[CKA] Kube-DNS

[문제]

* Create a nginx pod called nginx-resolver using image nginx, expose it internally with a service called nginx-resolver-service.
* Test that you are able to look up the service and pod names from within the cluster. Use the image busybox:1.28 for dns lookup
 - Record result in /tmp/nginx.svc and /tmp/nginx.pod
 - pod: nginx-resolver created
 - Service DNS Resolution recorded correctly
 - Pod DNS resolution recorede correctly

 

[풀이]

pod 및 expose 생성

# kubectl run nginx-resolver --image=nginx
pod/nginx-resolver created

# kubectl expose pod nginx-resolver --name nginx-resolver-service --port=80 --target-port=80
service/nginx-resolver-service exposed

# kubectl get pod nginx-resolver -o wide
NAME             READY   STATUS    RESTARTS   AGE   IP          NODE                NOMINATED NODE   READINESS GATES
nginx-resolver   1/1     Running   0          47s   10.36.0.1   node1.example.com   <none>           <none>

# kubectl get svc nginx-resolver-service
NAME                     TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)   AGE
nginx-resolver-service   ClusterIP   10.110.175.16   <none>        80/TCP    47s

 

pod 및 service에 대한 nslookup

- docs 문서에서 dns 내용 확인

https://kubernetes.io/docs/concepts/services-networking/dns-pod-service/

DNS for Services and Pods

 

dns 질의를 위한 busybox 이미지 파드를 임시로 생성

# kubectl run test --image=busybox:1.28 --rm -it --restart=Never -- /bin/sh
If you don't see a command prompt, try pressing enter.
/ # cat /etc/resolv.conf
search default.svc.cluster.local svc.cluster.local cluster.local
nameserver 10.96.0.10
options ndots:5

 

service nslookup 조회

/ # nslookup nginx-resolver-service.default.svc.cluster.local
Server:    10.96.0.10
Address 1: 10.96.0.10 kube-dns.kube-system.svc.cluster.local

Name:      nginx-resolver-service.default.svc.cluster.local
Address 1: 10.110.175.16 nginx-resolver-service.default.svc.cluster.local

 

pod nslookup 조회

/ # nslookup 10-36-0-1.default.pod.cluster.local
Server:    10.96.0.10
Address 1: 10.96.0.10 kube-dns.kube-system.svc.cluster.local

Name:      10-36-0-1.default.pod.cluster.local
Address 1: 10.36.0.1 10-36-0-1.nginx-resolver-service.default.svc.cluster.local

/ # exit
pod "test" deleted

 

service, pod nslookup 조회 결과 저장

# cat > /tmp/nginx.svc
Server:    10.96.0.10
Address 1: 10.96.0.10 kube-dns.kube-system.svc.cluster.local

Name:      nginx-resolver-service.default.svc.cluster.local
Address 1: 10.110.175.16 nginx-resolver-service.default.svc.cluster.local

# cat > /tmp/nginx.pod
Server:    10.96.0.10
Address 1: 10.96.0.10 kube-dns.kube-system.svc.cluster.local

Name:      10-36-0-1.default.pod.cluster.local
Address 1: 10.36.0.1 10-36-0-1.nginx-resolver-service.default.svc.cluster.local

 

 

[참고]

- 유투브 따배씨