88 lines
2.2 KiB
Markdown
88 lines
2.2 KiB
Markdown
# Deploying the DNS Cluster Add-on
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In this lab you will deploy the [DNS add-on](https://kubernetes.io/docs/concepts/services-networking/dns-pod-service/) which provides DNS based service discovery, backed by [CoreDNS](https://coredns.io/), to applications running inside the Kubernetes cluster.
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## The DNS Cluster Add-on
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[//]: # (host:master-1)
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Deploy the `coredns` cluster add-on:
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Note that if you have [changed the service CIDR range](./01-prerequisites.md#service-network) and thus this file, you will need to save your copy onto `master-1` (paste to vi, then save) and apply that.
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```bash
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kubectl apply -f https://raw.githubusercontent.com/mmumshad/kubernetes-the-hard-way/master/deployments/coredns.yaml
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```
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> output
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```
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serviceaccount/coredns created
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clusterrole.rbac.authorization.k8s.io/system:coredns created
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clusterrolebinding.rbac.authorization.k8s.io/system:coredns created
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configmap/coredns created
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deployment.extensions/coredns created
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service/kube-dns created
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```
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List the pods created by the `kube-dns` deployment:
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[//]: # (sleep:15)
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```bash
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kubectl get pods -l k8s-app=kube-dns -n kube-system
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```
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> output
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```
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NAME READY STATUS RESTARTS AGE
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coredns-699f8ddd77-94qv9 1/1 Running 0 20s
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coredns-699f8ddd77-gtcgb 1/1 Running 0 20s
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```
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Reference: https://kubernetes.io/docs/tasks/administer-cluster/coredns/#installing-coredns
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## Verification
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Create a `busybox` pod:
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```bash
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kubectl run busybox --image=busybox:1.28 --command -- sleep 3600
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```
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[//]: # (sleep:10)
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List the pod created by the `busybox` pod:
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```bash
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kubectl get pods -l run=busybox
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```
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> output
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```
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NAME READY STATUS RESTARTS AGE
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busybox-bd8fb7cbd-vflm9 1/1 Running 0 10s
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```
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Execute a DNS lookup for the `kubernetes` service inside the `busybox` pod:
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```bash
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kubectl exec -ti busybox -- nslookup kubernetes
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```
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> output
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```
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Server: 10.96.0.10
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Address 1: 10.96.0.10 kube-dns.kube-system.svc.cluster.local
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Name: kubernetes
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Address 1: 10.96.0.1 kubernetes.default.svc.cluster.local
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```
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Prev: [Kube API Server to Kubelet Connectivity](14-kube-apiserver-to-kubelet.md)</br>
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Next: [Smoke Test](16-smoke-test.md)
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