K8S-Demo集群实践：部署集群CoreDNS

K8S-Demo集群实践：部署集群CoreDNS

• 一、下载CoreDNS
• 二、修改部署脚本 deploy.sh
• 三、部署CoreDNS并测试
• 四、问题
• 参考

一、下载CoreDNS

[[email protected] ~]# cd /opt/install
[[email protected] install]# mkdir coredns
[[email protected] install]# cd coredns
[[email protected] coredns]# git clone https://github.com/coredns/deployment.git
[[email protected] coredns]# cd ./deployment/kubernetes

二、修改部署脚本 deploy.sh

• 找到 CLUSTER_DNS_IP=$(kubectl get service --namespace kube-system kube-dns -o jsonpath="{.spec.clusterIP}")
• 修改为：CLUSTER_DNS_IP=10.8.0.2

三、部署CoreDNS并测试

1、生成coredns.yaml并部署

[[email protected] ~]# cd /opt/install/coredns
[[email protected] coredns]# ./deploy.sh > coredns.yaml
[[email protected] coredns]# kubectl apply -f coredns.yaml

• yaml文件中的镜像 是1.8.0版本，测试有问题，修改为1.7.0后测试成功
• 在Corefile部分添加了宿主机的解析

... ... ... ...
        kubernetes cluster.demo in-addr.arpa ip6.arpa {
          fallthrough in-addr.arpa ip6.arpa
        }
        hosts {
          192.168.66.10    master1
          192.168.66.11    master2
          192.168.66.12    master3
          192.168.66.13    node1
          192.168.66.14    node2
          192.168.66.15    node3
          192.168.66.106   harbor
          192.168.66.106   harbor.demo
        }
        prometheus :9153
... ... ... ...

2、查看服务状态

[[email protected] ~]# kubectl get rs,deploy,svc,pods -n kube-system| grep dns
replicaset.apps/coredns-7f44d46d8d                   2         2         2       23d
deployment.apps/coredns                   2/2     2            2           23d
service/kube-dns         ClusterIP   10.8.0.2      <none>        53/UDP,53/TCP,9153/TCP         23d
pod/coredns-7f44d46d8d-9btdv                   1/1     Running   2          7d
pod/coredns-7f44d46d8d-dc4b9                   1/1     Running   2          7d

3、创建一个 busybox Pod

[[email protected] ~]# cd /opt/install/coredns
[[email protected] coredns]# vim busybox.yaml
apiVersion: v1
kind: Pod
metadata:
  name: busybox
  namespace: default
spec:
  containers:
  - name: busybox
    image: busybox:1.28.3
    command:
      - sleep
      - "3600"
    imagePullPolicy: IfNotPresent
  restartPolicy: Always
[[email protected] coredns]# kubectl apply -f busybox.yaml

4、进入busybox容器测试CoreDNS，执行nslookup

[[email protected] ~]# kubectl exec -it busybox /bin/sh
/ # nslookup kubernetes
Server:    10.8.0.2
Address 1: 10.8.0.2 kube-dns.kube-system.svc.cluster.demo

Name:      kubernetes
Address 1: 10.8.0.1 kubernetes.default.svc.cluster.demo
/ # nslookup metrics-server.kube-system.svc.cluster.demo
Server:    10.8.0.2
Address 1: 10.8.0.2 kube-dns.kube-system.svc.cluster.demo

Name:      metrics-server.kube-system.svc.cluster.demo
Address 1: 10.8.20.170 metrics-server.kube-system.svc.cluster.demo
/ # nslookup kube-dns.kube-system.svc.cluster.demo
Server:    10.8.0.2
Address 1: 10.8.0.2 kube-dns.kube-system.svc.cluster.demo

Name:      kube-dns.kube-system.svc.cluster.demo
Address 1: 10.8.0.2 kube-dns.kube-system.svc.cluster.demo
/ # nslookup 192.168.66.12
Server:    10.8.0.2
Address 1: 10.8.0.2 kube-dns.kube-system.svc.cluster.demo

Name:      192.168.66.12
Address 1: 192.168.66.12 192-168-66-12.kubernetes.default.svc.cluster.demo
/ # nslookup 10.8.234.157
Server:    10.8.0.2
Address 1: 10.8.0.2 kube-dns.kube-system.svc.cluster.demo

Name:      10.8.234.157
Address 1: 10.8.234.157 kubernetes-dashboard.kubernetes-dashboard.svc.cluster.demo

四、问题

• 问题：./deploy.sh:行61: jq: 未找到命令
• 解决方法

[[email protected] ~]# yum install epel-release
[[email protected] ~]# yum list jq
[[email protected] ~]# yum install jq

参考

• KubeDNS对比CoreDNS https://zhuanlan.zhihu.com/p/80141656
• https://coredns.io/plugins/loop/#troubleshooting

---

• 先用起来，通过操作实践认识k8s，积累多了自然就理解了
• 把理解的知识分享出来，自造福田，自得福缘
• 追求简单，容易使人理解，知识的上下文也是知识的一部分，例如版本，时间等
• 欢迎留言交流，也可以提出问题，一般在周末回复和完善文档
• [email protected] 2021-1-22