kubernetes集群配置dns服务

本文将在前文的基础上介绍在kubernetes集群环境中配置dns服务，在k8s集群中，pod的生命周期是短暂的，pod重启后ip地址会产生变化，对于应用程序来说这是不可接受的，为解决这个问题，K8S集群巧妙的引入的dns服务来实现服务的发现，在k8s集群中dns总共需要使用4个组件，各组件分工如下：
etcd：DNS存储
kube2sky：将Kubernetes Master中的service（服务）注册到etcd。
skyDNS：提供DNS域名解析服务。
healthz：提供对skydns服务的健康检查。

一、下载相关镜像文件，并纳入本地仓库统一管理

# docker pull docker.io/elcolio/etcd # docker pull docker.io/port/kubernetes-kube2sky# docker pull docker.io/skynetservices/skydns # docker pull docker.io/wu1boy/healthz# docker tag docker.io/elcolio/etcd registry.fjhb.cn/etcd# docker tag docker.io/port/kubernetes-kube2sky registry.fjhb.cn/kubernetes-kube2sky# docker tag docker.io/skynetservices/skydns ?registry.fjhb.cn/skydns# docker tag docker.io/wu1boy/healthz registry.fjhb.cn/healthz# docker push registry.fjhb.cn/etcd# docker push registry.fjhb.cn/kubernetes-kube2sky# docker push registry.fjhb.cn/skydns# docker push registry.fjhb.cn/healthz# docker images |grep fjhb

二、通过rc文件创建pod
这里面一个pod包含了4个组件，一个组件运行在一个docker容器中

# cat skydns-rc.yamlapiVersion: v1kind: ReplicationControllermetadata: ?name: kube-dns ?namespace: default ?labels: ???k8s-app: kube-dns ???version: v12 ???kubernetes.io/cluster-service: "true"spec: ?replicas: 1 ?selector: ???k8s-app: kube-dns ???version: v12 ?template: ???metadata: ?????labels: ???????k8s-app: kube-dns ???????version: v12 ???????kubernetes.io/cluster-service: "true" ???spec: ?????containers: ?????- name: etcd ???????image: registry.fjhb.cn/etcd ????????resources: ?????????limits: ???????????cpu: 100m ???????????memory: 50Mi ?????????requests: ???????????cpu: 100m ???????????memory: 50Mi ???????command: ???????- /bin/etcd ???????- --data-dir ???????- /tmp/data ???????- --listen-client-urls ???????- http://127.0.0.1:2379,http://127.0.0.1:4001 ???????- --advertise-client-urls ???????- http://127.0.0.1:2379,http://127.0.0.1:4001 ???????- --initial-cluster-token ???????- skydns-etcd ???????volumeMounts: ???????- name: etcd-storage ?????????mountPath: /tmp/data ?????- name: kube2sky ???????image: registry.fjhb.cn/kubernetes-kube2sky ???????resources: ?????????limits: ???????????cpu: 100m ???????????memory: 50Mi ?????????requests: ???????????cpu: 100m ???????????memory: 50Mi ???????args: ???????- -kube_master_url=http://192.168.115.5:8080 ???????- -domain=cluster.local ?????- name: skydns ???????image: registry.fjhb.cn/skydns ????????resources: ?????????limits: ???????????cpu: 100m ???????????memory: 50Mi ?????????requests: ???????????cpu: 100m ???????????memory: 50Mi ???????args: ???????- -machines=http://127.0.0.1:4001 ???????- -addr=0.0.0.0:53 ???????- -ns-rotate=false ???????- -domain=cluster.local ???????ports: ???????- containerPort: 53 ?????????name: dns ?????????protocol: UDP ???????- containerPort: 53 ?????????name: dns-tcp ?????????protocol: TCP ?????- name: healthz ???????image: registry.fjhb.cn/healthz ???????resources: ?????????limits: ???????????cpu: 10m ???????????memory: 20Mi ?????????requests: ???????????cpu: 10m ???????????memory: 20Mi ???????args: ???????- -cmd=nslookup kubernetes.default.svc.cluster.local 127.0.0.1 >/dev/null ???????- -port=8080 ???????ports: ???????- containerPort: 8080 ?????????protocol: TCP ?????volumes: ?????- name: etcd-storage ???????emptyDir: {} ?????dnsPolicy: Default

