Kubernetes nslookup kubernetes.default fails

问题

My Environment:

OS - CentOS-8.2
Kubernetes Vesion:
Client Version: v1.18.8
Server Version: v1.18.8

I have successfully configured Kubernetes cluster (One master & one worker), But currently while checking the dns resolution with below code it is failing.

apiVersion: v1
kind: Pod
metadata:
  name: dnsutils
  namespace: default
spec:
  containers:
  - name: dnsutils
    image: gcr.io/kubernetes-e2e-test-images/dnsutils:1.3
    command:
      - sleep
      - "3600"
    imagePullPolicy: IfNotPresent
  restartPolicy: Always


# kubectl get pods -o wide --all-namespaces
NAMESPACE     NAME                                  READY   STATUS    RESTARTS   AGE     IP                NODE           NOMINATED NODE   READINESS GATES
default       dnsutils                              1/1     Running   0          4m38s   10.244.1.20       K8s-Worker-1   <none>            <none>
kube-system   coredns-66bff467f8-2q4z9              1/1     Running   1          4d14h   10.244.0.5        K8s-Master     <none>            <none>
kube-system   coredns-66bff467f8-ktbd4              1/1     Running   1          4d14h   10.244.0.4        K8s-Master     <none>            <none>
kube-system   etcd-K8s-Master                       1/1     Running   1          4d14h   65.66.67.5        K8s-Master     <none>            <none>
kube-system   kube-apiserver-K8s-Master             1/1     Running   1          4d14h   65.66.67.5        K8s-Master     <none>            <none>
kube-system   kube-controller-manager-K8s-Master    1/1     Running   1          4d14h   65.66.67.5        K8s-Master     <none>            <none>
kube-system   kube-flannel-ds-amd64-d6h9c           1/1     Running   61         45h     65.66.67.6        K8s-Worker-1   <none>            <none>
kube-system   kube-flannel-ds-amd64-tc4qf           1/1     Running   202        4d14h   65.66.67.5        K8s-Master     <none>            <none>
kube-system   kube-proxy-cl9n4                      1/1     Running   0          45h     65.66.67.6        K8s-Worker-1   <none>            <none>
kube-system   kube-proxy-s7jlc                      1/1     Running   1          4d14h   65.66.67.5        K8s-Master     <none>            <none>
kube-system   kube-scheduler-K8s-Master             1/1     Running   1          4d14h   65.66.67.5        K8s-Master     <none>            <none>

# kubectl get pods
NAME       READY   STATUS    RESTARTS   AGE
dnsutils   1/1     Running   0          22m

Currently below commands executed on Kubernetes cluster master and nslookup kubernetes.default is failing.

# kubectl exec -i -t dnsutils -- nslookup kubernetes.default
;; connection timed out; no servers could be reached

command terminated with exit code 1


# kubectl exec -ti dnsutils -- cat /etc/resolv.conf
nameserver 10.96.0.10
search default.svc.cluster.local svc.cluster.local cluster.local company.domain.com
options ndots:5


# kubectl get pods --namespace=kube-system -l k8s-app=kube-dns
NAME                       READY   STATUS    RESTARTS   AGE
coredns-66bff467f8-2q4z9   1/1     Running   1          4d14h
coredns-66bff467f8-ktbd4   1/1     Running   1          4d14h

# kubectl logs --namespace=kube-system -l k8s-app=kube-dns
.:53
[INFO] plugin/reload: Running configuration MD5 = 4e235fcc3696966e76816bcd9034ebc7
CoreDNS-1.6.7
linux/amd64, go1.13.6, da7f65b
.:53
[INFO] plugin/reload: Running configuration MD5 = 4e235fcc3696966e76816bcd9034ebc7
CoreDNS-1.6.7
linux/amd64, go1.13.6, da7f65b


# kubectl get svc --namespace=kube-system
NAME       TYPE        CLUSTER-IP   EXTERNAL-IP   PORT(S)                  AGE
kube-dns   ClusterIP   10.96.0.10   <none>        53/UDP,53/TCP,9153/TCP   4d14h

# kubectl get endpoints kube-dns --namespace=kube-system
NAME       ENDPOINTS                                                 AGE
kube-dns   10.244.0.4:53,10.244.0.5:53,10.244.0.4:9153 + 3 more...   4d14h


# kubectl describe svc -n kube-system kube-dns
Name:              kube-dns
Namespace:         kube-system
Labels:            k8s-app=kube-dns
                   kubernetes.io/cluster-service=true
                   kubernetes.io/name=KubeDNS
Annotations:       prometheus.io/port: 9153
                   prometheus.io/scrape: true
Selector:          k8s-app=kube-dns
Type:              ClusterIP
IP:                10.96.0.10
Port:              dns  53/UDP
TargetPort:        53/UDP
Endpoints:         10.244.0.4:53,10.244.0.5:53
Port:              dns-tcp  53/TCP
TargetPort:        53/TCP
Endpoints:         10.244.0.4:53,10.244.0.5:53
Port:              metrics  9153/TCP
TargetPort:        9153/TCP
Endpoints:         10.244.0.4:9153,10.244.0.5:9153
Session Affinity:  None
Events:            <none>

# kubectl describe svc kubernetes
Name:              kubernetes
Namespace:         default
Labels:            component=apiserver
                   provider=kubernetes
Annotations:       <none>
Selector:          <none>
Type:              ClusterIP
IP:                10.96.0.1
Port:              https  443/TCP
TargetPort:        6443/TCP
Endpoints:         65.66.67.5:6443
Session Affinity:  None
Events:            <none>

Can anyone please help me to debug this issue. Thanks.

回答1:

I have uninstalled and re-installed Kubernetes version - v1.19.0 Now everything working fine. Thanks.

来源：https://stackoverflow.com/questions/63653289/kubernetes-nslookup-kubernetes-default-fails

标签

Kubernetes

nslookup

CoreDNS