现象：

 kubectl get nodes执行报错：

kubectl  get nodes
Unable to connect to the server: x509: certificate signed by unknown authority (possibly because of "crypto/rsa: verification error" while trying to verify candidate authority certificate "kubernetes")

问题：

/root/.kube/config证书认证错误，使用正确证书，可能是kubeadm reset证书未删除

解决办法

删除原来的证书及缓存文件

#rm -rf  /root/.kube/*

拷贝master节点上证书到目录即可