首先，如果是普通版kubernetes集群，可以登陆到master集群，可以使用私钥证书的方式访问。证书路径：master的/etc/kubernetes/pki 下面。 

使用命令：

curl --cacert ca.crt --cert apiserver.crt --key apiserver.key https://$server/api

server是apiserver公网访问地址



curl --cacert ca.crt --cert apiserver.crt --key apiserver.key https://server:6443/api

{

  "kind": "APIVersions",

  "versions": [

    "v1"

  ],

  "serverAddressByClientCIDRs": [

    {

      "clientCIDR": "0.0.0.0/0",

      "serverAddress": "192.168.0.251:6443"

    }

  ]


}

  接下来介绍一下使用ServiceAccount Token的方式访问集群。serviceaccount的权限由集群中对应的rolebinding决定，官方文档               https://kubernetes.io/docs/reference/access-authn-authz/rbac/

  请选择对应权限的ServiceAccount来获取token，我这边选择的是admin ServiceAccount

kubectl get sa admin -n kube-system -o yaml
apiVersion: v1
kind: ServiceAccount
metadata:
  annotations:
    kubectl.kubernetes.io/last-applied-configuration: |
      {"apiVersion":"v1","kind":"ServiceAccount","metadata":{"annotations":{},"name":"admin","namespace":"kube-system"}}
  creationTimestamp: 2018-11-05T09:23:39Z
  name: admin
  namespace: kube-system
  resourceVersion: "889"
  selfLink: /api/v1/namespaces/kube-system/serviceaccounts/admin
  uid: 7af4f177-e0dc-11e8-8ef4-00163e009d2a
secrets:
- name: admin-token-5tctj

查看对应的clusterrolebinding：
kubectl get clusterrolebinding admin -oyaml
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  annotations:
    kubectl.kubernetes.io/last-applied-configuration: |
      {"apiVersion":"rbac.authorization.k8s.io/v1beta1","kind":"ClusterRoleBinding","metadata":{"annotations":{},"name":"admin","namespace":""},"roleRef":{"apiGroup":"rbac.authorization.k8s.io","kind":"ClusterRole","name":"cluster-admin"},"subjects":[{"kind":"ServiceAccount","name":"admin","namespace":"kube-system"}]}
  creationTimestamp: 2018-11-05T09:23:39Z
  name: admin
  resourceVersion: "886"
  selfLink: /apis/rbac.authorization.k8s.io/v1/clusterrolebindings/admin
  uid: 7af6ff9d-e0dc-11e8-8ef4-00163e009d2a
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: cluster-admin
subjects:
- kind: ServiceAccount
  name: admin
  namespace: kube-system

查看admin sa绑定的clusterrole和对应的权限。命令：
kubectl get clusterrole cluster-admin -o yaml
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  annotations:
    rbac.authorization.kubernetes.io/autoupdate: "true"
  creationTimestamp: 2018-11-05T09:18:49Z
  labels:
    kubernetes.io/bootstrapping: rbac-defaults
  name: cluster-admin
  resourceVersion: "38"
  selfLink: /apis/rbac.authorization.k8s.io/v1/clusterroles/cluster-admin
  uid: ce28c0e7-e0db-11e8-9852-00163e009d2a
rules:
- apiGroups:
  - '*'
  resources:
  - '*'
  verbs:
  - '*'
- nonResourceURLs:
  - '*'
  verbs:
  - '*'

