alias k=kubectl

kubectl get nodes

kubectl describe node | grep Taints

# how many applications are hosted on the cluster
kubectl get deploy 

# what is the latest stable version available for upgrade
kubeadm upgrade plan

# drain the master node of workloads 
k drain controlplane --ignore-daemonsets

# upgrade the controlplane components to exact version v1.20.0

# version check
cat /etc/*release*
NAME=Ubuntu

apt update
apt-cache madison kubeadm

apt-get --version
apt-get install -y --allow-change-held-packages kubeadm=1.20.0-00

kubeadm version

kubeadm upgrade plan

sudo kubeadm upgrade apply v1.20.0
apt-get update && \\
apt-get install -y --allow-change-held-packages kubelet=1.20.x-00 kubectl=1.20.x-00

• restart the kubelet

sudo systemctl daemon-reload
sudo systemctl restart kubelet

k get nodes

k uncordon controlplane

k drain node01
k get node
k get pods -o wide

# upgrade the worker node to the exact version v1.20.0

k get nodes -o  wide

ssh 10.38.209.12

apt update
apt-cache madison kubeadm

apt-get --version
apt-get install -y --allow-change-held-packages kubeadm=1.20.x-00
sudo kubeadm upgrade node

apt-get update && \\
apt-get install -y --allow-change-held-packages kubelet=1.20.0-00 kubectl-1.20.0-00

sudo  systemctl daemon-reload
sudo systemctl restart kubelet

exit

k get nodes

k uncordon node01

On the controlplane node, run the command run the following commands:

apt update
This will update the package lists from the software repository.

apt install kubeadm=1.20.0-00
This will install the kubeadm version 1.20

kubeadm upgrade apply v1.20.0
This will upgrade kubernetes controlplane. Note that this can take a few minutes.

apt install kubelet=1.20.0-00 
#This will update the kubelet with the version 1.20.

You may need to restart kubelet after it has been upgraded.
Run: systemctl restart kubelet