三、通过srv文件创建service

# cat skydns-svc.yaml ??apiVersion: v1kind: Servicemetadata: ?name: kube-dns ?namespace: default ?labels: ???k8s-app: kube-dns ???kubernetes.io/cluster-service: "true" ???kubernetes.io/name: "KubeDNS"spec: ?selector: ???k8s-app: kube-dns ?clusterIP: 10.254.16.254 ?ports: ?- name: dns ???port: 53 ???protocol: UDP ?- name: dns-tcp ???port: 53 ???protocol: TCP

# kubectl create -f skydns-rc.yaml # kubectl create -f skydns-svc.yaml # kubectl get rc# kubectl get pod# kubectl get svc

# kubectl describe svc kube-dns

# kubectl describe rc kube-dns

# kubectl describe pod kube-dns-9fllpName: ??????????kube-dns-9fllpNamespace: ?????defaultNode: ??????????192.168.115.6/192.168.115.6Start Time: ????Tue, 23 Jan 2018 10:55:19 -0500Labels: ????????k8s-app=kube-dns ???????????????kubernetes.io/cluster-service=true ???????????????version=v12Status: ????????RunningIP: ????????????172.16.37.5Controllers: ???ReplicationController/kube-dnsContainers: ?etcd: ???Container ID: ??????docker://62ad76bfaca1797c5f43b0e9eebc04074169fce4cc15ef3ffc4cd19ffa9c8c19 ???Image: ?????????????registry.fjhb.cn/etcd ???Image ID: ??????????docker-pullable://docker.io/elcolio/etcd@sha256:3b4dcd35a7eefea9ce2970c81dcdf0d0801a778d117735ee1d883222de8bbd9f ???Port: ???Command: ?????/bin/etcd ?????--data-dir ?????/tmp/data ?????--listen-client-urls ?????http://127.0.0.1:2379,http://127.0.0.1:4001 ?????--advertise-client-urls ?????http://127.0.0.1:2379,http://127.0.0.1:4001 ?????--initial-cluster-token ?????skydns-etcd ???Limits: ?????cpu: ?????100m ?????memory: ??50Mi ???Requests: ?????cpu: ?????????????100m ?????memory: ??????????50Mi ???State: ?????????????Running ?????Started: ?????????Tue, 23 Jan 2018 10:55:23 -0500 ???Ready: ?????????????True ???Restart Count: ?????0 ???Volume Mounts: ?????/tmp/data from etcd-storage (rw) ?????/var/run/secrets/kubernetes.io/serviceaccount from default-token-6pddn (ro) ???Environment Variables: ?????<none> ?kube2sky: ???Container ID: ??????docker://6b0bc6e8dce83e3eee5c7e654fbaca693730623fb7936a1fd9d73de1a1dd8152 ???Image: ?????????????registry.fjhb.cn/kubernetes-kube2sky ???Image ID: ??????????docker-pullable://docker.io/port/kubernetes-kube2sky@sha256:0230d3fbb0aeb4ddcf903811441cf2911769dbe317a55187f58ca84c95107ff5 ???Port: ???Args: ?????-kube_master_url=http://192.168.115.5:8080 ?????-domain=cluster.local ???Limits: ?????cpu: ?????100m ?????memory: ??50Mi ???Requests: ?????cpu: ?????????????100m ?????memory: ??????????50Mi ???State: ?????????????Running ?????Started: ?????????Tue, 23 Jan 2018 10:55:25 -0500 ???Ready: ?????????????True ???Restart Count: ?????0 ???Volume Mounts: ?????/var/run/secrets/kubernetes.io/serviceaccount from default-token-6pddn (ro) ???Environment Variables: ?????<none> ?skydns: ???Container ID: ??????docker://ebc2aaaa54e2f922e370e454ec537665d813c69d37a21e3afd908e6dad056627 ???Image: ?????????????registry.fjhb.cn/skydns ???Image ID: ??????????docker-pullable://docker.io/skynetservices/skydns@sha256:6f8a9cff0b946574bb59804016d3aacebc637581bace452db6a7515fa2df79ee ???Ports: ?????????????53/UDP, 53/TCP ???Args: ?????-machines=http://127.0.0.1:4001 ?????-addr=0.0.0.0:53 ?????-ns-rotate=false ?????-domain=cluster.local ???Limits: ?????cpu: ?????100m ?????memory: ??50Mi ???Requests: ?????cpu: ?????????????100m ?????memory: ??????????50Mi ???State: ?????????????Running ?????Started: ?????????Tue, 23 Jan 2018 10:55:27 -0500 ???Ready: ?????????????True ???Restart Count: ?????0 ???Volume Mounts: ?????/var/run/secrets/kubernetes.io/serviceaccount from default-token-6pddn (ro) ???Environment Variables: ?????<none> ?healthz: ???Container ID: ??????docker://f1de1189fa6b51281d414d7a739b86494b04c8271dc6bb5f20c51fac15ec9601 ???Image: ?????????????registry.fjhb.cn/healthz ???Image ID: ??????????docker-pullable://docker.io/wu1boy/healthz@sha256:d6690c0a8cc4f810a5e691b6a9b8b035192cb967cb10e91c74824bb4c8eea796 ???Port: ??????????????8080/TCP ???Args: ?????-cmd=nslookup kubernetes.default.svc.cluster.local 127.0.0.1 >/dev/null ?????