Centos7下Kubernetes配置DNS

╰+攻爆jí腚メ 2022-06-02 09:52 207阅读 0赞

# 操作环境 #

网络拓扑图：

![SouthEast][]

OS：

CentOS Linux release 7.4.1708 (Core)

docker：

Client:
     Version:         1.12.6
     API version:     1.24
     Package version: docker-1.12.6-68.gitec8512b.el7.centos.x86_64
     Go version:      go1.8.3
     Git commit:      ec8512b/1.12.6
     Built:           Mon Dec 11 16:08:42 2017
     OS/Arch:         linux/amd64
    
    Server:
     Version:         1.12.6
     API version:     1.24
     Package version: docker-1.12.6-68.gitec8512b.el7.centos.x86_64
     Go version:      go1.8.3
     Git commit:      ec8512b/1.12.6
     Built:           Mon Dec 11 16:08:42 2017
     OS/Arch:         linux/amd64

Kubernetes：

Kubernetes v1.5.2

# 操作步骤 #

## k8s-master配置 ##

编写skydns-rc.yaml文件如下，主要是修改参数kube-master-ur：

[root@k8s-master yaml]# vi skydns-rc.yaml 
    # Copyright 2016 The Kubernetes Authors.
    #
    # Licensed under the Apache License, Version 2.0 (the "License");
    # you may not use this file except in compliance with the License.
    # You may obtain a copy of the License at
    #
    #     http://www.apache.org/licenses/LICENSE-2.0
    #
    # Unless required by applicable law or agreed to in writing, software
    # distributed under the License is distributed on an "AS IS" BASIS,
    # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    # See the License for the specific language governing permissions and
    # limitations under the License.
    
    # TODO - At some point, we need to rename all skydns-*.yaml.* files to kubedns-*.yaml.*
    # Should keep target in cluster/addons/dns-horizontal-autoscaler/dns-horizontal-autoscaler.yaml
    # in sync with this file.
    
