安裝kubernetes-dashboard時顯示爲CrashLoopBackOff或Error狀態的可能原因

在CentOS7上安裝完K8S單Master+3Node集羣后，安裝kubernetes-dashboard時顯示爲CrashLoopBackOff或Error狀態：

kubernetes-dashboard   dashboard-metrics-scraper-6f669b9c9b-btkzj   1/1     Running            0
    2m3s
kubernetes-dashboard   kubernetes-dashboard-758765f476-x8rc7        0/1     CrashLoopBackOff   2 (12s ago

查看具體的Pod日誌：

[root@master1 ~]# kubectl logs -f -n kubernetes-dashboard kubernetes-dashboard-758765f476-x8rc7
2023/01/09 07:53:16 Using namespace: kubernetes-dashboard
2023/01/09 07:53:16 Using in-cluster config to connect to apiserver
2023/01/09 07:53:16 Starting overwatch
2023/01/09 07:53:16 Using secret token for csrf signing
2023/01/09 07:53:16 Initializing csrf token from kubernetes-dashboard-csrf secret
panic: Get "https://10.96.0.1:443/api/v1/namespaces/kubernetes-dashboard/secrets/kubernetes-dashboard-csrf": 
dial tcp 10.96.0.1:443: connect: no route to host

goroutine 1 [running]:
github.com/kubernetes/dashboard/src/app/backend/client/csrf.(*csrfTokenManager).init(0xc0004dfae8)
        /home/runner/work/dashboard/dashboard/src/app/backend/client/csrf/manager.go:41 +0x30e
github.com/kubernetes/dashboard/src/app/backend/client/csrf.NewCsrfTokenManager(...)
        /home/runner/work/dashboard/dashboard/src/app/backend/client/csrf/manager.go:66
github.com/kubernetes/dashboard/src/app/backend/client.(*clientManager).initCSRFKey(0xc000096b80)
        /home/runner/work/dashboard/dashboard/src/app/backend/client/manager.go:527 +0x94
github.com/kubernetes/dashboard/src/app/backend/client.(*clientManager).init(0x19aba3a?)
        /home/runner/work/dashboard/dashboard/src/app/backend/client/manager.go:495 +0x32
github.com/kubernetes/dashboard/src/app/backend/client.NewClientManager(...)
        /home/runner/work/dashboard/dashboard/src/app/backend/client/manager.go:594
main.main()
        /home/runner/work/dashboard/dashboard/src/app/backend/dashboard.go:96 +0x1cf

起初以爲是相關端口(例如443)沒在防火牆開放的原因，於是就把相關端口在所有機器上都開放了，並使用以下命令卸載乾淨了kubernetes-dashboard：

sudo kubectl delete deployment kubernetes-dashboard --namespace=kubernetes-dashboard 
sudo kubectl delete service kubernetes-dashboard  --namespace=kubernetes-dashboard 
sudo kubectl delete service dashboard-metrics-scraper  --namespace=kubernetes-dashboard 
sudo kubectl delete role.rbac.authorization.k8s.io kubernetes-dashboard --namespace=kubernetes-dashboard 
sudo kubectl delete clusterrole.rbac.authorization.k8s.io kubernetes-dashboard --namespace=kubernetes-dashboard
sudo kubectl delete rolebinding.rbac.authorization.k8s.io kubernetes-dashboard --namespace=kubernetes-dashboard
sudo kubectl delete clusterrolebinding.rbac.authorization.k8s.io kubernetes-dashboard --namespace=kubernetes-dashboard
sudo kubectl delete deployment.apps kubernetes-dashboard --namespace=kubernetes-dashboard
sudo kubectl delete deployment.apps dashboard-metrics-scraper --namespace=kubernetes-dashboard
sudo kubectl delete sa kubernetes-dashboard --namespace=kubernetes-dashboard 
sudo kubectl delete secret kubernetes-dashboard-certs --namespace=kubernetes-dashboard
sudo kubectl delete secret kubernetes-dashboard-csrf --namespace=kubernetes-dashboard
sudo kubectl delete secret kubernetes-dashboard-key-holder --namespace=kubernetes-dashboard
sudo kubectl delete namespace kubernetes-dashboard 
sudo kubectl delete configmap kubernetes-dashboard-settings 

重裝之後發現還是老子樣：

[root@master1 ~]# kubectl apply -f kubernetes-dashboard.yaml 

 於是乾脆將所有機器上的防火牆臨時關閉了：

[root@master1 ~]# systemctl stop firewalld

然後重新卸載乾淨kubernetes-dashboard，並進行重裝，結果還是報錯，但錯誤有一點點不一樣了：

[root@master1 ~]# kubectl logs -f -n kubernetes-dashboard kubernetes-dashboard-758765f476-g7lqs
2023/01/09 08:03:05 Starting overwatch
2023/01/09 08:03:05 Using namespace: kubernetes-dashboard
2023/01/09 08:03:05 Using in-cluster config to connect to apiserver
2023/01/09 08:03:05 Using secret token for csrf signing
2023/01/09 08:03:05 Initializing csrf token from kubernetes-dashboard-csrf secret
panic: Get "https://10.96.0.1:443/api/v1/namespaces/kubernetes-dashboard/secrets/kubernetes-dashboard-csrf": 
dial tcp 10.96.0.1:443: i/o timeout