-port=8080 ???Limits: ?????cpu: ?????10m ?????memory: ??20Mi ???Requests: ?????cpu: ?????????????10m ?????memory: ??????????20Mi ???State: ?????????????Running ?????Started: ?????????Tue, 23 Jan 2018 10:55:29 -0500 ???Ready: ?????????????True ???Restart Count: ?????0 ???Volume Mounts: ?????/var/run/secrets/kubernetes.io/serviceaccount from default-token-6pddn (ro) ???Environment Variables: ?????<none>Conditions: ?Type ?????????Status ?Initialized ??True ??Ready ????????True ??PodScheduled ?True Volumes: ?etcd-storage: ???Type: ??????EmptyDir (a temporary directory that shares a pod‘s lifetime) ???Medium: ?default-token-6pddn: ???Type: ??????Secret (a volume populated by a Secret) ???SecretName: default-token-6pddnQoS Class: ?????GuaranteedTolerations: ???<none>Events: ?FirstSeen ????LastSeen ???????Count ??From ???????????????????SubObjectPath ??????????????????Type ???????????Reason ???????Message ?--------- ????-------- ???????----- ??---- ???????????????????------------- ??????????????????-------- ???????------ ???????------- ?7m ???????????7m ?????????????1 ??????{default-scheduler } ???????????????????????????????????Normal ?????????Scheduled ????Successfully assigned kube-dns-9fllp to 192.168.115.6 ?7m ???????????7m ?????????????1 ??????{kubelet 192.168.115.6} spec.containers{etcd} ??????????Normal ?????????Pulling ??????pulling image "registry.fjhb.cn/etcd" ?7m ???????????7m ?????????????1 ??????{kubelet 192.168.115.6} spec.containers{etcd} ??????????Normal ?????????Pulled ???????Successfully pulled image "registry.fjhb.cn/etcd" ?7m ???????????7m ?????????????1 ??????{kubelet 192.168.115.6} spec.containers{etcd} ??????????Normal ?????????Created ??????Created container with docker id 62ad76bfaca1; Security:[seccomp=unconfined] ?7m ???????????7m ?????????????1 ??????{kubelet 192.168.115.6} spec.containers{kube2sky} ??????Normal ?????????Pulled ???????Successfully pulled image "registry.fjhb.cn/kubernetes-kube2sky" ?7m ???????????7m ?????????????1 ??????{kubelet 192.168.115.6} spec.containers{etcd} ??????????Normal ?????????Started ??????Started container with docker id 62ad76bfaca1 ?7m ???????????7m ?????????????1 ??????{kubelet 192.168.115.6} spec.containers{kube2sky} ??????Normal ?????????Pulling ??????pulling image "registry.fjhb.cn/kubernetes-kube2sky" ?7m ???????????7m ?????????????1 ??????{kubelet 192.168.115.6} spec.containers{kube2sky} ??????Normal ?????????Created ??????Created container with docker id 6b0bc6e8dce8; Security:[seccomp=unconfined] ?7m ???????????7m ?????????????1 ??????{kubelet 192.168.115.6} spec.containers{skydns} ????????Normal ?????????Pulled ???????Successfully pulled image "registry.fjhb.cn/skydns" ?7m ???????????7m ?????????????1 ??????{kubelet 192.168.115.6} spec.containers{skydns} ????????Normal ?????????Pulling ??????pulling image "registry.fjhb.cn/skydns" ?7m ???????????7m ?????????????1 ??????{kubelet 192.168.115.6} spec.containers{kube2sky} ??????Normal ?????????Started ??????Started container with docker id 6b0bc6e8dce8 ?7m ???????????7m ?????????????1 ??????{kubelet 192.168.115.6} spec.containers{skydns} ????????Normal ?????????Created ??????Created container with docker id ebc2aaaa54e2; Security:[seccomp=unconfined] ?7m ???????????7m ?????????????1 ??????{kubelet 192.168.115.6} spec.containers{skydns} ????????Normal ?????????Started ??????Started container with docker id ebc2aaaa54e2 ?7m ???????????7m ?????????????1 ??????{kubelet 192.168.115.6} spec.containers{healthz} ???????Normal ?????????Pulling ??????pulling image "registry.fjhb.cn/healthz" ?7m ???????????7m ?????????????1 ??????{kubelet 192.168.115.6} spec.containers{healthz} ???????Normal ?????????Pulled ???????Successfully pulled image "registry.fjhb.cn/healthz" ?7m ???????????7m ?????????????1 ??????{kubelet 192.168.115.6} spec.containers{healthz} ???????Normal ?????????Created ??????Created container with docker id f1de1189fa6b; Security:[seccomp=unconfined] ?7m ???????????7m ?????????????1 ??????{kubelet 192.168.115.6} spec.containers{healthz} ???????Normal ?????????Started ??????Started container with docker id f1de1189fa6b

