# 部署 DNS 扩展

本部分将部署 [DNS 扩展](https://kubernetes.io/docs/concepts/services-networking/dns-pod-service/)，用于为集群内的应用提供服务发现。

## DNS 扩展

部属 `kube-dns` 群集扩展:

```bash
kubectl apply -f https://storage.googleapis.com/kubernetes-the-hard-way/coredns-1.7.0.yaml
```

输出为

```bash
serviceaccount/coredns created
clusterrole.rbac.authorization.k8s.io/system:coredns created
clusterrolebinding.rbac.authorization.k8s.io/system:coredns created
configmap/coredns created
deployment.apps/coredns created
service/kube-dns created
```

列出 `kube-dns` 部署的 Pod 列表:

```bash
kubectl get pods -l k8s-app=kube-dns -n kube-system
```

输出为

```bash
NAME                       READY   STATUS    RESTARTS   AGE
coredns-5677dc4cdb-d8rtv   1/1     Running   0          30s
coredns-5677dc4cdb-m8n69   1/1     Running   0          30s
```

## 验证

建立一个 `busybox` 部署:

```bash
kubectl run busybox --image=busybox --command -- sleep 3600
```

列出 `busybox` 部署的 Pod：

```bash
kubectl get pods -l run=busybox
```

输出为

```bash
NAME                       READY     STATUS    RESTARTS   AGE
busybox-2125412808-mt2vb   1/1       Running   0          15s
```

查询 `busybox` Pod 的全名:

```bash
POD_NAME=$(kubectl get pods -l run=busybox -o jsonpath="{.items[0].metadata.name}")
```

在 `busybox` Pod 中查询 DNS：

```bash
kubectl exec -ti $POD_NAME -- nslookup kubernetes
```

输出为

```bash
Server:    10.32.0.10
Address 1: 10.32.0.10 kube-dns.kube-system.svc.cluster.local

Name:      kubernetes
Address 1: 10.32.0.1 kubernetes.default.svc.cluster.local
```

下一步：[烟雾测试](/setup/k8s-hard-way/13-smoke-test.md)。


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://kubernetes.feisky.xyz/setup/k8s-hard-way/12-dns-addon.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.