最近在看cncf，PV/PVC这块之前使用kubernetes时候还不成熟，准备复习下，准备使用nfs 来学习下，在使用dynamic 模式，部署nfs-client-provisioner 失败，使用kubectl logs 查看对应对应pod，报如下错误：

1 provisioner.go:180] Error getting server version: Get https://10.96.0.1:443/version?timeout=32s: dial tcp 10.96.0.1:443: i/o timeout

查看provisioner.go 代码，发现是

serverVersion, err := clientset.Discovery().ServerVersion()
	if err != nil {
		glog.Fatalf("Error getting server version: %v", err)
	}

发现是标准访问kubernetes api的连接，理论上应该不会有问题，进一步查看发现这个ip是

NAME         TYPE        CLUSTER-IP   EXTERNAL-IP   PORT(S)   AGE
kubernetes   ClusterIP   10.96.0.1    <none>        443/TCP   41m

再查看kubernetes 启动的进程

[root@master ~]# ps -ef|grep kube|grep 10.96
root      17570  17507  1 06:15 ?        00:00:33 kube-apiserver --advertise-address=192.168.157.132 --allow-privileged=true --authorization-mode=Node,RBAC --client-ca-file=/etc/kubernetes/pki/ca.crt --enable-admission-plugins=NodeRestriction --enable-bootstrap-token-auth=true --etcd-cafile=/etc/kubernetes/pki/etcd/ca.crt --etcd-certfile=/etc/kubernetes/pki/apiserver-etcd-client.crt --etcd-keyfile=/etc/kubernetes/pki/apiserver-etcd-client.key --etcd-servers=https://127.0.0.1:2379 --insecure-port=0 --kubelet-client-certificate=/etc/kubernetes/pki/apiserver-kubelet-client.crt --kubelet-client-key=/etc/kubernetes/pki/apiserver-kubelet-client.key --kubelet-preferred-address-types=InternalIP,ExternalIP,Hostname --proxy-client-cert-file=/etc/kubernetes/pki/front-proxy-client.crt --proxy-client-key-file=/etc/kubernetes/pki/front-proxy-client.key --requestheader-allowed-names=front-proxy-client --requestheader-client-ca-file=/etc/kubernetes/pki/front-proxy-ca.crt --requestheader-extra-headers-prefix=X-Remote-Extra- --requestheader-group-headers=X-Remote-Group --requestheader-username-headers=X-Remote-User --secure-port=6443 --service-account-key-file=/etc/kubernetes/pki/sa.pub --service-cluster-ip-range=10.96.0.0/12 --tls-cert-file=/etc/kubernetes/pki/apiserver.crt --tls-private-key-file=/etc/kubernetes/pki/apiserver.key

感觉也没有问题，突然想到是否由于flannel网络问题导致呢，查到如下blog
https://gravitational.com/blog/kubernetes-flannel-dashboard-bomb/

发现果然如此，使用 kubectl edit cm -n kube-system kube-flannel-cfg 查看到如下内容：

apiVersion: v1
data:
  cni-conf.json: |
    {
      "name": "cbr0",
      "cniVersion": "0.3.1",
      "plugins": [
        {
          "type": "flannel",
          "delegate": {
            "hairpinMode": true,
            "isDefaultGateway": true
          }
        },
        {
          "type": "portmap",
          "capabilities": {
            "portMappings": true
          }
        }
      ]
    }
  net-conf.json: |
    {
      "Network": "10.244.0.0/16",
      "Backend": {
        "Type": "vxlan"
      }
    }

重新安装kubernetes 使用默认–pod-network-cidr=10.244.0.0/16 ,done.