2017-12-08 16:17:16 +08:00
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## 部署 kubedns
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kubedns 是 k8s 集群首先需要部署的，集群中的其他 pods 使用它提供域名解析服务；主要可以解析 `集群服务名` 和 `Pod hostname`；
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配置文件参考 `https://github.com/kubernetes/kubernetes` 项目目录 `kubernetes/cluster/addons/dns`
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2018-01-27 13:54:12 +08:00
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更新 `kube-dns to 1.14.8`，如果集群中已经运行kubedns插件，请使用`RollingUpdate`如下：
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```
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kubectl set image -n kube-system deploy/kube-dns kubedns=mirrorgooglecontainers/k8s-dns-kube-dns-amd64:1.14.8
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kubectl set image -n kube-system deploy/kube-dns dnsmasq=mirrorgooglecontainers/k8s-dns-dnsmasq-nanny-amd64:1.14.8
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kubectl set image -n kube-system deploy/kube-dns sidecar=mirrorgooglecontainers/k8s-dns-sidecar-amd64:1.14.8
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```
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2017-12-08 16:17:16 +08:00
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### 安装
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2017-12-08 17:43:51 +08:00
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**kubectl create -f /etc/ansible/manifests/kubedns/[kubedns.yaml](../../manifests/kubedns/kubedns.yaml)**
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+ 注意deploy中使用的 serviceAccount `kube-dns`，该预定义的 ClusterRoleBinding system:kube-dns 将 kube-system 命名空间的 kube-dns ServiceAccount 与 system:kube-dns ClusterRole 绑定， 因此POD 具有访问 kube-apiserver DNS 相关 API 的权限；
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+ 集群 pod默认继承 node的dns 解析，修改 kubelet服务启动参数 --resolv-conf=""，可以更改这个特性，详见 kubelet 启动参数
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### 验证 kubedns
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新建一个测试nginx服务
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`kubectl run nginx --image=nginx --expose --port=80`
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确认nginx服务
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``` bash
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kubectl get pod|grep nginx
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nginx-7cbc4b4d9c-fl46v 1/1 Running 0 1m
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kubectl get svc|grep nginx
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nginx ClusterIP 10.68.33.167 <none> 80/TCP 1m
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```
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测试pod busybox
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``` bash
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kubectl run busybox --rm -it --image=busybox /bin/sh
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If you don't see a command prompt, try pressing enter.
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/ # cat /etc/resolv.conf
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nameserver 10.68.0.2
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search default.svc.cluster.local. svc.cluster.local. cluster.local.
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options ndots:5
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# 测试集群内部服务解析
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/ # nslookup nginx
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Server: 10.68.0.2
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Address 1: 10.68.0.2 kube-dns.kube-system.svc.cluster.local
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Name: nginx
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Address 1: 10.68.33.167 nginx.default.svc.cluster.local
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/ # nslookup kubernetes
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Server: 10.68.0.2
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Address 1: 10.68.0.2 kube-dns.kube-system.svc.cluster.local
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Name: kubernetes
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Address 1: 10.68.0.1 kubernetes.default.svc.cluster.local
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# 测试外部域名的解析，默认集成node的dns解析
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/ # nslookup www.baidu.com
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Server: 10.68.0.2
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Address 1: 10.68.0.2 kube-dns.kube-system.svc.cluster.local
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Name: www.baidu.com
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Address 1: 180.97.33.108
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Address 2: 180.97.33.107
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/ #
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```
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2017-12-08 16:17:16 +08:00
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2017-12-18 17:35:51 +08:00
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