报错信息：
[root@vm ~]# sudo yum install -y kubelet-1.20.9 kubeadm-1.20.9 kubectl-1.20.9 --disableexcludes=kubernetes
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
- epel: mirror-icn.yuki.net.uk
No package kubelet-1.20.9 available.
No package kubeadm-1.20.9 available.
No package kubectl-1.20.9 available.
Error: Nothing to do
解决：
1.修改/etc/yum.repos.d/kubernetes.repo
[kubernetes]
name=Kubernetes
baseurl=https://packages.cloud.google.com/yum/repos/kubernetes-el7-$basearch
enabled=1
gpgcheck=1
gpgkey=https://packages.cloud.google.com/yum/doc/yum-key.gpg https://packages.cloud.google.com/yum/doc/rpm-package-key.gpg
2.重新加载云源
yum clean all && yum makecache
3.再次安装
sudo yum install -y kubelet-1.20.9 kubeadm-1.20.9 kubectl-1.20.9 --disableexcludes=kubernetes