional control plane nodes

  • Same as first CP node, but use: sudo kubeadm upgrade node, instead of sudo kubeadm upgrade apply

Upgrade kublet and kubectl

# replace x in 1.18.x-00 with the latest patch version
apt-mark unhold kubelet kubectl && \
apt-get update && apt-get install -y kubelet=1.18.x-00 kubectl=1.18.x-00 && \
apt-mark hold kubelet kubectl

# since apt-get version 1.1 you can also use the following method
apt-get update && \
apt-get install -y --allow-change-held-packages kubelet=1.18.x-00 kubectl=1.18.x-00
  • Restart kubelet: sudo systemctl restart kubelet

Upgrade worker nodes

Upgrade kubeadm on worker nodes

# replace x in 1.18.x-00 with the latest patch version
apt-mark unhold kubeadm && \
apt-get update && apt-get install -y kubeadm=1.18.x-00 && \
apt-mark hold kubeadm

# since apt-get version 1.1 you can also use the following method
apt-get update && \
apt-get install -y --allow-change-held-packages kubeadm=1.18.x-00

Drain the node

kubectl drain <node-to-drain> --ignore-daemonsets

Upgrade the kubelet configuration

sudo kubeadm upgrade node

Upgrade kubelet and kubectl

# replace x in 1.18.x-00 with the latest patch version
apt-mark unhold kubelet kubectl && \
apt-get update && apt-get install -y kubelet=1.18.x-00 kubectl=1.18.x-00 && \
apt-mark hold kubelet kubectl

# since apt-get version 1.1 you can also use the following method
apt-get update && \
apt-get install -y --allow-change-held-packages kubelet=1.18.x-00 kubectl=1.18.x-00
  • Restart the kubelet: sudo systemctl restart kubelet

Uncordon the node

kubectl uncordon <node-to-drain>

Verify status of the cluster

kubectl get nodes

More

Recovery from failure state