coredns.yaml文件如下所示

# __MACHINE_GENERATED_WARNING__apiVersion: v1kind: ServiceAccountmetadata:  name: coredns  namespace: kube-system  labels:      kubernetes.io/cluster-service: "true"      addonmanager.kubernetes.io/mode: Reconcile---apiVersion: rbac.authorization.k8s.io/v1kind: ClusterRolemetadata:  labels:    kubernetes.io/bootstrapping: rbac-defaults    addonmanager.kubernetes.io/mode: Reconcile  name: system:corednsrules:- apiGroups:  - ""  resources:  - endpoints  - services  - pods  - namespaces  verbs:  - list  - watch- apiGroups:  - ""  resources:  - nodes  verbs:  - get---apiVersion: rbac.authorization.k8s.io/v1kind: ClusterRoleBindingmetadata:  annotations:    rbac.authorization.kubernetes.io/autoupdate: "true"  labels:    kubernetes.io/bootstrapping: rbac-defaults    addonmanager.kubernetes.io/mode: EnsureExists  name: system:corednsroleRef:  apiGroup: rbac.authorization.k8s.io  kind: ClusterRole  name: system:corednssubjects:- kind: ServiceAccount  name: coredns  namespace: kube-system---apiVersion: v1kind: ConfigMapmetadata:  name: coredns  namespace: kube-system  labels:      addonmanager.kubernetes.io/mode: EnsureExistsdata:  Corefile: |    .:53 {        errors        health        kubernetes cluster.local in-addr.arpa ip6.arpa {            pods insecure            upstream            fallthrough in-addr.arpa ip6.arpa            ttl 30        }        prometheus :9153        forward . /etc/resolv.conf        cache 30        loop        reload        loadbalance    }---apiVersion: apps/v1kind: Deploymentmetadata:  name: coredns  namespace: kube-system  labels:    k8s-app: kube-dns    kubernetes.io/cluster-service: "true"    addonmanager.kubernetes.io/mode: Reconcile    kubernetes.io/name: "CoreDNS"spec:  # replicas: not specified here:  # 1. In order to make Addon Manager do not reconcile this replicas parameter.  # 2. Default is 1.  # 3. Will be tuned in real time if DNS horizontal auto-scaling is turned on.  strategy:    type: RollingUpdate    rollingUpdate:      maxUnavailable: 1  selector:    matchLabels:      k8s-app: kube-dns  template:    metadata:      labels:        k8s-app: kube-dns      annotations:        seccomp.security.alpha.kubernetes.io/pod: 'docker/default'    spec:      priorityClassName: system-cluster-critical      serviceAccountName: coredns      tolerations:        - key: "CriticalAddonsOnly"          operator: "Exists"      nodeSelector:        beta.kubernetes.io/os: linux      containers:      - name: coredns        image: k8s.gcr.io/coredns:1.3.1        imagePullPolicy: IfNotPresent        resources:          limits:            memory: 70Mi          requests:            cpu: 100m            memory: 70Mi        args: [ "-conf", "/etc/coredns/Corefile" ]        volumeMounts:        - name: config-volume          mountPath: /etc/coredns          readOnly: true        ports:        - containerPort: 53          name: dns          protocol: UDP        - containerPort: 53          name: dns-tcp          protocol: TCP        - containerPort: 9153          name: metrics          protocol: TCP        livenessProbe:          httpGet:            path: /health            port: 8080            scheme: HTTP          initialDelaySeconds: 60          timeoutSeconds: 5          successThreshold: 1          failureThreshold: 5        readinessProbe:          httpGet:            path: /health            port: 8080            scheme: HTTP        securityContext:          allowPrivilegeEscalation: false          capabilities:            add:            - NET_BIND_SERVICE            drop:            - all          readOnlyRootFilesystem: true      dnsPolicy: Default      volumes:        - name: config-volume          configMap:            name: coredns            items:            - key: Corefile              path: Corefile---apiVersion: v1kind: Servicemetadata:  name: kube-dns  namespace: kube-system  annotations:    prometheus.io/port: "9153"    prometheus.io/scrape: "true"  labels:    k8s-app: kube-dns    kubernetes.io/cluster-service: "true"    addonmanager.kubernetes.io/mode: Reconcile    kubernetes.io/name: "CoreDNS"spec:  selector:    k8s-app: kube-dns  clusterIP: 10.0.0.2  ports:  - name: dns    port: 53    protocol: UDP  - name: dns-tcp    port: 53    protocol: TCP  - name: metrics    port: 9153    protocol: TCP

修改以上yaml文件中红色部分修改成自己对于的信息

kubectl apply -f coredns.yaml

执行apply  生成pod（需要替换镜像，不然会拉取失败）

[root@k8s-master yaml]# kubectl get all -n kube-system | grep corednspod/coredns-867ccfd476-9ghff              1/1     Running   13         42hpod/coredns-867ccfd476-p5md4              1/1     Running   15         42hdeployment.apps/coredns                2/2     2            2           44hreplicaset.apps/coredns-867ccfd476              2         2         2       44h[root@k8s-master yaml]#

创建测试的pod

[root@k8s-master test]# cat my-apache.yaml apiVersion: extensions/v1beta1kind: Deploymentmetadata:  name: my-apachespec:  replicas: 2  template:    metadata:      labels:        run: my-apache    spec:      containers:      - name: my-apache        image: httpd:2.4        ports:        - containerPort: 80---apiVersion: v1kind: Servicemetadata:  name: my-apache  labels:    run: my-apachespec:  type: NodePort  ports:  - port: 80    targetPort: 80    nodePort: 30002  selector:    run: my-apache

生成pod

[root@k8s-master test]# kubectl apply -f my-apache.yaml

查看pod运行状态

[root@k8s-master test]# kubectl get pod NAME                         READY   STATUS    RESTARTS   AGEmy-apache-75f574f468-8psfw   1/1     Running   1          24hmy-apache-75f574f468-msrrn   1/1     Running   0          24h[root@k8s-master test]#

已经全部运行

[root@k8s-master test]# kubectl get svc NAME         TYPE        CLUSTER-IP   EXTERNAL-IP   PORT(S)        AGEkubernetes   ClusterIP   10.0.0.1     
     
              443/TCP        2dmy-apache    NodePort    10.0.0.71    
      
               80:30002/TCP   24h[root@k8s-master test]# curl 10.0.0.71
       
It works!
[root@k8s-master test]#
      
     

由此可见dns服务是可用的