    # __MACHINE_GENERATED_WARNING__
    
    apiVersion: extensions/v1beta1
    kind: Deployment
    metadata:
      name: kube-dns
      namespace: kube-system
      labels:
        k8s-app: kube-dns
        kubernetes.io/cluster-service: "true"
    spec:
      replicas: 1
      # replicas: not specified here:
      # 1. In order to make Addon Manager do not reconcile this replicas parameter.
      # 2. Default is 1.
      # 3. Will be tuned in real time if DNS horizontal auto-scaling is turned on.
      strategy:
        rollingUpdate:
          maxSurge: 10%
          maxUnavailable: 0
      selector:
        matchLabels:
          k8s-app: kube-dns
      template:
        metadata:
          labels:
            k8s-app: kube-dns
          annotations:
            scheduler.alpha.kubernetes.io/critical-pod: ''
            scheduler.alpha.kubernetes.io/tolerations: '[{"key":"CriticalAddonsOnly", "operator":"Exists"}]'
        spec:
          containers:
          - name: kubedns
            image: myhub.fdccloud.com/library/kubedns-amd64:1.9
            resources:
              # TODO: Set memory limits when we've profiled the container for large
              # clusters, then set request = limit to keep this container in
              # guaranteed class. Currently, this container falls into the
              # "burstable" category so the kubelet doesn't backoff from restarting it.
              limits:
                memory: 170Mi
              requests:
                cpu: 100m
                memory: 70Mi
            livenessProbe:
              httpGet:
                path: /healthz-kubedns
                port: 8080
                scheme: HTTP
              initialDelaySeconds: 60
              timeoutSeconds: 5
              successThreshold: 1
              failureThreshold: 5
            readinessProbe:
              httpGet:
                path: /readiness
                port: 8081
                scheme: HTTP
              # we poll on pod startup for the Kubernetes master service and
              # only setup the /readiness HTTP server once that's available.
              initialDelaySeconds: 3
              timeoutSeconds: 5
            args:
            - --domain=cluster.local.
            - --dns-port=10053
            - --config-map=kube-dns
            - --kube-master-url=http://10.10.200.224:8080
            # This should be set to v=2 only after the new image (cut from 1.5) has
            # been released, otherwise we will flood the logs.
            - --v=0
            #__PILLAR__FEDERATIONS__DOMAIN__MAP__
            env:
            - name: PROMETHEUS_PORT
              value: "10055"
            ports:
            - containerPort: 10053
              name: dns-local
              protocol: UDP
            - containerPort: 10053
              name: dns-tcp-local
              protocol: TCP
            - containerPort: 10055
              name: metrics
              protocol: TCP
          - name: dnsmasq
            image: myhub.fdccloud.com/library/kube-dnsmasq-amd64:1.4
            livenessProbe:
              httpGet:
                path: /healthz-dnsmasq
                port: 8080
                scheme: HTTP
              initialDelaySeconds: 60
              timeoutSeconds: 5
              successThreshold: 1
              failureThreshold: 5
            args:
            - --cache-size=1000
            - --no-resolv
            - --server=127.0.0.1#10053
            ports:
            - containerPort: 53
              name: dns
              protocol: UDP
            - containerPort: 53
              name: dns-tcp
              protocol: TCP
            # see: https://github.com/kubernetes/kubernetes/issues/29055 for details
            resources:
              requests:
                cpu: 150m
                memory: 10Mi
          - name: dnsmasq-metrics
            image: myhub.fdccloud.com/library/dnsmasq-metrics-amd64:1.0
            livenessProbe:
              httpGet:
                path: /metrics
                port: 10054
                scheme: HTTP
              initialDelaySeconds: 60
              timeoutSeconds: 5
              successThreshold: 1
              failureThreshold: 5
            args:
            - --v=2
            - --logtostderr
            ports:
            - containerPort: 10054
              name: metrics
              protocol: TCP
            resources:
              requests:
                memory: 10Mi
          - name: healthz
            image: myhub.fdccloud.com/library/exechealthz-amd64:1.2
            resources:
              limits:
                memory: 50Mi
              requests:
                cpu: 10m
                # Note that this container shouldn't really need 50Mi of memory. The
                # limits are set higher than expected pending investigation on #29688.
                # The extra memory was stolen from the kubedns container to keep the
                # net memory requested by the pod constant.
                memory: 50Mi
            args:
            - --cmd=nslookup kubernetes.default.svc.cluster.local 127.0.0.1 >/dev/null
            - --url=/healthz-dnsmasq
            - --cmd=nslookup kubernetes.default.svc.cluster.local 127.0.0.1:10053 >/dev/null
            - --url=/healthz-kubedns
            - --port=8080
            - --quiet
            ports:
            - containerPort: 8080
              protocol: TCP
          dnsPolicy: Default

编写skydns-svc.yaml，主要是修改参数clusterIP，因为kubernetes cluster中flannel设置的ip为172.17.0.0网段，所以设置

clusterIP为172.17.0.3

[root@k8s-master yaml]# vi skydns-svc.yaml 
    # Copyright 2016 The Kubernetes Authors.
    #
    # Licensed under the Apache License, Version 2.0 (the "License");
    # you may not use this file except in compliance with the License.
    # You may obtain a copy of the License at
    #
    #     http://www.apache.org/licenses/LICENSE-2.0
    #
    # Unless required by applicable law or agreed to in writing, software
    # distributed under the License is distributed on an "AS IS" BASIS,
    # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    # See the License for the specific language governing permissions and
    # limitations under the License.
    
    # TODO - At some point, we need to rename all skydns-*.yaml.* files to kubedns-*.yaml.*
    
    # __MACHINE_GENERATED_WARNING__
    
    apiVersion: v1
    kind: Service
    metadata:
      name: kube-dns
      namespace: kube-system
      labels:
        k8s-app: kube-dns
        kubernetes.io/cluster-service: "true"
        kubernetes.io/name: "KubeDNS"
    spec:
      selector:
        k8s-app: kube-dns
      clusterIP: 172.17.0.3
      ports:
      - name: dns
        port: 53
        protocol: UDP
      - name: dns-tcp
        port: 53
        protocol: TCP

