k8s动态配置/etc/hosts

###使用命令行修改hosts，完事后保存退出，立即生效
kubectl  edit configmap  coredns  -n  kube-system

　

# Please edit the object below. Lines beginning with a '#' will be ignored,
# and an empty file will abort the edit. If an error occurs while saving this file will be
# reopened with the relevant failures.
#
# configmaps "coredns" was not valid:
# * <nil>: Invalid value: "The edited file failed validation": [yaml: line 16: found a tab character where an indentation space is expected, invalid character 'a' looking for beginning of value]
#
apiVersion: v1
data:
  Corefile: |
    .:53 {
        errors
        health {
           lameduck 15s
        }
        ready

        kubernetes apicloud.com in-addr.arpa ip6.arpa {

          pods verified
          fallthrough in-addr.arpa ip6.arpa
        }
        #下面hosts字段为新增
        hosts {
            47.95.x.120 pre.xxx.com
            47.95.x.120 www.xxx.com
            fallthrough
        }
        prometheus :9153
        forward . /etc/resolv.conf
        cache 30
        loop
        reload
        loadbalance
    }
kind: ConfigMap
metadata:
  annotations:
    kubectl.kubernetes.io/last-applied-configuration: |
      {"apiVersion":"v1","data":{"Corefile":".:53 {\n    errors\n    health {\n       lameduck 15s\n    }\n    ready\n\n    kubernetes xxxcloud.com in-addr.arpa ip6.arpa {\n\n      pods verified\n      fallthrough in-addr.arpa ip6.arpa\n    }\n    prometheus :9153\n    forward . /etc/resolv.conf\n    cache 30\n    loop\n    reload\n    loadbalance\n}\n"},"kind":"ConfigMap","metadata":{"annotations":{},"name":"coredns","namespace":"kube-system"}}
  creationTimestamp: "2021-08-07T10:20:37Z"
  name: coredns
  namespace: kube-system
  resourceVersion: "960"
  uid: 292160fc-e4b6-417f-876a-57d02932352a

　　

 参考：https://help.aliyun.com/document_detail/188179.html?spm=5176.smartservice_service_chat.0.0.76e53f1bOJhMwX

解决的问题：

　　1.内网体系测试使用；

　　2.宿主机和本地hosts自定义解析；

　　3.容器依然读取公共dns解析的情况下，配置上述信息可以与本地host解析同步

终极解决目标

　　　设置pod内DNS解析规则跟随node结点：  dnsPolicy:Default  

参考自：https://help.aliyun.com/document_detail/188179.html?spm=5176.smartservice_service_chat.0.0.76e5709aYtcZMI

集群dnsPolicy配置和场景说明

ACK支持通过dnsPolicy字段为每个Pod配置不同的DNS策略。目前ACK集群支持四种策略：

• ClusterFirst：通过CoreDNS来做域名解析，Pod内/etc/resolv.conf配置的DNS服务地址是集群DNS服务的kube-dns地址。该策略是集群工作负载的默认策略。
• None：忽略集群DNS策略，需要您提供dnsConfig字段来指定DNS配置信息。
• Default：Pod直接继承集群节点的域名解析配置。即在ACK集群直接使用ECS的/etc/resolv.conf文件（文件内配置的是阿里云DNS服务）。
• ClusterFirstWithHostNet：强制在hostNetWork网络模式下使用ClusterFirst策略（默认使用Default策略）。