如何部署coredns

CoreDNS 其实就是一个 DNS 服务，而 DNS 作为一种常见的服务发现手段，所以很多开源项目以及工程师都会使用 CoreDNS 为集群提供服务发现的功能，Kubernetes 就在集群中使用 CoreDNS 解决服务发现的问题。

coredns镜像版本：v1.6.6
以下是部署所需YAML 文件， 主要修改位置：Service中的clusterIP
YAML文件来源：
https://github.com/coredns/deployment/tree/master/kubernetes      
coredns.yaml.sed  修改而来。

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 - 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 --- apiVersion: v1 kind: ConfigMap metadata:  name: coredns  namespace: kube-system data:  Corefile: |    .:53 {        errors        health {          lameduck 5s        }        ready        kubernetes cluster.local in-addr.arpa ip6.arpa {          fallthrough in-addr.arpa ip6.arpa        }        prometheus :9153        forward . /etc/resolv.conf        cache 30        loop        reload        loadbalance    } --- 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 --- 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: 10.110.0.2  ports:  - name: dns    port: 53    protocol: UDP  - name: dns-tcp    port: 53    protocol: TCP  - name: metrics    port: 9153    protocol: TCP