一、前言

上一篇文章介绍了从零开始搭建Kubernetes集群,本文将介绍一下如何搭建K8S的Dashboard。

简单的说,K8S Dashboard是官方的一个基于WEB的用户界面,专门用来管理K8S集群,并展示集群的状态。K8S集群安装好后默认没有包含Dashboard,我们需要额外创建它。

Dashboard设计的还不错,界面友好,功能也比较强大。如果你厌倦了命令行的操作,全程使用Dashboard也是可行的。

因为我们使用kubeadm搭建的集群会默认开启RABC(角色访问控制机制),所以我们必须要进行额外的设置。关于RABC的概念,网上资料很多,大家务必提前了解。

二、RBAC简介

RBAC(Role-Based Access Control )基于角色的访问控制,不懂的可以百度看下
K8S 1.6引进,是让用户能够访问 k8S API 资源的授权方式【不授权就没有资格访问K8S的资源】

2.1、用户

K8S有两种用户:User和Service Account。其中,User给人用,Service Account给进程用,让进程有相关权限。如Dashboard就是一个进程,我们就可以创建一个Service Account给它

2.2、角色

Role是一系列权限的集合,例如一个Role可包含读取和列出 Pod的权限【 ClusterRole 和 Role 类似,其权限范围是整个集群】

2.3、角色绑定

RoleBinding把角色映射到用户,从而让这些用户拥有该角色的权限【ClusterRoleBinding 和RoleBinding 类似,可让用户拥有 ClusterRole 的权限】

2.4、Secret

Secret是一个包含少量敏感信息如密码,令牌,或秘钥的对象。把这些信息保存在 Secret对象中,可以在这些信息被使用时加以控制,并可以降低信息泄露的风险
如下图,灰色是“角色”,蓝色是“用户”,绿色是“角色绑定”,黄色是该角色拥有的权限。简言之 ,角色绑定将角色和用户进行挂钩:
在这里插入图片描述

三、安装Kubernetes-Dashboard

官方文档:Web UI (K8S Dashboard)

3.1、部署

参考官方文档,在部署好了 k8s 集群环境的前提下,要安装 Kubernetes-Dashboard 只需要一条命令就可以搞定,如下:

kubectl apply -f https://raw.githubusercontent.com/kubernetes/dashboard/v2.0.0/aio/deploy/recommended.yaml

确实如此,但是要通过页面访问还需要进行其他操作

3.2、访问

要想通过页面访问,我们可以先大致看下 recommended.yaml,理解下其中的内容

3.2.1、recommended.yaml 内容

# Copyright 2017 The Kubernetes Authors.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

apiVersion: v1
kind: Namespace
metadata:
  name: kubernetes-dashboard

---

apiVersion: v1
kind: ServiceAccount
metadata:
  labels:
    k8s-app: kubernetes-dashboard
  name: kubernetes-dashboard
  namespace: kubernetes-dashboard

---

kind: Service
apiVersion: v1
metadata:
  labels:
    k8s-app: kubernetes-dashboard
  name: kubernetes-dashboard
  namespace: kubernetes-dashboard
spec:
  ports:
    - port: 443
      targetPort: 8443
  selector:
    k8s-app: kubernetes-dashboard

---

apiVersion: v1
kind: Secret
metadata:
  labels:
    k8s-app: kubernetes-dashboard
  name: kubernetes-dashboard-certs
  namespace: kubernetes-dashboard
type: Opaque

---

apiVersion: v1
kind: Secret
metadata:
  labels:
    k8s-app: kubernetes-dashboard
  name: kubernetes-dashboard-csrf
  namespace: kubernetes-dashboard
type: Opaque
data:
  csrf: ""

---

apiVersion: v1
kind: Secret
metadata:
  labels:
    k8s-app: kubernetes-dashboard
  name: kubernetes-dashboard-key-holder
  namespace: kubernetes-dashboard
type: Opaque

---

kind: ConfigMap
apiVersion: v1
metadata:
  labels:
    k8s-app: kubernetes-dashboard
  name: kubernetes-dashboard-settings
  namespace: kubernetes-dashboard

---

kind: Role
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  labels:
    k8s-app: kubernetes-dashboard
  name: kubernetes-dashboard
  namespace: kubernetes-dashboard
rules:
  # Allow Dashboard to get, update and delete Dashboard exclusive secrets.
  - apiGroups: [""]
    resources: ["secrets"]
    resourceNames: ["kubernetes-dashboard-key-holder", "kubernetes-dashboard-certs", "kubernetes-dashboard-csrf"]
    verbs: ["get", "update", "delete"]
    # Allow Dashboard to get and update 'kubernetes-dashboard-settings' config map.
  - apiGroups: [""]
    resources: ["configmaps"]
    resourceNames: ["kubernetes-dashboard-settings"]
    verbs: ["get", "update"]
    # Allow Dashboard to get metrics.
  - apiGroups: [""]
    resources: ["services"]
    resourceNames: ["heapster", "dashboard-metrics-scraper"]
    verbs: ["proxy"]
  - apiGroups: [""]
    resources: ["services/proxy"]
    resourceNames: ["heapster", "http:heapster:", "https:heapster:", "dashboard-metrics-scraper", "http:dashboard-metrics-scraper"]
    verbs: ["get"]

