五、搭建kube-dns

1. 简介

  kube-dns用来为kubernetes service分配子域名，在集群中可以通过名称访问service。通常kube-dns会为service赋予一个名为“service名称.namespace.svc.cluster.local”的A记录，用来解析service的cluster ip。

2.修改Node配置文件

2.1 修改kubelet配置文件

vim /etc/kubernetes/kubelet

KUBELET_ADDRESS="--address=0.0.0.0"
#KUBELET_HOSTNAME="--hostname-override=127.0.0.1"
KUBELET_HOSTNAME="--hostname-override=k8s-node-1"
KUBELET_API_SERVER="--api-servers=http://k8s-master:8080"
KUBELET_POD_INFRA_CONTAINER="--pod-infra-container-image=registry.access.redhat.com/rhel7/pod-infrastructure:latest"
KUBELET_ARGS="--cluster-dns=172.16.1.100 --cluster-domain=cluster.local. --allow-privileged=true"    #设置dns ip

2.2 重启kubelet服务

systemctl restart kubelet.service

3.创建kube-dns所需配置文件

3.1 创建kube-dns-rc文件

vim kube-dns-rc.yaml

apiVersion: v1
kind: ReplicationController
metadata:
  name: kube-dns-v20
  namespace: kube-system
  labels:
    k8s-app: kube-dns
    version: v20
    kubernetes.io/cluster-service: "true"
spec:
  replicas: 1
  selector:
    k8s-app: kube-dns
    version: v20
  template:
    metadata:
      labels:
        k8s-app: kube-dns
        version: v20
      annotations:
        scheduler.alpha.kubernetes.io/critical-pod: ''
        scheduler.alpha.kubernetes.io/tolerations: '[{"key":"CriticalAddonsOnly", "operator":"Exists"}]'
    spec:
      containers:
      - name: kubedns
        image: gcr.io/google_containers/kubedns-amd64:1.8
        imagePullPolicy: IfNotPresent
        resources:
          limits:
            memory: 170Mi
          requests:
            cpu: 100m
            memory: 70Mi
        livenessProbe:
          httpGet:
            path: /healthz-kubedns
            port: 8080
            scheme: HTTP
          initialDelaySeconds: 60
          timeoutSeconds: 5
          successThreshold: 1
          failureThreshold: 5
        readinessProbe:
          httpGet:
            path: /readiness
            port: 8081
            scheme: HTTP
          initialDelaySeconds: 3
          timeoutSeconds: 5
        args:
        - --domain=cluster.local.
        - --dns-port=10053
        - --kube-master-url=http://10.0.251.148:8080
        ports:
        - containerPort: 10053
          name: dns-local
          protocol: UDP
        - containerPort: 10053
          name: dns-tcp-local
          protocol: TCP
      - name: dnsmasq
        image: gcr.io/google_containers/kube-dnsmasq-amd64:1.4.1
        imagePullPolicy: IfNotPresent
        livenessProbe:
          httpGet:
            path: /healthz-dnsmasq
            port: 8080
            scheme: HTTP
          initialDelaySeconds: 60
          timeoutSeconds: 5
          successThreshold: 1
          failureThreshold: 5
        args:
        - --cache-size=1000
        - --no-resolv
        - --server=127.0.0.1#10053
        - --log-facility=-
        ports:
        - containerPort: 53
          name: dns
          protocol: UDP
        - containerPort: 53
          name: dns-tcp
          protocol: TCP
      - name: healthz
        image: gcr.io/google_containers/exechealthz-amd64:1.2
        imagePullPolicy: IfNotPresent
        resources:
          limits:
            memory: 50Mi
          requests:
            cpu: 10m
            memory: 50Mi
        args:
        - --cmd=nslookup kubernetes.default.svc.cluster.local. 127.0.0.1 >/dev/null
        - --url=/healthz-dnsmasq
        - --cmd=nslookup kubernetes.default.svc.cluster.local. 127.0.0.1:10053 >/dev/null
        - --url=/healthz-kubedns
        - --port=8080
        - --quiet
        ports:
        - containerPort: 8080
          protocol: TCP
      dnsPolicy: Default

  此rc配置文件需要确定的是Kubernetes Master地址填写正确，以及image可以正常pull使用。

3.2 创建kube-dns-svc.yaml

vim kube-dns-svc.yaml

apiVersion: v1
kind: Service
metadata:
  name: kube-dns
  namespace: kube-system
  labels:
    k8s-app: kube-dns
    kubernetes.io/cluster-service: "true"
    kubernetes.io/name: "KubeDNS"
spec:
  selector:
    k8s-app: kube-dns
  clusterIP: 172.16.1.100    #设置dns服务地址
  ports:
  - name: dns
    port: 53
    protocol: UDP
  - name: dns-tcp
    port: 53
    protocol: TCP

3.3 下载docker镜像

docker pull gcr.io/google_containers/kubedns-amd64:1.8

docker pull gcr.io/google_containers/kube-dnsmasq-amd64:1.4.1

docker pull gcr.io/google_containers/exechealthz-amd64:1.2

  在所有Node上准备好所需镜像，可以提升Kubernetes创建Pod的速度。

3.4 启动RC和SVC

kubectl create -f kube-dns-rc.yaml

kubectl create -f kube-dns-svc.yaml

3.5 验证dns-pod启动是否成功

kubectl get -o wide

&验证kube-dns pod启动没问题后，kube-dns及可使用。至此Kubernetes环境构建完成，可以先上使用，接下来就需要我们自己编写配置文件了。