09-1.部署 coredns 插件

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 zhangjun-k8s01 节点上执行；
kuberntes 自带插件的 manifests yaml 文件使用 gcr.io 的 docker registry，国内被墙，需要手动替换为其它 registry 地址（本文档未替换）；
可以从微软中国提供的 gcr.io 免费代理下载被墙的镜像；

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。

cd /opt/k8s/work/kubernetes/
tar -xzvf kubernetes-src.tar.gz

coredns 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-5b969f4c88-jb6jg   1/1     Running   0          61m
NAME               TYPE        CLUSTER-IP   EXTERNAL-IP   PORT(S)                  AGE
service/kube-dns   ClusterIP   10.254.0.2   <none>        53/UDP,53/TCP,9153/TCP   61m
NAME                      READY   UP-TO-DATE   AVAILABLE   AGE
deployment.apps/coredns   1/1     1            1           61m
NAME                                 DESIRED   CURRENT   READY   AGE
replicaset.apps/coredns-5b969f4c88   1         1         1       61m

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   10.254.38.37    <none>        80/TCP                   7s

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 get pods -lapp=dnsutils-ds
NAME                READY   STATUS    RESTARTS   AGE
dnsutils-ds-57xqd   1/1     Running   0          101s
dnsutils-ds-5fdmb   1/1     Running   0          101s
dnsutils-ds-9twwf   1/1     Running   0          101s

$ kubectl -it exec dnsutils-ds-57xqd  bash
root@dnsutils-ds-57xqd:/# cat /etc/resolv.conf
nameserver 10.254.0.2
search default.svc.cluster.local svc.cluster.local cluster.local onecloud.local
options ndots:5

$ kubectl exec dnsutils-ds-57xqd 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-57xqd 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: 61.135.169.121
Name:   www.a.shifen.com
Address: 61.135.169.125

$ kubectl exec dnsutils-ds-57xqd nslookup my-nginx
Server:         10.254.0.2
Address:        10.254.0.2#53
Name:   my-nginx.default.svc.cluster.local
Address: 10.254.38.37

$ kubectl exec dnsutils-ds-57xqd nslookup kube-dns.kube-system.svc.cluster
Server:         10.254.0.2
Address:        10.254.0.2#53
** server can't find kube-dns.kube-system.svc.cluster: SERVFAIL
command terminated with exit code 1

$ kubectl exec dnsutils-ds-57xqd 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-57xqd 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

$ kubectl exec dnsutils-ds-57xqd 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

09-1.dns插件

09-1.部署 coredns 插件

修改配置文件

创建 coredns

检查 coredns 功能

参考