启用上述2文件

[root@k8s-master yaml]# kubectl create -f skydns-rc.yaml
    [root@k8s-master yaml]# kubectl create -f skydns-svc.yaml

查看状态

[root@k8s-master yaml]# kubectl get services --all-namespaces
    NAMESPACE     NAME                   CLUSTER-IP       EXTERNAL-IP   PORT(S)         AGE
    default       glusterfs-cluster      172.17.62.135    <none>        1/TCP           1d
    default       redis-master           172.17.136.235   <none>        6379/TCP        1h
    default       wordpress              172.17.110.149   <pending>     80:30503/TCP    1h
    default       wordpress-mysql        None             <none>        3306/TCP        1h
    kube-system   kube-dns               172.17.0.3       <none>        53/UDP,53/TCP   1h
    kube-system   kubernetes-dashboard   172.17.161.157   <none>        80/TCP          4d
    kube-system   tiller-deploy          172.17.134.91    <none>        44134/TCP       1d
    
    [root@k8s-master yaml]# kubectl get deployment  --all-namespaces
    NAMESPACE     NAME                   DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGE
    default       wordpress              1         1         1            1           1h
    default       wordpress-mysql        1         1         1            1           1h
    kube-system   kube-dns               1         1         1            1           1h
    kube-system   kubernetes-dashboard   1         1         1            1           4d
    kube-system   tiller-deploy          1         1         1            0           1d

## k8s-node配置 ##

在k8s-node节点主要配置/etc/kubernetes/kubelet文件，添加参数配置KUBELET\_ARGS如下：

[root@k8s-node1 ~]# vi /etc/kubernetes/kubelet 
    ###
    # kubernetes kubelet (minion) config
    
    # The address for the info server to serve on (set to 0.0.0.0 or "" for all interfaces)
    KUBELET_ADDRESS="--address=10.10.200.229"
    
    # The port for the info server to serve on
    # KUBELET_PORT="--port=10250"
    
    # You may leave this blank to use the actual hostname
    KUBELET_HOSTNAME="--hostname-override=10.10.200.229"
    
    # location of the api-server
    KUBELET_API_SERVER="--api-servers=http://10.10.200.224:8080"
    
    # pod infrastructure container
    KUBELET_POD_INFRA_CONTAINER="--pod-infra-container-image=registry.access.redhat.com/rhel7/pod-infrastructure:latest"
    
    # Add your own!
    KUBELET_ARGS="--cluster_dns=172.17.0.3 --cluster_domain=cluster.local"

重启kubelet

[root@k8s-node1 ~]# systemctl restart kubelet.service

以上就完成了kubernetes的DNS配置，下面测试一下。

## 测试DNS ##

1.创建redis-master

[root@k8s-master yaml]# vi redis.yaml 
    apiVersion: v1
    kind: Service
    metadata:
      name: redis-master
      labels:
        name: redis-master
    spec:
      selector:
        name: redis-master
      ports:
      - port: 6379
        targetPort: 6379

启动redis

[root@k8s-master yaml]# kubectl create -f redis.yaml 
    service "redis-master" created

2.创建带有nslookup的busybox

[root@k8s-master yaml]# vi busybox.yaml 
    apiVersion: v1
    kind: Pod
    metadata:
        name: busybox
        namespace: default
    spec:
        containers:
          - image: docker.io/busybox
            command:
              - sleep
              - "3600"
            imagePullPolicy: IfNotPresent
            name: busybox
        restartPolicy: Always

启动busybox

[root@k8s-master yaml]# kubectl create -f busybox.yaml 
    pod "busybox" created

通过busybox执行nslookup看能否查找到redis-master

[root@k8s-master yaml]# kubectl exec busybox -- nslookup redis-master
    Server:    172.17.0.3
    Address 1: 172.17.0.3 kube-dns.kube-system.svc.cluster.local
    
    Name:      redis-master
    Address 1: 172.17.188.179 redis-master.default.svc.cluster.local

##     ##

[SouthEast]: /images/20220602/964c247c760b49efb931443f2eac7a2b.png