disaster !!! I have taken up upgrade lecture and how it is going. long story short. as per plan i upgraded kubeadm from version 1.19.0 to 1.21.1 which was available for upgrade. and now I am unable to continue upgrading other components using kubeadm upgrade apply. looks like i messed up in speicfiying the exact version i want to upgrade to for kubeadm. it should be 1.20 instead of 1.21 but still it should support 3 levels down isn’t it?
Kubeadm is different software but its should exactly match the cluster version for smooth processing.
2 level down version mapping is for kubelet and kube-proxy in comparison to kube-apiservier version
You can use apt pkg manager to downgrade as well.