在kubernetes1.2的时候，采用了skydns + kube2dns +etcd的方式来部署dns。而从1.3开始，则部署方式有了一点儿变化，将skydns和kube2dns封装到了一个容器镜像中，放弃了etcd，而将dns解析直接放入到了内存之中，同时引入了dnsmasq，进一步利用其缓存，具体的原理，请查阅相关文档。本篇文档，主要阐述新版的dns在kubernetes中的具体部署。
在Kubernetes的源码目录中，有个cluster/addons/dns目录，下面有几个与dns相关的文件，我们将其中的skydns-rc.yaml.sed以及skydns-svc.yaml.sed文件下载到本地，并去掉后缀。只是拷贝文件的话，可以通过https://rawgit.com这个地址加速，如下：
wget https://rawgit.com/kubernetes/kubernetes/release-1.5/cluster/addons/dns/skydns-rc.yaml.sed -O skydns-rc.yaml
wget https://rawgit.com/kubernetes/kubernetes/release-1.5/cluster/addons/dns/skydns-svc.yaml.sed -O skydns-svc.yaml
下载下来的原文件是用于saltstack自动化安装的，我们手动处理的时候，需要进行相关修改。
修改skydns-rc.yaml内容如下：
# Copyright 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:
#指定副本数
replicas:
# replicas: not specified here:
# . In order to make Addon Manager do not reconcile this replicas parameter.
# . Default is .
# . Will be tuned in real time if DNS horizontal auto-scaling is turned on.
strategy:
rollingUpdate:
maxSurge: %
maxUnavailable:
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
#修改image地址，默认是google的仓库地址，如果不担心被墙，可以直接使用，我这里使用的私有仓库地址，如果要使用国内其他仓库地址，推荐使用阿里云镜像库
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:
scheme: HTTP
initialDelaySeconds:
timeoutSeconds:
successThreshold:
failureThreshold:
readinessProbe:
httpGet:
path: /readiness
port:
scheme: HTTP
# we poll on pod startup for the Kubernetes master service and
# only setup the /readiness HTTP server once that's available.
initialDelaySeconds:
timeoutSeconds:
args:
# --domain指定一级域名，可自定义
- --domain=cluster.local.
- --dns-port=
- --config-map=kube-dns
#增加--kube-master-url，指向kube master的地址
- --kube-master-url=http://10.5.10.116:8080
# This should be set to v= only after the new image (cut from 1.5) has
# been released, otherwise we will flood the logs.
- --v=
#__PILLAR__FEDERATIONS__DOMAIN__MAP__
env:
- name: PROMETHEUS_PORT
value: ""
ports:
- containerPort:
name: dns-local
protocol: UDP
- containerPort:
name: dns-tcp-local
protocol: TCP
- containerPort:
name: metrics
protocol: TCP
- name: dnsmasq
image: myhub.fdccloud.com/library/kube-dnsmasq-amd64:1.4
livenessProbe:
httpGet:
path: /healthz-dnsmasq
port:
scheme: HTTP
initialDelaySeconds:
timeoutSeconds:
successThreshold:
failureThreshold:
args:
- --cache-size=
- --no-resolv
- --server=127.0.0.1#
#- --log-facility=- #注释掉该行
ports:
- containerPort:
name: dns
protocol: UDP
- containerPort:
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:
scheme: HTTP
initialDelaySeconds:
timeoutSeconds:
successThreshold:
failureThreshold:
args:
- --v=
- --logtostderr
ports:
- containerPort:
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 #.
# 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: >/dev/null
- --url=/healthz-kubedns
- --port=
- --quiet
ports:
- containerPort:
protocol: TCP
dnsPolicy: Default # Don't use cluster DNS.
修改skydns-svc.yaml内容如下：
# Copyright 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
#指定clusterIP，后面各pod的dns地址都会指向该地址
clusterIP: 10.254.0.100
ports:
- name: dns
port:
protocol: UDP
- name: dns-tcp
port:
protocol: TCP
启动dns：
kubectl create -f skydns-rc.yaml
kubectl create -f skydns-svc.yaml
修改各node节点上的/etc/kubernetes/kubelet配置文件，增加如下行：
KUBELET_ARGS="--cluster_dns=10.254.0.100 --cluster_domain=cluster.local"
重启各节点：
systemctl restart kubelet
添加一个busybox的pod用于测试，busybox.yaml内容如下：
apiVersion: v1
kind: Pod
metadata:
labels:
name: busybox
role: master
name: busybox
spec:
containers:
- name: busybox
image: myhub.fdccloud.com/library/busybox
command:
- sleep
- ""
执行如下操作：
kubectl exec -it busybox sh
nslookup kubernetes
nslookup kubernetes.default.cluster.local
nslookup kubernetes.default.svc.cluster.local
如果能正常解析，则部署OK。