四、修改kubelet配置文件并重启服务
注意:
--cluster-dns参数要和前面svc文件中的clusterIP参数一致
--cluster-domain参数要和前面rc文件中的-domain参数一致
集群内所有的kubelet节点都需要修改

# grep ‘KUBELET_ADDRESS‘ /etc/kubernetes/kubelet ????KUBELET_ADDRESS="--address=192.168.115.5 --cluster-dns=10.254.16.254 --cluster-domain=cluster.local"# systemctl restart kubelet

五、运行一个busybox和curl进行测试

# cat busybox.yaml apiVersion: v1kind: Podmetadata: ?name: busyboxspec: ?containers: ?- name: busybox ???image: docker.io/busybox ???command: ???- sleep- "3600"

# cat curl.yaml apiVersion: v1kind: Podmetadata: ?name: curlspec: ?containers: ?- name: curl ???image: docker.io/webwurst/curl-utils ???command: ???- sleep- "3600"

# kubectl create -f busybox.yaml # kubectl create -f curl.yaml

通过busybox容器对kubernetes的service进行解析，发现service被自动解析成了对应的集群ip地址，而并不是172.16网段的docker地址

# kubectl get svc# kubectl exec busybox -- nslookup frontend# kubectl exec busybox -- nslookup redis-master# kubectl exec busybox -- nslookup redis-slave

通过curl容器访问前面创建的php留言板

# kubectl exec curl -- curl frontend

kubernetes集群配置dns服务

原文地址：http://blog.51cto.com/ylw6006/2067923