十一、部署coredns

1、coredns.yaml

[root@k8s-master01 yaml]# cat coredns.yaml 
# Warning: This is a file generated from the base underscore template file: coredns.yaml.base

apiVersion: v1
kind: ServiceAccount
metadata:
  name: coredns
  namespace: kube-system
  labels:
      kubernetes.io/cluster-service: "true"
      addonmanager.kubernetes.io/mode: Reconcile
---
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
---
apiVersion: v1
kind: ConfigMap
metadata:
  name: coredns
  namespace: kube-system
  labels:
      addonmanager.kubernetes.io/mode: EnsureExists
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: apps/v1
kind: Deployment
metadata:
  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:
      serviceAccountName: coredns
      tolerations:
        - key: node-role.kubernetes.io/master
          effect: NoSchedule
        - key: "CriticalAddonsOnly"
          operator: "Exists"
      containers:
      - name: coredns
        image: lizhenliang/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
        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
        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: 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"
    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

2、部署

[root@k8s-master01 yaml]# kubectl apply -f coredns.yaml 
serviceaccount/coredns created
clusterrole.rbac.authorization.k8s.io/system:coredns created
clusterrolebinding.rbac.authorization.k8s.io/system:coredns created
configmap/coredns created
deployment.apps/coredns created
service/kube-dns created

[root@k8s-master01 yaml]# kubectl get pods -n kube-system
NAME                          READY   STATUS    RESTARTS   AGE
coredns-6d8cfdd59d-vk724      1/1     Running   0          28s

3、测试dns

下载一个busybox镜像进行测试

[root@k8s-master01 yaml]# cat busybox.yaml 
apiVersion: v1
kind: Pod
metadata: 
    name: busybox
    namespace: default
spec:
    containers:
      - image: busybox:1.28.4
        command:
          - sleep
          - "3600"
        imagePullPolicy: IfNotPresent
        name: busybox
    restartPolicy: Always


[root@k8s-master01 yaml]# kubectl apply -f busybox.yaml 
pod/busybox created
[root@k8s-master01 yaml]# kubectl get pods
NAME      READY   STATUS    RESTARTS   AGE
busybox   1/1     Running   0          6s

创建一个nginx镜像，名称为web

root@k8s-master01 yaml]# kubectl create deployment web --image=nginx
deployment.apps/web created
[root@k8s-master01 yaml]# kubectl expose deployment web --port=80 --type=NodePort
service/web exposed

[root@k8s-master01 yaml]# kubectl get pods
NAME                  READY   STATUS    RESTARTS   AGE
busybox               1/1     Running   0          6m13s
web-d86c95cc9-9zxm8   1/1     Running   0          93s

[root@k8s-master01 yaml]# kubectl get svc
NAME         TYPE        CLUSTER-IP   EXTERNAL-IP   PORT(S)        AGE
kubernetes   ClusterIP   10.0.0.1     <none>        443/TCP        23h
web          NodePort    10.0.0.250   <none>        80:32241/TCP   5m18s

进入busybox测试

[root@k8s-master01 yaml]# kubectl exec -it busybox sh
/ # ping web
PING web (10.0.0.250): 56 data bytes
64 bytes from 10.0.0.250: seq=0 ttl=64 time=0.102 ms
64 bytes from 10.0.0.250: seq=1 ttl=64 time=0.158 ms
64 bytes from 10.0.0.250: seq=2 ttl=64 time=0.181 ms
64 bytes from 10.0.0.250: seq=3 ttl=64 time=0.170 ms
/ # nslookup web
Server:    10.0.0.2
Address 1: 10.0.0.2 kube-dns.kube-system.svc.cluster.local

Name:      web
Address 1: 10.0.0.250 web.default.svc.cluster.local