手动更新证书
由 kubeadm 生成的客户端证书默认只有一年有效期，我们可以通过 check-expiration 命令来检查证书是否过期：
kubeadm alpha certs check-expiration
备份原来的证书
mkdir /etc/kubernetes.bak
cp -r /etc/kubernetes/pki/ /etc/kubernetes.bak
cp /etc/kubernetes/*.conf /etc/kubernetes.bak
备份 etcd 数据目录：
cp -r /var/lib/etcd /var/lib/etcd.bak
接下来执行更新证书的命令：
kubeadm alpha certs renew all --config=kubeadm.yaml
kubeadm alpha certs renew all --config=kubeadm.yaml
certificate embedded in the kubeconfig file for the admin to use and for kubeadm itself renewed
certificate for serving the Kubernetes API renewed
certificate the apiserver uses to access etcd renewed
certificate for the API server to connect to kubelet renewed
certificate embedded in the kubeconfig file for the controller manager to use renewed
certificate for liveness probes to healthcheck etcd renewed
certificate for etcd nodes to communicate with each other renewed
certificate for serving etcd renewed
certificate for the front proxy client renewed
certificate embedded in the kubeconfig file for the scheduler manager to use renewed
通过上面的命令证书就一键更新完成了，这个时候查看上面的证书可以看到过期时间已经是一年后的时间了：
kubeadm alpha certs check-expiration
然后记得更新下 kubeconfig 文件：
kubeadm init phase kubeconfig all --config kubeadm.yaml
[kubeconfig] Using kubeconfig folder "/etc/kubernetes"
[kubeconfig] Using existing kubeconfig file: "/etc/kubernetes/admin.conf"
[kubeconfig] Using existing kubeconfig file: "/etc/kubernetes/kubelet.conf"
[kubeconfig] Using existing kubeconfig file: "/etc/kubernetes/controller-manager.conf"
[kubeconfig] Using existing kubeconfig file: "/etc/kubernetes/scheduler.conf"
将新生成的 admin 配置文件覆盖掉原本的 admin 文件:
mv $HOME/.kube/config $HOME/.kube/config.old
cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
chown $(id -u):$(id -g) $HOME/.kube/config
在三台Master上执行重启kube-apiserver、kube-controller、kube-scheduler、etcd这4个容器，以便使证书生效。
docker ps |grep -E 'k8s_kube-apiserver|k8s_kube-controller-manager|k8s_kube-scheduler|k8s_etcd_etcd' | awk -F ' ' '{print $1}' |xargs docker restart