---

kind: ClusterRole
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  labels:
    k8s-app: kubernetes-dashboard
  name: kubernetes-dashboard
rules:
  # Allow Metrics Scraper to get metrics from the Metrics server
  - apiGroups: ["metrics.k8s.io"]
    resources: ["pods", "nodes"]
    verbs: ["get", "list", "watch"]

---

apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
  labels:
    k8s-app: kubernetes-dashboard
  name: kubernetes-dashboard
  namespace: kubernetes-dashboard
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: Role
  name: kubernetes-dashboard
subjects:
  - kind: ServiceAccount
    name: kubernetes-dashboard
    namespace: kubernetes-dashboard

---

apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  name: kubernetes-dashboard
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: kubernetes-dashboard
subjects:
  - kind: ServiceAccount
    name: kubernetes-dashboard
    namespace: kubernetes-dashboard

---

kind: Deployment
apiVersion: apps/v1
metadata:
  labels:
    k8s-app: kubernetes-dashboard
  name: kubernetes-dashboard
  namespace: kubernetes-dashboard
spec:
  replicas: 1
  revisionHistoryLimit: 10
  selector:
    matchLabels:
      k8s-app: kubernetes-dashboard
  template:
    metadata:
      labels:
        k8s-app: kubernetes-dashboard
    spec:
      containers:
        - name: kubernetes-dashboard
          image: kubernetesui/dashboard:v2.0.0
          imagePullPolicy: Always
          ports:
            - containerPort: 8443
              protocol: TCP
          args:
            - --auto-generate-certificates
            - --namespace=kubernetes-dashboard
            # Uncomment the following line to manually specify Kubernetes API server Host
            # If not specified, Dashboard will attempt to auto discover the API server and connect
            # to it. Uncomment only if the default does not work.
            # - --apiserver-host=http://my-address:port
          volumeMounts:
            - name: kubernetes-dashboard-certs
              mountPath: /certs
              # Create on-disk volume to store exec logs
            - mountPath: /tmp
              name: tmp-volume
          livenessProbe:
            httpGet:
              scheme: HTTPS
              path: /
              port: 8443
            initialDelaySeconds: 30
            timeoutSeconds: 30
          securityContext:
            allowPrivilegeEscalation: false
            readOnlyRootFilesystem: true
            runAsUser: 1001
            runAsGroup: 2001
      volumes:
        - name: kubernetes-dashboard-certs
          secret:
            secretName: kubernetes-dashboard-certs
        - name: tmp-volume
          emptyDir: {}
      serviceAccountName: kubernetes-dashboard
      nodeSelector:
        "kubernetes.io/os": linux
      # Comment the following tolerations if Dashboard must not be deployed on master
      tolerations:
        - key: node-role.kubernetes.io/master
          effect: NoSchedule

---

kind: Service
apiVersion: v1
metadata:
  labels:
    k8s-app: dashboard-metrics-scraper
  name: dashboard-metrics-scraper
  namespace: kubernetes-dashboard
spec:
  ports:
    - port: 8000
      targetPort: 8000
  selector:
    k8s-app: dashboard-metrics-scraper

---

kind: Deployment
apiVersion: apps/v1
metadata:
  labels:
    k8s-app: dashboard-metrics-scraper
  name: dashboard-metrics-scraper
  namespace: kubernetes-dashboard
spec:
  replicas: 1
  revisionHistoryLimit: 10
  selector:
    matchLabels:
      k8s-app: dashboard-metrics-scraper
  template:
    metadata:
      labels:
        k8s-app: dashboard-metrics-scraper
      annotations:
        seccomp.security.alpha.kubernetes.io/pod: 'runtime/default'
    spec:
      containers:
        - name: dashboard-metrics-scraper
          image: kubernetesui/metrics-scraper:v1.0.4
          ports:
            - containerPort: 8000
              protocol: TCP
          livenessProbe:
            httpGet:
              scheme: HTTP
              path: /
              port: 8000
            initialDelaySeconds: 30
            timeoutSeconds: 30
          volumeMounts:
          - mountPath: /tmp
            name: tmp-volume
          securityContext:
            allowPrivilegeEscalation: false
            readOnlyRootFilesystem: true
            runAsUser: 1001
            runAsGroup: 2001
      serviceAccountName: kubernetes-dashboard
      nodeSelector:
        "kubernetes.io/os": linux
      # Comment the following tolerations if Dashboard must not be deployed on master
      tolerations:
        - key: node-role.kubernetes.io/master
          effect: NoSchedule
      volumes:
        - name: tmp-volume
          emptyDir: {}
3.2.1.1、recommended中包括了下面几个组件
  • Dashboard Service
  • Dashboard Deployment
  • Dashboard Role
  • RoleBinding
  • Dashboard Service Account
  • Dashboard Secret