goroutine 1 [running]:
github.com/kubernetes/dashboard/src/app/backend/client/csrf.(*csrfTokenManager).init(0xc00049fae8)
        /home/runner/work/dashboard/dashboard/src/app/backend/client/csrf/manager.go:41 +0x30e
github.com/kubernetes/dashboard/src/app/backend/client/csrf.NewCsrfTokenManager(...)
        /home/runner/work/dashboard/dashboard/src/app/backend/client/csrf/manager.go:66
github.com/kubernetes/dashboard/src/app/backend/client.(*clientManager).initCSRFKey(0xc0001c4100)
        /home/runner/work/dashboard/dashboard/src/app/backend/client/manager.go:527 +0x94
github.com/kubernetes/dashboard/src/app/backend/client.(*clientManager).init(0x19aba3a?)
        /home/runner/work/dashboard/dashboard/src/app/backend/client/manager.go:495 +0x32
github.com/kubernetes/dashboard/src/app/backend/client.NewClientManager(...)
        /home/runner/work/dashboard/dashboard/src/app/backend/client/manager.go:594
main.main()
        /home/runner/work/dashboard/dashboard/src/app/backend/dashboard.go:96 +0x1cf

此時可以確定的是——應該不是端口開放之類的防火牆問題了，因爲此時所有機器的防火牆都處於關閉狀態！所以網上其他兄弟說的執行：iptables -L -n --line-numbers | grep dashboard，發現是ipatables規則問題就不成立了，雖然我這裏也確實能查到相關攔截規則記錄：

[root@master1 ~]# iptables -L -n --line-numbers | grep dashboard
1    REJECT     tcp  --  0.0.0.0/0            0.0.0.0/0            /* kubernetes-dashboard/kubernetes-dashboard has no endpoints */ ADDRTYPE match dst-type LOCAL tcp dpt:32646 reject-with icmp-port-unreachable
1    REJECT     tcp  --  0.0.0.0/0            10.103.89.4          /* kubernetes-dashboard/kubernetes-dashboard has no endpoints */ tcp dpt:443 reject-with icmp-port-unreachable

經過多方查證，最後發現竟然是一開始使用 kubeadm init 命令初始化主節點Master時，配置文件裏的 podSubnet: 192.168.0.0/16 (或直接的命令參數--pod-network-cidr=192.168.0.0/16)的網段與當前Master節點的內網IP地址(192.168.17.3)網段重疊，導致在分配網絡的時候會出現問題，在安裝kubernetes-dashboard組件的時候Node工作節點和Master主節點之間無法互訪，導致安裝失敗。

解決辦法是：重新安裝k8s集羣

步驟是：

1、卸載乾淨了kubernetes-dashboard （見前文）

2、刪除Node節點

[root@master1 ~]# kubectl get nodes

[root@master1 ~]# kubectl drain node1.localk8s --delete-emptydir-data --force --ignore-daemonsets
[root@master1 ~]# kubectl drain node2.localk8s --delete-emptydir-data --force --ignore-daemonsets
[root@master1 ~]# kubectl drain node3.localk8s --delete-emptydir-data --force --ignore-daemonsets

[root@master1 ~]# kubectl delete nodes node1.localk8s node2.localk8s node3.localk8s

 

2、重置K8S集羣

[root@master1 ~]# kubeadm reset

3、刪除殘餘文件

[root@master1 ~]# rm -rf /etc/kubernetes
[root@master1 ~]# rm -rf /var/lib/etcd/
[root@master1 ~]# rm -rf $HOME/.kube

4、修改kubeadm init 初始化配置文件中的podSubnet，並保存

比如 podSubnet: 192.168.0.0/16 改爲 podSubnet: 192.169.0.0/16 

5、重新初始化K8S主節點

[root@master1 ~]# kubeadm init --config=/etc/kubeadm/init.default.yaml

後面重新將安裝K8S集羣安裝部署操作就行了，然後重新安裝kubernetes-dashboard

最後查看安裝結果：

[root@master1 ~]# kubectl get svc,pods  -n kubernetes-dashboard
NAME                                TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)         AGE
service/dashboard-metrics-scraper   ClusterIP   10.96.254.169   <none>        8000/TCP        67s
service/kubernetes-dashboard        NodePort    10.96.146.223   <none>        443:31529/TCP   67s

NAME                                             READY   STATUS    RESTARTS   AGE
pod/dashboard-metrics-scraper-6f669b9c9b-lcdnv   1/1     Running   0          67s
pod/kubernetes-dashboard-758765f476-vfjx5        1/1     Running   0          67s

現在可以根據結果中顯示的端口號，使用任意一個Node節點去訪問kubernetes-dashboard了：

獲取指定用戶(kubernetes-dashboard)的Token命令：

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

 

最後建議一下，最好在kubernetes-dashboard的yaml配置文件中，將dashboard的訪問端口一開始就固定下來：

增加一個nodePort: 31529 用於暴露服務
spec:
    type: NodePort
    ports:
      - prot: 443
        targetProt: 8443
        nodePort: 31529 

以下命令用於實時監控集羣內Pod的狀態：

----實時監控----
watch -n 3 kubectl get pods -A
----單次查看（可-n指定namespace）----
kubectl get pods -A -o wide

 附上kubernetes-dashboard v2.5.1 的配置文件(紅色爲自定義增加的配置)

Kubernetes version	1.20	1.21	1.22	1.23
Compatibility	?	?	?	✓

# 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:
  type: NodePort
  ports:
    - port: 443
      targetPort: 8443
      nodePort: 31529
  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:
      securityContext:
        seccompProfile:
          type: RuntimeDefault
      containers:
        - name: kubernetes-dashboard
          image: kubernetesui/dashboard:v2.5.1
          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
    spec:
      securityContext:
        seccompProfile:
          type: RuntimeDefault
      containers:
        - name: dashboard-metrics-scraper
          image: kubernetesui/metrics-scraper:v1.0.7
          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: {}