"nslookup： read：连接拒绝"从库伯内特斯（K8S）集群中的吊舱内（DNS问题）

Question

我在基于Centos 7的AWS ec2上自定义安装了k8s群集，其中有1个主节点和1个节点。当调用例如nslookup google.com时，它在节点吊舱内部使用核心DNS（吊舱运行正常，日志中没有错误）。输出为nslookup:write to'10.96.0.10'：连接被拒绝；；连接超时；无法访问任何服务器

例如，在pod内部pingping 8.8.8.8可以正常工作：

PING 8.8.8.8 (8.8.8.8): 56 data bytes
64 bytes from 8.8.8.8: seq=0 ttl=50 time=1.330 ms

/etc/resolv.conf在一个Pod中，它看起来像：

nameserver 10.96.0.10
search default.svc.cluster.local svc.cluster.local cluster.local ec2.internal
options ndots:5

此命令在节点本身运行良好nslookup google.com：

Server:         172.31.0.2
Address:        172.31.0.2#53

Non-authoritative answer:
Name:   google.com
Address: 172.217.15.110
Name:   google.com
Address: 2607:f8b0:4004:801::200e

Kubelet配置kubectl获取配置映射Kubelet-config-1.17-n kube系统-o yaml返回

data:
  kubelet: |
    apiVersion: kubelet.config.k8s.io/v1beta1
    authentication:
      anonymous:
        enabled: false
      webhook:
        cacheTTL: 0s
        enabled: true
      x509:
        clientCAFile: /etc/kubernetes/pki/ca.crt
    authorization:
      mode: Webhook
      webhook:
        cacheAuthorizedTTL: 0s
        cacheUnauthorizedTTL: 0s
    clusterDNS:
    - 10.96.0.10
    clusterDomain: cluster.local
    cpuManagerReconcilePeriod: 0s
    evictionPressureTransitionPeriod: 0s
    fileCheckFrequency: 0s
    healthzBindAddress: 127.0.0.1
    healthzPort: 10248
    httpCheckFrequency: 0s
    imageMinimumGCAge: 0s
    kind: KubeletConfiguration
    nodeStatusReportFrequency: 0s
    nodeStatusUpdateFrequency: 0s
    rotateCertificates: true
    runtimeRequestTimeout: 0s
    staticPodPath: /etc/kubernetes/manifests
    streamingConnectionIdleTimeout: 0s
    syncFrequency: 0s
    volumeStatsAggPeriod: 0s
kind: ConfigMap

kube命名空间中的Podskubectl获取Pods-n kube系统如下所示：

coredns-6955765f44-qdbgx                                1/1     Running   6          11d
coredns-6955765f44-r4v7n                                1/1     Running   6          11d
etcd-ip-172-31-42-121.ec2.internal                      1/1     Running   7          11d
kube-apiserver-ip-172-31-42-121.ec2.internal            1/1     Running   7          11d
kube-controller-manager-ip-172-31-42-121.ec2.internal   1/1     Running   6          11d
kube-proxy-lrpd9                                        1/1     Running   6          11d
kube-proxy-z55cv                                        1/1     Running   6          11d
kube-scheduler-ip-172-31-42-121.ec2.internal            1/1     Running   6          11d
weave-net-bdn5n                                         2/2     Running   0          39h
weave-net-z7mks                                         2/2     Running   5          39h

从pod中，如果我执行ip路由，它将返回：

default via 10.32.0.1 dev eth0 
10.32.0.0/12 dev eth0 scope link  src 10.32.0.16 

来自master：

default via 172.31.32.1 dev eth0 
10.32.0.0/12 dev weave proto kernel scope link src 10.32.0.1 
172.17.0.0/16 dev docker0 proto kernel scope link src 172.17.0.1 
172.31.32.0/20 dev eth0 proto kernel scope link src 172.31.42.121 

从节点：

default via 172.31.32.1 dev eth0 
10.32.0.0/12 dev weave proto kernel scope link src 10.32.0.1 
172.17.0.0/16 dev docker0 proto kernel scope link src 172.17.0.1 
172.31.32.0/20 dev eth0 proto kernel scope link src 172.31.46.62 

CoreDNS configmapkubectl-n kube系统获取配置映射CoreDNS-oyaml是：

apiVersion: v1
data:
  Corefile: |
    .:53 {
        log
        errors
        health {
           lameduck 5s
        }
        ready
        kubernetes cluster.local in-addr.arpa ip6.arpa {
           pods insecure
           fallthrough in-addr.arpa ip6.arpa
           ttl 30
        }
        prometheus :9153
        forward . /etc/resolv.conf
        cache 30
        loop
        reload
        loadbalance
    }
kind: ConfigMap

那么为什么nslookup google.com不能在一个pod中工作呢？？

Answer 1

k8s集群的安装是错误的，一个可行的脚本应该包含正确的主IP和ec2虚拟机上的节点。

dev-kubernetes-master ansible_host=34.233.207.xxx private_ip=172.31.37.xx
dev-kubernetes-slave ansible_host=52.6.10.xxx private_ip=172.31.42.xxx

我已经用指定的正确的私有ip重新安装了集群（在根本没有私有ip之前），问题已经解决了。