kubeadm 是 kubernetes 提供的一个初始化集群的工具，使用起来非常方便。但是它创建的apiserver、controller-manager等证书默认只有一年的有效期，同时kubelet 证书也只有一年有效期，一年之后 kubernetes 将停止服务。官方推荐一年之内至少用 kubeadm upgrade 更新一次 kubernetes 系统，更新时也会自动更新证书。不过，在产线环境或者无法连接外网的环境频繁更新 kubernetes 不太现实。可以修改 kubeadm， 让它初始化集群时创建10年或其它有效期的apiserver、controller-manager证书，同时配合kubelet证书自动轮换机制来解决这个问题。
转载注明原作者地址：http://www.cnblogs.com/hahp
本文适用于 kubernetes 1.9.X
1. 修补 kubeadm
下面是我的源代码补丁，请给所需要的 kubernetes 版本打上，然后重新编译 kubeadm，用新编译的 kubeadm 初始化集群：
diff -Nur kubernetes.orig/vendor/k8s.io/client-go/util/cert/cert.go kubernetes/vendor/k8s.io/client-go/util/cert/cert.go
--- kubernetes.orig/vendor/k8s.io/client-go/util/cert/cert.go -- ::40.553612448 +
+++ kubernetes/vendor/k8s.io/client-go/util/cert/cert.go -- ::48.301330560 +
@@ -, +, @@
IPAddresses: cfg.AltNames.IPs,
SerialNumber: serial,
NotBefore: caCert.NotBefore,
- NotAfter: time.Now().Add(duration365d).UTC(),
+ NotAfter: time.Now().Add(duration365d * ).UTC(),
KeyUsage: x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature,
ExtKeyUsage: cfg.Usages,
}
@@ -, +, @@
CommonName: fmt.Sprintf("%s@%d", host, time.Now().Unix()),
},
NotBefore: time.Now(),
- NotAfter: time.Now().Add(time.Hour * * ),
+ NotAfter: time.Now().Add(time.Hour * * ), KeyUsage: x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature | x509.KeyUsageCertSign,
ExtKeyUsage: []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
2. 自动轮换 kubelet 证书
注：kubelet证书分为server和client两种， k8s 1.9默认启用了client证书的自动轮换，但server证书自动轮换需要用户开启。方法是：
2.1 增加 kubelet 参数
--feature-gates=RotateKubeletServerCertificate=true
2.2 增加 controller-manager 参数
--experimental-cluster-signing-duration=87600h0m0s
--feature-gates=RotateKubeletServerCertificate=true
2.3 创建 rbac 对象
创建rbac对象，允许节点轮换kubelet server证书：
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
annotations:
rbac.authorization.kubernetes.io/autoupdate: "true"
labels:
kubernetes.io/bootstrapping: rbac-defaults
name: system:certificates.k8s.io:certificatesigningrequests:selfnodeserver
rules:
- apiGroups:
- certificates.k8s.io
resources:
- certificatesigningrequests/selfnodeserver
verbs:
- create
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
name: kubeadm:node-autoapprove-certificate-server
roleRef:
apiGroup: rbac.authorization.k8s.io
kind: ClusterRole
name: system:certificates.k8s.io:certificatesigningrequests:selfnodeserver
subjects:
- apiGroup: rbac.authorization.k8s.io
kind: Group
name: system:nodes