Centos7 k8s dns

一、搭建dns

　　1、创建skydns-rc.yaml文件

[root@k8s-master opt]# vim 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://192.168.125.130:8080
        # 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

　　2、创建skydns-svc文件

[root@k8s-master opt]# vim 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: 10.254.230.254
  ports:
  - name: dns
    port: 53
    protocol: UDP
  - name: dns-tcp
    port: 53
    protocol: TCP

　　3、创建

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

　　4、查看状态

 　　5、 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 ~]# vim /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=0.0.0.0"

# 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=k8s-node1"

# location of the api-server
KUBELET_API_SERVER="--api-servers=http://192.168.125.130:8080"

# pod infrastructure container
KUBELET_POD_INFRA_CONTAINER="--pod-infra-container-image=192.168.125.130:5000/pod-infrastructure:latest"

# Add your own!
KUBELET_ARGS="--cluster_dns=10.254.230.254 --cluster_domain=cluster.local"                                       添加这一行

　　6、node节点重启服务

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

　　以上就完成了kubernetes的DNS配置，下面测试一下。

二、测试DNS

　　　　1.创建redis-master

[root@k8s-master opt]# 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

　　2、启动redis

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

　　3.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

　　4、启动busybox

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

　　5、通过busybox执行nslookup看能否查找到redis-master

　　6、进入容器测试

[root@k8s-master opt]# kubectl get pods
NAME                                READY     STATUS    RESTARTS   AGE
busybox                             1/1       Running   0          17m
nginx-deployment-3637952344-9cdgs   1/1       Running   2          5d
nginx-deployment-3637952344-ntx44   1/1       Running   2          13h
nginx-deployment-3637952344-shd6t   1/1       Running   2          5d
[root@k8s-master opt]# kubectl exec -it busybox /bin/sh
/ # nslookup kubernnets.default.svc.cluster.local
Server:        10.254.230.254
Address:       10.254.230.254:53