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09-1.dns插件.md

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tags: addons, dns, coredns

09-1.部署 coredns 插件

注意：如果没有特殊指明，本文档的所有操作均在 m7-autocv-gpu01 节点上执行。

修改配置文件

将下载的 kubernetes-server-linux-amd64.tar.gz 解压后，再解压其中的 kubernetes-src.tar.gz 文件。

coredns 对应的目录是：cluster/addons/dns。

cd /opt/k8s/work/kubernetes/cluster/addons/dns/coredns
cp coredns.yaml.base coredns.yaml
source /opt/k8s/bin/environment.sh
sed -i -e "s/__PILLAR__DNS__DOMAIN__/${CLUSTER_DNS_DOMAIN}/" -e "s/__PILLAR__DNS__SERVER__/${CLUSTER_DNS_SVC_IP}/" coredns.yaml

创建 coredns

kubectl create -f coredns.yaml

检查 coredns 功能

$ kubectl get all -n kube-system
NAME                           READY     STATUS    RESTARTS   AGE
pod/coredns-77c989547b-6l6jr   1/1       Running   0          3m
pod/coredns-77c989547b-d9lts   1/1       Running   0          3m

NAME              TYPE        CLUSTER-IP   EXTERNAL-IP   PORT(S)         AGE
service/coredns   ClusterIP   10.254.0.2   <none>        53/UDP,53/TCP   3m

NAME                      DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGE
deployment.apps/coredns   2         2         2            2           3m

NAME                                 DESIRED   CURRENT   READY     AGE
replicaset.apps/coredns-77c989547b   2         2         2         3m

新建一个 Deployment

cd /opt/k8s/work
cat > my-nginx.yaml <<EOF
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: my-nginx
spec:
  replicas: 2
  template:
    metadata:
      labels:
        run: my-nginx
    spec:
      containers:
      - name: my-nginx
        image: nginx:1.7.9
        ports:
        - containerPort: 80
EOF
kubectl create -f my-nginx.yaml

Export 该 Deployment, 生成 my-nginx 服务：

$ kubectl expose deploy my-nginx
service "my-nginx" exposed

$ kubectl get services --all-namespaces |grep my-nginx
default       my-nginx      ClusterIP   10.254.92.83    <none>        80/TCP          6s

创建另一个 Pod，查看 /etc/resolv.conf 是否包含 kubelet 配置的 --cluster-dns 和 --cluster-domain，是否能够将服务 my-nginx 解析到上面显示的 Cluster IP 10.254.242.255

cd /opt/k8s/work
cat > dnsutils-ds.yml <<EOF
apiVersion: v1
kind: Service
metadata:
  name: dnsutils-ds
  labels:
    app: dnsutils-ds
spec:
  type: NodePort
  selector:
    app: dnsutils-ds
  ports:
  - name: http
    port: 80
    targetPort: 80
---
apiVersion: extensions/v1beta1
kind: DaemonSet
metadata:
  name: dnsutils-ds
  labels:
    addonmanager.kubernetes.io/mode: Reconcile
spec:
  template:
    metadata:
      labels:
        app: dnsutils-ds
    spec:
      containers:
      - name: my-dnsutils
        image: tutum/dnsutils:latest
        command:
          - sleep
          - "3600"
        ports:
        - containerPort: 80
EOF
kubectl create -f dnsutils-ds.yml
$ kubectl exec dnsutils-ds-c8kcw nslookup kubernetes
Server:         10.254.0.2
Address:        10.254.0.2#53

Name:   kubernetes.default.svc.cluster.local
Address: 10.254.0.1

$ kubectl exec dnsutils-ds-c8kcw nslookup www.baidu.com  # 解析外部域名时，需要以 . 结尾
Server:         10.254.0.2
Address:        10.254.0.2#53

Non-authoritative answer:
*** Can't find www.baidu.com: No answer

$ kubectl exec dnsutils-ds-c8kcw nslookup www.baidu.com.
Server:         10.254.0.2
Address:        10.254.0.2#53

Non-authoritative answer:
www.baidu.com   canonical name = www.a.shifen.com.
Name:   www.a.shifen.com
Address: 61.135.169.125
Name:   www.a.shifen.com
Address: 61.135.169.121

$ kubectl exec dnsutils-ds-c8kcw nslookup my-nginx
Server:         10.254.0.2
Address:        10.254.0.2#53

Name:   my-nginx.default.svc.cluster.local
Address: 10.254.229.163

$ kubectl exec dnsutils-ds-c8kcw nslookup kube-dns.kube-system.svc.cluster
Server:         10.254.0.2
Address:        10.254.0.2#53

Non-authoritative answer:
*** Can't find kube-dns.kube-system.svc.cluster: No answer

$ kubectl exec dnsutils-ds-c8kcw nslookup kube-dns.kube-system.svc
Server:         10.254.0.2
Address:        10.254.0.2#53

Name:   kube-dns.kube-system.svc.cluster.local
Address: 10.254.0.2

$ kubectl exec dnsutils-ds-c8kcw nslookup kube-dns.kube-system.svc.cluster.local
Server:         10.254.0.2
Address:        10.254.0.2#53

Non-authoritative answer:
*** Can't find kube-dns.kube-system.svc.cluster.local: No answer

$ kubectl exec dnsutils-ds-c8kcw nslookup kube-dns.kube-system.svc.cluster.local.
Server:         10.254.0.2
Address:        10.254.0.2#53

Name:   kube-dns.kube-system.svc.cluster.local
Address: 10.254.0.2

参考

  1. https://community.infoblox.com/t5/Community-Blog/CoreDNS-for-Kubernetes-Service-Discovery/ba-p/8187
  2. https://coredns.io/2017/03/01/coredns-for-kubernetes-service-discovery-take-2/
  3. https://www.cnblogs.com/boshen-hzb/p/7511432.html
  4. https://github.com/kubernetes/kubernetes/tree/master/cluster/addons/dns