k8s 证书过期处理

问题

kubeadm 安装的集群默认签发的证书有效期为1年，到期后集群组件之间无法正常通信。控制面组件日志会有报错信息。

证书修复流程

1. 检查当前证书状态

$ kubeadm 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 -o yaml'
[check-expiration] Error reading configuration from the Cluster. Falling back to default configuration

CERTIFICATE                EXPIRES                  RESIDUAL TIME   CERTIFICATE AUTHORITY   EXTERNALLY MANAGED
admin.conf                 Feb 16, 2024 14:06 UTC   <invalid>                               no      
apiserver                  Jul 01, 2024 07:38 UTC   25d             ca                      no      
apiserver-etcd-client      Feb 16, 2024 14:06 UTC   <invalid>       etcd-ca                 no      
apiserver-kubelet-client   Feb 16, 2024 14:06 UTC   <invalid>       ca                      no      
controller-manager.conf    Feb 16, 2024 14:06 UTC   <invalid>                               no      
etcd-healthcheck-client    Feb 16, 2024 14:06 UTC   <invalid>       etcd-ca                 no      
etcd-peer                  Feb 16, 2024 14:06 UTC   <invalid>       etcd-ca                 no      
etcd-server                Feb 16, 2024 14:06 UTC   <invalid>       etcd-ca                 no      
front-proxy-client         Feb 16, 2024 14:06 UTC   <invalid>       front-proxy-ca          no      
scheduler.conf             Feb 16, 2024 14:06 UTC   <invalid>                               no      

CERTIFICATE AUTHORITY   EXPIRES                  RESIDUAL TIME   EXTERNALLY MANAGED
ca                      Feb 13, 2033 14:06 UTC   8y              no      
etcd-ca                 Feb 13, 2033 14:06 UTC   8y              no      
front-proxy-ca          Feb 13, 2033 14:06 UTC   8y              no

2. 重新签发证书

$ kubeadm 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 -o yaml'
[renew] Error reading configuration from the Cluster. Falling back to default configuration

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

Done renewing certificates. You must restart the kube-apiserver, kube-controller-manager, kube-scheduler and etcd, so that they can use the new certificates.

重新配置kubectl证书：
cp /etc/kubernetes/admin.conf ~/.kube/config -f

3. 重启控制面组件

由于控制面组件是由静态pod方式启动，将 /etc/kubernetes/manifests重命名，一分钟后改回，空静态pod会自动重启。
mv /etc/kubernetes/manifests /tmp/ && sleep 60 && mv /tmp/manifests /etc/kubernetes/
重新检查有效期：

$ kubeadm 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 -o yaml'

CERTIFICATE                EXPIRES                  RESIDUAL TIME   CERTIFICATE AUTHORITY   EXTERNALLY MANAGED
admin.conf                 Jun 06, 2025 03:10 UTC   364d                                    no      
apiserver                  Jun 06, 2025 03:10 UTC   364d            ca                      no      
apiserver-etcd-client      Jun 06, 2025 03:10 UTC   364d            etcd-ca                 no      
apiserver-kubelet-client   Jun 06, 2025 03:10 UTC   364d            ca                      no      
controller-manager.conf    Jun 06, 2025 03:10 UTC   364d                                    no      
etcd-healthcheck-client    Jun 06, 2025 03:10 UTC   364d            etcd-ca                 no      
etcd-peer                  Jun 06, 2025 03:10 UTC   364d            etcd-ca                 no      
etcd-server                Jun 06, 2025 03:10 UTC   364d            etcd-ca                 no      
front-proxy-client         Jun 06, 2025 03:10 UTC   364d            front-proxy-ca          no      
scheduler.conf             Jun 06, 2025 03:10 UTC   364d                                    no      

CERTIFICATE AUTHORITY   EXPIRES                  RESIDUAL TIME   EXTERNALLY MANAGED
ca                      Feb 13, 2033 14:06 UTC   8y              no      
etcd-ca                 Feb 13, 2033 14:06 UTC   8y              no      
front-proxy-ca          Feb 13, 2033 14:06 UTC   8y              no