Kubernetes.default nslookup 无法从不同的命名空间解析

Question

我在解决 kubernetes.default.svc.cluster.local 时遇到问题来自外部default命名空间

我在每个命名空间上运行两个busybox:1.30 pod，并且名称成功地从default 解析。仅命名空间

    [admin@devsvr3 ~]$ kubectl exec -n default -ti busybox -- nslookup kubernetes
    Server:    10.96.0.10
    Address 1: 10.96.0.10 kube-dns.kube-system.svc.cluster.local
    Name:      kubernetes
    Address 1: 10.96.0.1 kubernetes.default.svc.cluster.local
    [admin@devsvr3 ~]$ kubectl exec -n namespace-dev -ti busybox -- nslookup kubernetes
    Server:         10.96.0.10
    Address:        10.96.0.10:53
    ** server can't find kubernetes.namespace-dev.svc.cluster.local: NXDOMAIN
    *** Can't find kubernetes.svc.cluster.local: No answer
    *** Can't find kubernetes.cluster.local: No answer
    *** Can't find kubernetes.namespace-dev.svc.cluster.local: No answer
    *** Can't find kubernetes.svc.cluster.local: No answer
    *** Can't find kubernetes.cluster.local: No answer
    [admin@devsvr3 ~]$ 

我在气隙环境中运行 CentOS 7 kubernetes 集群并使用 weave net CNI 插件，这是我的 CoreDNS 配置

    apiVersion: v1
    data:
      Corefile: |
        .:53 {
            log
            errors
            health
            kubernetes cluster.local in-addr.arpa ip6.arpa {
              pods insecure
              upstream
              fallthrough in-addr.arpa ip6.arpa
            }
            prometheus :9153
            proxy . /etc/resolv.conf
            cache 30
            reload
            loadbalance
        }
    kind: ConfigMap
    metadata:
      creationTimestamp: "2019-01-28T10:59:25Z"
      name: coredns
      namespace: kube-system
      resourceVersion: "1177652"
      selfLink: /api/v1/namespaces/kube-system/configmaps/coredns
      uid: c6b5ddae-22eb-11e9-8689-0017a4770068

Answer 1

按照您的步骤，我确实遇到了同样的问题。但是，如果您使用此 yaml 创建 pod，则它可以正常工作。更改busybox 图像似乎最终会出现您描述的错误。将尝试找出原因。但目前这是解决方案。
apiVersion: v1
kind: Pod
metadata:
name: busybox
namespace: namespace-dev
spec:
containers:
- name: busybox
image: busybox:1.28
command:
- sleep
- "3600"
imagePullPolicy: IfNotPresent
restartPolicy: Always
接着:kubectl exec -ti -n=namespace-dev busybox -- nslookup kubernetes.default它按预期工作并解释here .

/ # nslookup kubernetes
Server:    10.96.0.10
Address 1: 10.96.0.10 kube-dns.kube-system.svc.cluster.local

nslookup: can't resolve 'kubernetes'
/ # nslookup kubernetes.default
Server:    10.96.0.10
Address 1: 10.96.0.10 kube-dns.kube-system.svc.cluster.local

Name:      kubernetes.default
Address 1: 10.96.0.1 kubernetes.default.svc.cluster.local