1、停止服务删除原来的配置

  kubeadm reset -f
  rm -rf ~/.kube/
  rm -rf /etc/kubernetes/
  rm -rf /etc/systemd/system/kubelet.service.d
  rm -rf /etc/systemd/system/kubelet.service
  rm -rf /usr/bin/kube*
  yum clean all
  yum remove kube*

2、安装新版本的kubeadm

yum -y install kubeadm-1.20.0 kubectl-1.20.0 kubelet-1.20.0

systemctl enable kubelet.service

3、修改kubeadm-config.yaml

先生成配置yaml

kubeadm config print init-defaults > kubeadm-config.yaml

#修改ip为自己的机器ip
 advertiseAddress: 192.168.66.10
#这个是阿里云的镜像仓库,下载速度还可以
imageRepository: registry.cn-hangzhou.aliyuncs.com/google_containers

#使用ipvs模式

networking:
  dnsDomain: cluster.local
  podSubnet: "10.244.0.0/16"
  serviceSubnet: 10.96.0.0/12
scheduler: {}
---
apiVersion: kubeproxy.config.k8s.io/v1alpha1
kind: KubeProxyConfiguration
featureGates:
  SupportIPVSProxyMode: true
mode: ipvs

kubeadm config migrate --old-config kubeadm-config.yaml --new-config new.yaml

4、下载镜像

kubeadm config images pull --config /root/new.yaml

复制到其他机器上，去下载镜像

scp new.yaml root@k8s-node02:/root/

scp new.yaml root@k8s-node01:/root/

5、初始化master

 kubeadm init --config=kubeadm-config.yaml --upload-certs|tee kubeadm-init.log

Your Kubernetes control-plane has initialized successfully!

To start using your cluster, you need to run the following as a regular user:

  mkdir -p $HOME/.kube
  sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
  sudo chown $(id -u):$(id -g) $HOME/.kube/config

You should now deploy a pod network to the cluster.
Run "kubectl apply -f [podnetwork].yaml" with one of the options listed at:
  https://kubernetes.io/docs/concepts/cluster-administration/addons/

Then you can join any number of worker nodes by running the following on each as root:

kubeadm join 192.168.66.10:6443 --token abcdef.0123456789abcdef \
    --discovery-token-ca-cert-hash sha256:b7a43fd7651c783f87dfcfda5a2ccc61317e7ee28624f9324f4caeca525d8685 

说明我们升级成功了，剩下的就是把node加入到集群即可

6、加入集群后，node的状态不正常是网络原因，需要执行下原来的flannel的安装yaml即可

 kubectl apply -f kube-flannel.yml 

7、如果kubectl  get nodes 报错“The connection to the server localhost:8080 was refused - did you specify the right host or port?”

我们可以加一个环境变量即可

 echo "export KUBECONFIG=/etc/kubernetes/admin.conf" >> /etc/profile