Can't resolve 'kubernetes' by skydns serivce in Kubernetes

Question

core@core-1-94 ~ $ kubectl exec -it busybox -- nslookup kubernetes
Server:    10.100.0.10
Address 1: 10.100.0.10

nslookup: can't resolve 'kubernetes'
core@core-1-94 ~ $ kubectl get svc --namespace=kube-system
NAME       LABELS                                                                           SELECTOR           IP(S)            PORT(S)
kube-dns   k8s-app=kube-dns,kubernetes.io/cluster-service=true,kubernetes.io/name=KubeDNS   k8s-app=kube-dns   10.100.0.10      53/UDP
                                                                                                                                53/TCP
kube-ui    k8s-app=kube-ui,kubernetes.io/cluster-service=true,kubernetes.io/name=KubeUI     k8s-app=kube-ui    10.100.110.236   80/TCP
core@core-1-94 ~ $ kubectl exec -it busybox -- nslookup kubernetes 10.100.0.10:53
Server:    10.100.0.10
Address 1: 10.100.0.10

nslookup: can't resolve 'kubernetes'
core@core-1-94 ~ $ kubectl get endpoints --namespace=kube-system
NAME       ENDPOINTS
kube-dns   10.244.31.16:53,10.244.31.16:53
kube-ui    10.244.3.2:8080
core@core-1-94 ~ $ kubectl exec -it busybox -- nslookup kubernetes 10.244.31.16:53
Server:    10.244.31.16
Address 1: 10.244.31.16

Name:      kubernetes
Address 1: 10.100.0.1

I think the service of kube-dns is Not available.

the skydns-svc.yaml :

apiVersion: v1
kind: Service
metadata:
  name: kube-dns
  namespace: kube-system
  labels:
    k8s-app: kube-dns
    kubernetes.io/cluster-service: "true"
    kubernetes.io/name: "KubeDNS"
spec:
  selector:
    k8s-app: kube-dns
  clusterIP: 10.100.0.10
  ports:
  - name: dns
    port: 53
    protocol: UDP
  - name: dns-tcp
    port: 53
    protocol: TCP

Who can help ?

Animesh Kumar Paul Animesh Kumar Paul · Accepted Answer · 2015-09-24T07:03:04

For DNS to work, the kubelet needs to be passed the flags --cluster_dns= and --cluster_domain=cluster.local at startup. This flag isn't included in the set of flags passed to the kubelet, so the kubelet won't try to contact the DNS pod that you've created for name resolution services. To fix this, you can modify the script to add these two flags to the kubelet and then when you create a DNS service, you need to make sure that you set the same ip address that you passed to the --cluster_dns flag as the portalIP field of the service spec like this. For any other information, you can look it.

Can't resolve 'kubernetes' by skydns serivce in Kubernetes

1 Answers