kubeadm管理证书之续签证书
可用于检查证书过期时间：
kubeadm alpha certs check-expiration
kubeadm alpha certs 命令详解：
Available Commands:
certificate-key 生成证书和key
check-expiration 检测证书过期时间
renew 续订Kubernetes集群的证书
kubeadm alpha certs命令仅支持v1.15及其以上的版本。
手动续订apiserver的证书-apiserver.crt
[root@master-63 ~]# kubeadm alpha certs check-expiration
[check-expiration] Reading configuration from the cluster...
[check-expiration] FYI: You can look at this config file with 'kubectl -n kube-system get cm kubeadm-config -oyaml'
CERTIFICATE EXPIRES RESIDUAL TIME CERTIFICATE AUTHORITY EXTERNALLY MANAGED
admin.conf May 22, 2021 15:26 UTC 327d no
apiserver May 22, 2021 15:26 UTC 327d ca no
apiserver-etcd-client May 22, 2021 15:26 UTC 327d etcd-ca no
apiserver-kubelet-client May 22, 2021 15:26 UTC 327d ca no
controller-manager.conf May 22, 2021 15:26 UTC 327d no
etcd-healthcheck-client May 22, 2021 15:26 UTC 327d etcd-ca no
etcd-peer May 22, 2021 15:26 UTC 327d etcd-ca no
etcd-server May 22, 2021 15:26 UTC 327d etcd-ca no
front-proxy-client May 22, 2021 15:26 UTC 327d front-proxy-ca no
scheduler.conf May 22, 2021 15:26 UTC 327d no
CERTIFICATE AUTHORITY EXPIRES RESIDUAL TIME EXTERNALLY MANAGED
ca May 20, 2030 15:26 UTC 9y no
etcd-ca May 20, 2030 15:26 UTC 9y no
front-proxy-ca May 20, 2030 15:26 UTC 9y no
当前 apiserver.crt 到期时间是 May 22, 2021 15:26 UTC 剩余327天
执行renew更新：
[root@master-63 ~]# kubeadm alpha certs renew apiserver
[renew] Reading configuration from the cluster...
[renew] FYI: You can look at this config file with 'kubectl -n kube-system get cm kubeadm-config -oyaml'
certificate for serving the Kubernetes API renewed
重启kubelet会自动重新创建核心组件
systemctl restart kubelet
验证：
apiserver证书到期时间发生了变化， 不过不是顺延一年， 而是 从你 执行renew成功的时间开始续签一年。
如果要将所有证书续签一年，则执行：
#kubeadm alpha certs renew all
[root@master-63 ~]# kubeadm alpha certs renew all
[renew] Reading configuration from the cluster...
[renew] FYI: You can look at this config file with 'kubectl -n kube-system get cm kubeadm-config -oyaml'
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
查看全部估清了
以上结束了.
使用外部CA续订证书
1.生成CSR和私钥：
kubeadm alpha certs renew apiserver --csr-only --csr-dir /tmp/apiserver.csr
--csr-only：仅生成CSR。
--csr-dir：生成的CSR和私钥文件保存在哪里，默认保存在/etc/kubernetes/pki
2.查看CSR和私钥：
命令输出结果中提供了CSR和私钥。
root@k8s-master:~# ls /tmp/apiserver.csr/
apiserver.csr apiserver.key
- 使用该私钥到CA上请求签发证书。
将颁发的证书及私钥复制到PKI目录/etc/kubernetes/pki中。
参考链接
https://kubernetes.io/zh/docs/reference/setup-tools/kubeadm/kubeadm-alpha/