Dashboard Service

kind: Service
...
k8s-app: kubernetes-dashboard
...
spec:
  type: NodePort
  ports:
    - port: 443 
      targetPort: 8443
      nodePort: 30000

Dashboard 对外提供服务设置,也指定了nodePort,这样我们可以通过物理机上的30000端口进行访问

Dashboard Deployment

kind: Deployment
...
k8s-app: kubernetes-dashboard
....

Dashboard的Deployment指定了其使用的ServiceAccount是kubernetes-dashboard。并且还将Secret kubernetes-dashboard-certs通过volumes挂在到pod内部的/certs路径。为何要挂载Secret ?原因是创建Secret 时会自动生成token。请注意参数–auto-generate-certificates,其表示Dashboard会自动生成证书。

Dashboard Role

kind: Role
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  labels:
    k8s-app: kubernetes-dashboard
  name: kubernetes-dashboard
  namespace: kubernetes-dashboard
rules:
...

如上定义了Dashboard 的角色,其角色名称为 kubernetes-dashboard,rules中清晰的列出了其拥有的多个权限。

RoleBinding

apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
  labels:
    k8s-app: kubernetes-dashboard
  name: kubernetes-dashboard
  namespace: kubernetes-dashboard
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: Role
  name: kubernetes-dashboard
subjects:
  - kind: ServiceAccount
    name: kubernetes-dashboard
    namespace: kubernetes-dashboard

Dashboard的角色绑定,其名称为 kubernetes-dashboard,roleRef 中为被绑定的角色,subjects中为绑定的用户:kubernetes-dashboard

Dashboard Service Account

apiVersion: v1
kind: ServiceAccount
metadata:
  labels:
    k8s-app: kubernetes-dashboard
  name: kubernetes-dashboard
  namespace: kubernetes-dashboard

如上定义了Dashboard的用户,其类型为ServiceAccount,名称为kubernetes-dashboard

Dashboard Secret

apiVersion: v1
kind: Secret
...

3.3.2、web 页面

通过暴露的NodePort: 30000 访问 dashboard,页面如图(我这里通过 firefox 才能访问,chrome 都不行):https://localhost:30000/
在这里插入图片描述
这里有两种登录方式:

  • Token
  • Kubeconfig

我们使用 Token 的方式登录,获取 Token 方式如下:

kubectl -n kubernetes-dashboard describe secret $(kubectl -n kubernetes-dashboard get secret | grep kubernetes-dashboard | awk '{print $1}')

在这里插入图片描述
复制token,点击登录即可

3.3、到这里还没有完

通过3.2的步骤会出现下面问题:
在这里插入图片描述
出现上述问题的原因是因为,kubernetes-dashboard 这个账户的角色权限不够

解决:

3.3.3、创建dashboard-adminuser.yaml

cat > dashboard-adminuser.yaml << EOF
apiVersion: v1
kind: ServiceAccount
metadata:
  name: admin-user
  namespace: kubernetes-dashboard

---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  name: admin-user
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: cluster-admin
subjects:
- kind: ServiceAccount
  name: admin-user
  namespace: kubernetes-dashboard  
EOF

3.3.2、创建登录用户

kubectl apply -f dashboard-adminuser.yaml

说明:上面创建了一个叫 admin-user 的服务账号,并放在kubernetes-dashboard 命名空间下,并将 cluster-admin 角色绑定到admin-user账户,这样admin-user账户就有了管理员的权限。默认情况下,kubeadm创建集群时已经创建了cluster-admin角色,我们直接绑定即可。

3.3.3、查看admin-user账户的token

kubectl -n kubernetes-dashboard describe secret $(kubectl -n kubernetes-dashboard get secret | grep admin-user | awk '{print $1}')

重新登录即可
在这里插入图片描述

四、一些命令

# 查看dashboard的角色(Role)
kubectl get role -n kubernetes-dashboard
# 查看dashboard的账户
kubectl get ServiceAccount -n kubernetes-dashboard
# 查看secret
kubectl get secret -n kuberntes-dashboard
# 查看集群的角色(ClusterRole)
kubectl get ClusterRole -n kubernetes-dashboard
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