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# source: k8s_examples/_archived/cluster-dns/README.md type: docs
## Kubernetes DNS example
This is a toy example demonstrating how to use Kubernetes DNS.
### Step Zero: Prerequisites
This example assumes that you have forked the repository and [turned up a Kubernetes cluster](https://kubernetes.io/docs/setup/pick-right-solution/). Make sure DNS is enabled in your setup, see [DNS doc](https://github.com/kubernetes/dns).
```sh
$ cd kubernetes
$ hack/dev-build-and-up.sh
```
### Step One: Create two namespaces
We'll see how cluster DNS works across multiple [namespaces](https://kubernetes.io/docs/concepts/overview/working-with-objects/namespaces/), first we need to create two namespaces:
```sh
$ kubectl create -f examples/staging/cluster-dns/namespace-dev.yaml
$ kubectl create -f examples/staging/cluster-dns/namespace-prod.yaml
```
Now list all namespaces:
```sh
$ kubectl get namespaces
NAME LABELS STATUS
default <none> Active
development name=development Active
production name=production Active
```
For kubectl client to work with each namespace, we define two contexts using our current context as a base:
```sh
$ CURRENT_CONTEXT=$(kubectl config view -o jsonpath='{.current-context}')
$ USER_NAME=$(kubectl config view -o jsonpath='{.contexts[?(@.name == "'"${CURRENT_CONTEXT}"'")].context.user}')
$ CLUSTER_NAME=$(kubectl config view -o jsonpath='{.contexts[?(@.name == "'"${CURRENT_CONTEXT}"'")].context.cluster}')
$ kubectl config set-context dev --namespace=development --cluster=${CLUSTER_NAME} --user=${USER_NAME}
$ kubectl config set-context prod --namespace=production --cluster=${CLUSTER_NAME} --user=${USER_NAME}
```
### Step Two: Create backend replication controller in each namespace
Use the file [`examples/staging/cluster-dns/dns-backend-rc.yaml`](dns-backend-rc.yaml) to create a backend server [replication controller](https://kubernetes.io/docs/concepts/workloads/controllers/replicationcontroller/) in each namespace.
```sh
$ kubectl config use-context dev
$ kubectl create -f examples/staging/cluster-dns/dns-backend-rc.yaml
```
Once that's up you can list the pod in the cluster:
```sh
$ kubectl get rc
CONTROLLER CONTAINER(S) IMAGE(S) SELECTOR REPLICAS
dns-backend dns-backend ddysher/dns-backend name=dns-backend 1
```
Now repeat the above commands to create a replication controller in prod namespace:
```sh
$ kubectl config use-context prod
$ kubectl create -f examples/staging/cluster-dns/dns-backend-rc.yaml
$ kubectl get rc
CONTROLLER CONTAINER(S) IMAGE(S) SELECTOR REPLICAS
dns-backend dns-backend ddysher/dns-backend name=dns-backend 1
```
### Step Three: Create backend service
Use the file [`examples/staging/cluster-dns/dns-backend-service.yaml`](dns-backend-service.yaml) to create
a [service](https://kubernetes.io/docs/concepts/services-networking/service/) for the backend server.
```sh
$ kubectl config use-context dev
$ kubectl create -f examples/staging/cluster-dns/dns-backend-service.yaml
```
Once that's up you can list the service in the cluster:
```sh
$ kubectl get service dns-backend
NAME CLUSTER_IP EXTERNAL_IP PORT(S) SELECTOR AGE
dns-backend 10.0.2.3 <none> 8000/TCP name=dns-backend 1d
```
Again, repeat the same process for prod namespace:
```sh
$ kubectl config use-context prod
$ kubectl create -f examples/staging/cluster-dns/dns-backend-service.yaml
$ kubectl get service dns-backend
NAME CLUSTER_IP EXTERNAL_IP PORT(S) SELECTOR AGE
dns-backend 10.0.2.4 <none> 8000/TCP name=dns-backend 1d
```