k8s.github.io

DNS in Kubernetes

In this section, we will take a look at DNS in the Kubernetes Cluster

Pod DNS Record

<POD-IP-ADDRESS>.<namespace-name>.pod.cluster.local

Example ```

Pod is located in a default namespace

10-244-1-10.default.pod.cluster.local

To create a namespace

$ kubectl create ns apps

To create a Pod

$ kubectl run nginx –image=nginx –namespace apps

To get the additional information of the Pod in the namespace “apps”

$ kubectl get po -n apps -owide NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES nginx 1/1 Running 0 99s 10.244.1.3 node01

To get the dns record of the nginx Pod from the default namespace

$ kubectl run -it test –image=busybox:1.28 –rm –restart=Never – nslookup 10-244-1-3.apps.pod.cluster.local Server: 10.96.0.10 Address 1: 10.96.0.10 kube-dns.kube-system.svc.cluster.local

Name: 10-244-1-3.apps.pod.cluster.local Address 1: 10.244.1.3 pod “test” deleted

Accessing with curl command

$ kubectl run -it nginx-test –image=nginx –rm –restart=Never – curl -Is http://10-244-1-3.apps.pod.cluster.local HTTP/1.1 200 OK Server: nginx/1.19.2


## Service DNS Record

- The following DNS resolution:
..svc.cluster.local ``` > Example ``` # Service is located in a default namespace web-service.default.svc.cluster.local ``` - Pod, Service is located in the `apps` namespace ``` # Expose the nginx Pod $ kubectl expose pod nginx --name=nginx-service --port 80 --namespace apps service/nginx-service exposed # Get the nginx-service in the namespace "apps" $ kubectl get svc -n apps NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE nginx-service ClusterIP 10.96.120.174 80/TCP 6s # To get the dns record of the nginx-service from the default namespace $ kubectl run -it test --image=busybox:1.28 --rm --restart=Never -- nslookup nginx-service.apps.svc.cluster.local Server: 10.96.0.10 Address 1: 10.96.0.10 kube-dns.kube-system.svc.cluster.local Name: nginx-service.apps.svc.cluster.local Address 1: 10.96.120.174 nginx-service.apps.svc.cluster.local pod "test" deleted # Accessing with curl command $ kubectl run -it nginx-test --image=nginx --rm --restart=Never -- curl -Is http://nginx-service.apps.svc.cluster.local HTTP/1.1 200 OK Server: nginx/1.19.2 ``` #### References Docs - https://kubernetes.io/docs/concepts/services-networking/dns-pod-service/ - https://kubernetes.io/docs/tasks/administer-cluster/dns-debugging-resolution/