upgrade

#Upgrading the Kubernetes Cluster

Login to Controller VM from Launcher VM and get the version of the API server:
kubectl version --short

Release the hold on versions of kubeadm and kubelet:
sudo apt-mark unhold kubeadm kubelet

Install version 1.18.8.0 of kubeadm:
sudo apt install -y kubeadm=1.18.8-00

Hold the version of kubeadm at 1.18.8:
sudo apt-mark hold kubeadm

Verify the version of kubeadm:
kubeadm version

Plan the upgrade of all the controller components:
sudo kubeadm upgrade plan

Upgrade the controller components:
sudo kubeadm upgrade apply v1.18.8

Release the hold on the version of kubectl:
sudo apt-mark unhold kubectl

Upgrade kubectl:
sudo apt install -y kubectl=1.18.8-00

Hold the version of kubectl at 1.18.8:
sudo apt-mark hold kubectl

Upgrade the version of kubelet:
sudo apt install -y kubelet=1.18.8-00

Hold the version of kubelet at 1.18.8:
sudo apt-mark hold kubelet

Login to worker0 VM and release hold on kubelet version:
sudo apt-mark unhold kubelet

Upgrade the version of kubelet:
sudo apt install -y kubelet=1.18.8-00

Hold the version of kubelet at 1.18.8:
sudo apt-mark hold kubelet

Login to worker1 VM and release hold on kubelet version:
sudo apt-mark unhold kubelet

Upgrade the version of kubelet:
sudo apt install -y kubelet=1.18.8-00

Hold the version of kubelet at 1.18.8:
sudo apt-mark hold kubelet

Login to Controller VM and check whether all nodes are upgraded
kubectl get nodes