Kubernetes提供的DNS由以下三個組件組成：
1． etcd：DNS存儲
2． kube2sky：將kubernetes master中的service（服務）註冊到etcd
3． skyDNS：提供DNS域名解析服務 這三個組件以pod的方式啟動和運行

添加組件鏡像etcd，kube2sky，skydns，exechealthz

docker pull docker.gaoxiaobang.com/kubernetes/etcd-amd64:2.2.1

docker pull docker.gaoxiaobang.com/kubernetes/kube2sky:1.14

docker pull docker.gaoxiaobang.com/kubernetes/skydns:2015-10-13-8c72f8c

docker pull docker.gaoxiaobang.com/kubernetes/exechealthz:1.0

docker tag docker.gaoxiaobang.com/kubernetes/skydns:2015-10-13-8c72f8c 192.168.1.5:5000/skydns:2015-10-13-8c72f8c

docker tag docker.gaoxiaobang.com/kubernetes/kube2sky:1.14 192.168.1.5:5000/kube2sky:1.14

docker tag docker.gaoxiaobang.com/kubernetes/etcd-amd64:2.2.1 192.168.1.5:5000/etcd-amd64:2.2.1

docker tag docker.gaoxiaobang.com/kubernetes/exechealthz:1.0 192.168.1.5:5000/exechealthz:1.0

docker push 192.168.1.5:5000/skydns:2015-10-13-8c72f8c

docker push 192.168.1.5:5000/kube2sky:1.14

docker push 192.168.1.5:5000/etcd-amd64:2.2.1

docker push 192.168.1.5:5000/exechealthz:1.0

docker pull busybox #用作命令工具

docker tag docker.io/busybox 192.168.1.5:5000/busybox

docker push 192.168.1.5:5000/busybox

創建yaml文件,skydns-rc.yaml,skydns-svc.yaml,busybox.yaml

cd /home/dns

==============================================================================

vi skydns-rc.yaml

apiVersion: v1
kind: ReplicationController
metadata:
  name: kube-dns-v9
  namespace: default
  labels:
    k8s-app: kube-dns
    version: v9
    kubernetes.io/cluster-service: "true"
spec:
  replicas: 1
  selector:
    k8s-app: kube-dns
    version: v9
  template:
    metadata:
      labels:
        k8s-app: kube-dns
        version: v9
        kubernetes.io/cluster-service: "true"
    spec:
      containers:
      - name: etcd
        image: 192.168.1.5:5000/etcd-amd64:2.2.1
        imagePullPolicy: IfNotPresent
        resources:
          limits:
            cpu: 100m
            memory: 50Mi
        command:
        - /usr/local/bin/etcd
       # - --privileged=true
        - -data-dir
        - /var/etcd/data
        - -listen-client-urls
        - http://127.0.0.1:2379,http://127.0.0.1:4001
        - -advertise-client-urls
        - http://127.0.0.1:2379,http://127.0.0.1:4001
        - -initial-cluster-token
        - skydns-etcd
        volumeMounts:
        - mountPath: /var/etcd/data
          name: etcd-storage
      - name: kube2sky
        #image: gcr.io/google_containers/kube2sky:1.11
        image: 192.168.1.5:5000/kube2sky:1.14
        imagePullPolicy: IfNotPresent
        resources:
          limits:
            cpu: 100m
            memory: 50Mi
        livenessProbe:
          httpGet:
            path: /healthz
            port: 8080
            scheme: HTTP
          initialDelaySeconds: 60
          timeoutSeconds: 5
          successThreshold: 1
          failureThreshold: 5
        readinessProbe:
          httpGet:
            path: /readiness
            port: 8081
            scheme: HTTP
          initialDelaySeconds: 30
          timeoutSeconds: 5
        args:
        # command = "/kube2sky"
       # - -etcd-server=http://127.0.0.1:4001
        #- -kube_master_url=http://172.27.8.210:8080
        - --kube-master-url=http://192.168.1.5:8080
        - --domain=atomic.io
      - name: skydns
        #image: gcr.io/google_containers/skydns:2015-03-11-001
        image: 192.168.1.5:5000/skydns:2015-10-13-8c72f8c
        imagePullPolicy: IfNotPresent
        resources:
          limits:
            cpu: 100m
            memory: 50Mi
        args:
        # command = "/skydns"
        - -machines=http://127.0.0.1:2379
        - -addr=0.0.0.0:53
        - -ns-rotate=false
        - -domain=atomic.io
        ports:
        - containerPort: 53
          name: dns
          protocol: UDP
        - containerPort: 53
          name: dns-tcp
          protocol: TCP
        livenessProbe:
          httpGet:
            path: /healthz
            port: 8080
            scheme: HTTP
          initialDelaySeconds: 30
          timeoutSeconds: 5
        readinessProbe:
          httpGet:
            path: /healthz
            port: 8080
            scheme: HTTP
          initialDelaySeconds: 1
          timeoutSeconds: 5
      - name: healthz
        #image: gcr.io/google_containers/exechealthz:1.0
        image: 192.168.1.5:5000/exechealthz:1.0
        imagePullPolicy: IfNotPresent
        resources:
          limits:
            cpu: 10m
            memory: 20Mi
        args:
        - -cmd=nslookup kubernetes.default.svc.atomic.io 127.0.0.1 >/dev/null
        - -port=8080
        ports:
        - containerPort: 8080
          protocol: TCP
      volumes:
      - name: etcd-storage
        emptyDir: {}
      dnsPolicy: Default

