环境

生成 service account 文件

  • 创建 0.coredns-sa.yml 
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    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 
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    curl > 1.coredns-rbac.yml <<EOF
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
- apiGroups:
  - ""
  resources:
  - nodes
  verbs:
  - get
---
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
EOF

生成 configmap 文件

  • 创建 2.coredns-configmap.yml 
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    cat > 2.coredns-configmap.yml <<EOF
apiVersion: v1
kind: ConfigMap
metadata:
  name: coredns
  namespace: kube-system
data:
  Corefile: |
    .:53 {
        errors
        health {
          lameduck 5s
        }
        ready
        kubernetes cluster.local 10.10.9.0/24 {
          fallthrough in-addr.arpa ip6.arpa
        }
        prometheus :9153
        forward . /etc/resolv.conf
        cache 30
        loop
        reload
        loadbalance
    }
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 
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    cat > 3.coredns-deployment.yml <<EOF
apiVersion: apps/v1
kind: Deployment
metadata:
  name: coredns
  namespace: kube-system
  labels:
    k8s-app: kube-dns
    kubernetes.io/name: "CoreDNS"
spec:
  # replicas: not specified here:
  # 1. Default is 1.
  # 2. 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
    spec:
      priorityClassName: system-cluster-critical
      serviceAccountName: coredns
      tolerations:
        - key: "CriticalAddonsOnly"
          operator: "Exists"
      nodeSelector:
        beta.kubernetes.io/os: linux
      affinity:
        podAntiAffinity:
          requiredDuringSchedulingIgnoredDuringExecution:
          - labelSelector:
              matchExpressions:
              - key: k8s-app
                operator: In
                values: ["kube-dns"]
            topologyKey: kubernetes.io/hostname
      containers:
      - name: coredns
        image: coredns/coredns:1.6.6
        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
        ports:
        - containerPort: 53
          name: dns
          protocol: UDP
        - containerPort: 53
          name: dns-tcp
          protocol: TCP
        - containerPort: 9153
          name: metrics
          protocol: TCP
        securityContext:
          allowPrivilegeEscalation: false
          capabilities:
            add:
            - NET_BIND_SERVICE
            drop:
            - all
          readOnlyRootFilesystem: true
        livenessProbe:
          httpGet:
            path: /health
            port: 8080
            scheme: HTTP
          initialDelaySeconds: 60
          timeoutSeconds: 5
          successThreshold: 1
          failureThreshold: 5
        readinessProbe:
          httpGet:
            path: /ready
            port: 8181
            scheme: HTTP
      dnsPolicy: Default
      volumes:
        - 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 
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    cat > 4.coredns-service.yml <<EOF
apiVersion: v1
kind: Service
metadata:
  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"
    kubernetes.io/name: "CoreDNS"
spec:
  selector:
    k8s-app: kube-dns
  clusterIP: 10.10.9.2
  ports:
  - name: dns
    port: 53
    protocol: UDP
  - name: dns-tcp
    port: 53
    protocol: TCP
  - name: metrics
    port: 9153
    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 
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    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

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    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

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    kubectl get pods -n kube-system
    • 正常时都是 running

  • 查看 coredns pods 输出

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    kubectl logs <pod_name> -n kube-system

参考