获取对应sa的secret从中获取token。并进行base64解码。

kubectl get secret admin-token-5tctj -n kube-system -o jsonpath={".data.token"} | base64 -d
eyJhbGciOiJSUzI1NiIsImtpZCI6IiJ9.eyJpc3MiOiJrdWJlcm5ldGVzL3NlcnZpY2VhY2NvdW50Iiwia3ViZXJuZXRlcy5pby9zZXJ2aWNlYWNjb3VudC9uYW1lc3BhY2UiOiJrdWJlLXN5c3RlbSIsImt1YmVybmV0ZXMuaW8vc2VydmljZWFjY291bnQvc2VjcmV0Lm5hbWUiOiJhZG1pbi10b2tlbi01dGN0aiIsImt1YmVybmV0ZXMuaW8vc2VydmljZWFjY291bnQvc2VydmljZS1hY2NvdW50Lm5hbWUiOiJhZG1pbiIsImt1YmVybmV0ZXMuaW8vc2VydmljZWFjY291bnQvc2VydmljZS1hY2NvdW50LnVpZCI6IjdhZjRmMTc3LWUwZGMtMTFlOC04ZWY0LTAwMTYzZTAwOWQyYSIsInN1YiI6InN5c3RlbTpzZXJ2aWNlYWNjb3VudDprdWJlLXN5c3RlbTphZG1pbiJ9.aMzef7qssxhFCkKHYFX99XBCkA_lnpKQhBvWPJ_AEsg89HUJ9cgYs2M7VRQJ2KcsG1BndSW0Ne-yLdsXFGDMaIRF58Rz02V99ViqAH8W86UZqcgARlw6DbYtpyHx2LZp4_HbrOy0xHJXGOx0FzwbCNJR5TE5LAZWx2Q5WowuxzdIhpkr15tn9UTZB0i2VXyANG3D6xyf1M67ojav59eC04qWu3ZuFC2GgngHGbZ1qnP55UnFTHWdFtHAzU5qAX7jrWJAOBdSPXwoxC9XTIBoL2umQk2XQN-OsBnQ_saXXLPe2cdpKdoboJCZgcUfO-5D94KO-5P8wNVhGWubNutvug

最后使用该token访问apiserver：
最后使用公网slb地址访问。curl -k -H 'Authorization: Bearer token' https://111.111.111.111:6443
例如：
curl -k -H 'Authorization: Bearer eyJhbGciOiJSUzI1NiIsImtpZCI6IiJ9.eyJpc3MiOiJrdWJlcm5ldGVzL3NlcnZpY2VhY2NvdW50Iiwia3ViZXJuZXRlcy5pby9zZXJ2aWNlYWNjb3VudC9uYW1lc3BhY2UiOiJrdWJlLXN5c3RlbSIsImt1YmVybmV0ZXMuaW8vc2VydmljZWFjY291bnQvc2VjcmV0Lm5hbWUiOiJhZG1pbi10b2tlbi01dGN0aiIsImt1YmVybmV0ZXMuaW8vc2VydmljZWFjY291bnQvc2VydmljZS1hY2NvdW50Lm5hbWUiOiJhZG1pbiIsImt1YmVybmV0ZXMuaW8vc2VydmljZWFjY291bnQvc2VydmljZS1hY2NvdW50LnVpZCI6IjdhZjRmMTc3LWUwZGMtMTFlOC04ZWY0LTAwMTYzZTAwOWQyYSIsInN1YiI6InN5c3RlbTpzZXJ2aWNlYWNjb3VudDprdWJlLXN5c3RlbTphZG1pbiJ9.aMzef7qssxhFCkKHYFX99XBCkA_lnpKQhBvWPJ_AEsg89HUJ9cgYs2M7VRQJ2KcsG1BndSW0Ne-yLdsXFGDMaIRF58Rz02V99ViqAH8W86UZqcgARlw6DbYtpyHx2LZp4_HbrOy0xHJXGOx0FzwbCNJR5TE5LAZWx2Q5WowuxzdIhpkr15tn9UTZB0i2VXyANG3D6xyf1M67ojav59eC04qWu3ZuFC2GgngHGbZ1qnP55UnFTHWdFtHAzU5qAX7jrWJAOBdSPXwoxC9XTIBoL2umQk2XQN-OsBnQ_saXXLPe2cdpKdoboJCZgcUfO-5D94KO-5P8wNVhGWubNutvug' https://111.111.111.111:6443/api
{
  "kind": "APIVersions",
  "versions": [
    "v1"
  ],
  "serverAddressByClientCIDRs": [
    {
      "clientCIDR": "0.0.0.0/0",
      "serverAddress": "192.168.0.252:6443"
    }
  ]
}