Kubernetes 部署 CoreDNS 组件

环境

• 二进制部署的 kubernetes v1.12.6 集群
• coreDNS 1.2.2

---

生成 service account 文件

• 创建 0.coredns-sa.yml

  cat > 0.coredns-sa.yml <<EOF
  apiVersion: v1
  kind: ServiceAccount
  metadata:
    name: coredns
    namespace: kube-system
  EOF
  

---

生成 rbac 文件

• 创建 1.coredns-rbac.yml

  curl > 1.coredns-rbac.yml <<EOF
  apiVersion: rbac.authorization.k8s.io/v1
  kind: ClusterRole
  metadata:
    labels:
      kubernetes.io/bootstrapping: rbac-defaults
      addonmanager.kubernetes.io/mode: Reconcile
    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
      addonmanager.kubernetes.io/mode: EnsureExists
    name: system:coredns
  roleRef:
    apiGroup: rbac.authorization.k8s.io
    kind: ClusterRole
    name: system:coredns
  subjects:
  - kind: ServiceAccount
    name: coredns
    namespace: kube-system
  EOF
  

---

生成 configmap 文件

• 创建 2.coredns-configmap.yml

  cat > 2.coredns-configmap.yml <<EOF
  apiVersion: v1
  kind: ConfigMap
  metadata:
    name: coredns
    namespace: kube-system
    labels:
      addonmanager.kubernetes.io/mode: EnsureExists
  data:
    Corefile: |
      .:53 {
          errors
          log stdout
          health
          kubernetes cluster.local 10.10.9.0/24
          proxy . /etc/resolv.conf
          cache 30
      }
  EOF
  

• 这里的 10.10.9.0/24 应与 kube-apiserver 配置文件中的 service-cluster-ip-range 一致
• 这里的 cluster.local 应与 kubelet 配置文件中的 clusterDomain 一致

---

生成 deployment 文件

• 创建 3.coredns-deployment.yml

  cat > 3.coredns-deployment.yml <<EOF
  apiVersion: extensions/v1beta1
  kind: Deployment
  metadata:
    name: coredns
    namespace: kube-system
    labels:
      k8s-app: coredns
      kubernetes.io/cluster-service: "true"
      addonmanager.kubernetes.io/mode: Reconcile
      kubernetes.io/name: "CoreDNS"
  spec:
    replicas: 2
    strategy:
      type: RollingUpdate
      rollingUpdate:
        maxUnavailable: 1
    selector:
      matchLabels:
        k8s-app: coredns
    template:
      metadata:
        labels:
          k8s-app: coredns
      spec:
        serviceAccountName: coredns
        containers:
        - name: coredns
          image: coredns/coredns:1.2.2
          imagePullPolicy: IfNotPresent
          resources:
            limits:
              memory: 170Mi
            requests:
              cpu: 100m
              memory: 70Mi
          args: [ "-conf", "/etc/coredns/Corefile" ]
          volumeMounts:
          - name: config-volume
            mountPath: /etc/coredns
            readOnly: true
          - name: tmp
            mountPath: /tmp
          ports:
          - containerPort: 53
            name: dns
            protocol: UDP
          - containerPort: 53
            name: dns-tcp
            protocol: TCP
          livenessProbe:
            httpGet:
              path: /health
              port: 8080
              scheme: HTTP
            initialDelaySeconds: 60
            timeoutSeconds: 5
            successThreshold: 1
            failureThreshold: 5
        dnsPolicy: Default
        volumes:
        - name: tmp
          emptyDir: {}
        - name: config-volume
          configMap:
            name: coredns
            items:
            - key: Corefile
              path: Corefile
  EOF
  

• coredns/coredns:1.2.2 该镜像可以提前导入本地局域网中的私有 docker 仓库中
• 查看 k8s 对应的 coredns 版本，参考 coredns

---

生成 service 文件

• 创建 4.coredns-service.yml

  cat > 4.coredns-service.yml <<EOF
  apiVersion: v1
  kind: Service
  metadata:
    name: coredns
    namespace: kube-system
    labels:
      k8s-app: coredns
      kubernetes.io/cluster-service: "true"
      addonmanager.kubernetes.io/mode: Reconcile
      kubernetes.io/name: "CoreDNS"
  spec:
    selector:
      k8s-app: coredns
    clusterIP: 10.10.9.2
    ports:
    - name: dns
      port: 53
      protocol: UDP
    - name: dns-tcp
      port: 53
      protocol: TCP
  EOF
  

• 这里的 clusterIP 需与 kubelet 配置文件中的 clusterDNS 一致

---

部署到 kubernetes 中

• 使用 kubectl 直接应用

  kubectl apply -f 0.coredns-sa.yml
  kubectl apply -f 1.coredns-rbac.yml
  kubectl apply -f 2.coredns-configmap.yml
  kubectl apply -f 3.coredns-deployment.yml
  kubectl apply -f 4.coredns-service.yml
  

---

查看 coredns 状态

• 查看 service 状态

  kubectl get svc -n kube-system
  

  • service 地址应是之前指定的 clusterIP(10.10.9.2)

• 查看 coredns pods 状态

  kubectl get pods -n kube-system -l k8s-app=coredns
  

  • 正常时都是 running

• 查看 coredns pods 输出

  kubectl logs <pod_name> -n kube-system
  

  • 正常输出类似如下

    .:53
    2019/04/14 12:20:09 [INFO] CoreDNS-1.2.2
    2019/04/14 12:20:09 [INFO] linux/amd64, go1.11, eb51e8b
    CoreDNS-1.2.2
    linux/amd64, go1.11, eb51e8b
    

---

来源：oschina

链接：https://my.oschina.net/u/2298475/blog/3036742