需要註意修改下面一些內容

1，對應的四個鏡像地址

image: 192.168.1.5:5000/etcd-amd64:2.2.1

image: 192.168.1.5:5000/kube2sky:1.14

image: 192.168.1.5:5000/skydns:2015-10-13-8c72f8c

image: 192.168.1.5:5000/exechealthz:1.0

2，master和domain地址

- --kube-master-url=http://192.168.1.5:8080 #集群master的訪問地址

- --domain=atomic.io #flannel網絡定義的domain

3，namespace的定義

namespace: default

args:

- -cmd=nslookup kubernetes.default.svc.atomic.io 127.0.0.1 >/dev/null #註意namespace和flannel網絡名

4，skydns的啟動參數-addr=0.0.0.0:53表示使用本機TCP和UDP的53端口提供服務

5,鏡像服務的127.0.0.1地址不要隨意改，保持原狀，保證一個pod內的不同dns應用服務的調用地址一致

6，目錄掛載保持一致對應

- -data-dir

- /var/etcd/data

volumeMounts:

- mountPath: /var/etcd/data

=============================================================================

vi skydns-svc.yaml

apiVersion: v1
kind: Service
metadata:
  name: kube-dns
  namespace: default
  labels:
    k8s-app: kube-dns
    kubernetes.io/cluster-service: "true"
    kubernetes.io/name: "KubeDNS"
spec:
  selector:
    k8s-app: kube-dns
  clusterIP:  10.254.10.20
  ports:
  - name: dns
    port: 53
    protocol: UDP
  - name: dns-tcp
    port: 53
    protocol: TCP

這個文件需要註意的是

clusterIP: 10.254.10.20

這個IP是在/etc/kubernetes/kubelet中定義的，

KUBELET_ARGS="--cluster-dns=10.254.10.20 --cluster-domain=atomic.io"

每個node上的/etc/kubernetes/kubelet啟動參數
--cluster_dns=10.254.10.20 為dns服務的clusterIP
--cluster_domain=atomic.io 為dns服務中設置的域名

如果參數不一致就修改重啟該kubelet

vi busybox.yaml

apiVersion: v1
kind: Pod
metadata:
  name: busybox
  namespace: default
spec:
  containers:
    - image: 192.168.1.5:5000/busybox
      command:
        - sleep
        - "3600"
      imagePullPolicy: IfNotPresent
      name: busybox
  restartPolicy: Always

創建好文件後，用命令執行創建

kubectl create -f skydns-rc.yaml

kubectl create -f skydns-svc.yaml

kubectl create -f busybox.yaml

kubectl get pods --all-namespaces -o wide

[root@k8s-master dns]# kubectl get pods --all-namespaces -o wide 
NAMESPACE     NAME                       READY       STATUS    RESTARTS      AGE        IP          NODE
default        busybox                    1/1        Running   5          5h        172.17.85.4   k8s-node-1
default       kube-dns-v9-hnp4m               4/4       Running   0          5h        172.17.32.5   192.168.1.5
kube-system   heapster-3919175978-gd82j           1/1       Running   0          12h       172.17.85.3   k8s-node-1
kube-system   kubernetes-dashboard-3155532917-wdq38   1/1       Running   0          12h       172.17.85.2   k8s-node-1
kube-system   monitoring-grafana-3994812335-wv9dh    1/1       Running   0          12h       172.17.32.2   192.168.1.5
kube-system   monitoring-influxdb-265709471-xv170    1/1       Running   0          12h       172.17.32.3   192.168.1.5

執行dns檢測命令（busybox是一個命令工具）

[root@k8s-master dns]# kubectl exec busybox -- nslookup kubernetes

Server: 10.254.10.20

Address 1: 10.254.10.20

Name: kubernetes

Address 1: 10.254.0.1

如果某個service屬於自定義的命名空間，那麽在進行service查找時，需要帶上namespace的名字

[root@k8s-master dns]# kubectl exec busybox -- nslookup kubernetes-dashboard.kube-system

Server: 10.254.10.20

Address 1: 10.254.10.20

Name: kubernetes-dashboard.kube-system

Address 1: 10.254.132.77

用命令查看svc，對應下域名解析正確

[root@k8s-master dns]# kubectl get svc --all-namespaces -o wide

NAMESPACE NAME CLUSTER-IP EXTERNAL-IP PORT(S) AGE SELECTOR

default kube-dns 10.254.10.20 <none> 53/UDP,53/TCP 5h k8s-app=kube-dns

default kubernetes 10.254.0.1 <none> 443/TCP 8d <none>

kube-system heapster 10.254.189.98 <none> 80/TCP 12h k8s-app=heapster

kube-system kubernetes-dashboard 10.254.132.77 <nodes> 80:30699/TCP 12h app=kubernetes-dashboard

kube-system monitoring-grafana 10.254.178.155 <none> 80/TCP 12h k8s-app=grafana

kube-system monitoring-influxdb 10.254.59.144 <none> 8086/TCP 12h k8s-app=influxdb

k8s--DNS域名服務