install upgrade tool kubeadm

apt install -y kubeadm
kubeadm config images list
k8s.gcr.io/kube-apiserver:v1.19.4
k8s.gcr.io/kube-controller-manager:v1.19.4
k8s.gcr.io/kube-scheduler:v1.19.4
k8s.gcr.io/kube-proxy:v1.19.4
k8s.gcr.io/pause:3.2
k8s.gcr.io/etcd:3.4.13-0
k8s.gcr.io/coredns:1.7.0

transfer gcr images to docker hub

open https://katacoda.com/courses/ubuntu/playground

go get github.com/xilu0/transfer
for im in `kubeadm config images list`;do  transfer --user=heishui --password="$repopass" --image=$im;done

upgrade kubernetes cluster

kubeadm upgrade plan
kubeadm upgrade apply v1.19.4

upgrade components

apt install -y kubectl kubelet