K8S coreDNS部署及简单验证

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K8S coreDNS部署及简单验证

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因kube-dns社区不再维护，建议使用coredns进行相关dns部署
1. coreDNS安装
根据需要编辑coredns.yml

apiVersion: v1
kind: ServiceAccount
metadata:
  name: coredns
  namespace: kube-system
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  labels:
    kubernetes.io/bootstrapping: rbac-defaults
  name: system:coredns
rules:
- apiGroups:
  - ""
  resources:
  - endpoints
  - services
  - pods
  - namespaces
  verbs:
  - list
  - watch
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  annotations:
    rbac.authorization.kubernetes.io/autoupdate: "true"
  labels:
    kubernetes.io/bootstrapping: rbac-defaults
  name: system:coredns
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: system:coredns
subjects:
- kind: ServiceAccount
  name: coredns
  namespace: kube-system
---
apiVersion: v1
kind: ConfigMap
metadata:
  name: coredns
  namespace: kube-system
data:
  Corefile: |
    .:53 {
        errors
        health
        kubernetes cluster.local in-addr.arpa ip6.arpa {
           pods insecure
           upstream
           fallthrough in-addr.arpa ip6.arpa
        }
        prometheus :9153
        proxy . /etc/resolv.conf
        cache 30
        loop
        reload
        loadbalance
    }

---
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  labels:
    k8s-app: kube-dns
  name: coredns
  namespace: kube-system
spec:
  replicas: 1
  revisionHistoryLimit: 10
  selector:
    matchLabels:
      k8s-app: kube-dns
  strategy:
    rollingUpdate:
      maxSurge: 25%
      maxUnavailable: 1
    type: RollingUpdate
  template:
    metadata:
      labels:
        k8s-app: kube-dns
    spec:
      containers:
      - args:
        - -conf
        - /etc/coredns/Corefile
        image:  docker.io/fengyunpan/coredns:1.2.6
        imagePullPolicy: IfNotPresent
        livenessProbe:
          failureThreshold: 5
          httpGet:
            path: /health
            port: 8080
            scheme: HTTP
          initialDelaySeconds: 60
          periodSeconds: 10
          successThreshold: 1
          timeoutSeconds: 5
        name: coredns
        ports:
        - containerPort: 53
          name: dns
          protocol: UDP
        - containerPort: 53
          name: dns-tcp
          protocol: TCP
        - containerPort: 9153
          name: metrics
          protocol: TCP
        resources:
          limits:
            memory: 170Mi
          requests:
            cpu: 100m
            memory: 70Mi
        securityContext:
          allowPrivilegeEscalation: false
          capabilities:
            add:
            - NET_BIND_SERVICE
            drop:
            - all
          procMount: Default
          readOnlyRootFilesystem: true
        terminationMessagePath: /dev/termination-log
        terminationMessagePolicy: File
        volumeMounts:
        - mountPath: /etc/coredns
          name: config-volume
          readOnly: true
      dnsPolicy: Default
      restartPolicy: Always
      schedulerName: default-scheduler
      securityContext: {}
      serviceAccount: coredns
      serviceAccountName: coredns
      terminationGracePeriodSeconds: 30
      tolerations:
      - key: CriticalAddonsOnly
        operator: Exists
      - effect: NoSchedule
        key: node-role.kubernetes.io/master
      volumes:
      - configMap:
          defaultMode: 420
          items:
          - key: Corefile
            path: Corefile
          name: coredns
        name: config-volume

---
apiVersion: v1
kind: Service
metadata:
  labels:
    k8s-app: kube-dns
    kubernetes.io/cluster-service: "true"
    kubernetes.io/name: KubeDNS
  name: kube-dns
  namespace: kube-system
spec:
  selector:
    k8s-app: coredns
  clusterIP: 10.96.0.10
  ports:
  - name: dns
    port: 53
    protocol: UDP
    targetPort: 53
  - name: dns-tcp
    port: 53
    protocol: TCP
    targetPort: 53
  selector:
    k8s-app: kube-dns

创建coreDNS

kubectl create -f coredns.yml 

查看pod状态

kubectl -n kube-system get pod,svc -l k8s-app=kube-dns

NAME                           READY   STATUS    RESTARTS   AGE
pod/coredns-554589b9bd-xw7vh   1/1     Running   0          45m

NAME               TYPE        CLUSTER-IP   EXTERNAL-IP   PORT(S)         AGE
service/kube-dns   ClusterIP   10.96.0.10   <none>        53/UDP,53/TCP   45m

2. coreDNS验证
coreDNS使用buybox无法验证，可以使用dig进行验证
dig.yml如下：

apiVersion: v1
kind: Pod
metadata:
  name: dig
  namespace: default
spec:
  containers:
  - name: dig
    image:  docker.io/azukiapp/dig
    command:
      - sleep
      - "3600"
    imagePullPolicy: IfNotPresent
  restartPolicy: Always

创建dig

kubectl apply -f addons/coredns/dig.yml

解析dns，如有以下返回说明dns安装成功

kubectl exec -ti dig -- nslookup kubernetes
Server:        10.96.0.10
Address:    10.96.0.10#53

Name:    kubernetes.default.svc.cluster.local
Address: 10.96.0.1