一：前言
kube-dns是Kubernetes中的一个内置插件，目前作为一个独立的开源项目维护，见https://github.com/kubernetes/dns。通过将 Service 注册到 DNS 中，Kuberentes 可以为我们提供一种简单的服务注册发现与负载均衡方式。至此，别的服务就可以通过名称来访问相关的服务。

Kubernetes DNS pod 中包括 3 个容器：

kubedns：kubedns 进程监视 Kubernetes master 中的 Service 和 Endpoint 的变化，并维护内存查找结构来服务DNS请求。
dnsmasq：dnsmasq 容器添加 DNS 缓存以提高性能。
sidecar：sidecar 容器在执行双重健康检查（针对 dnsmasq 和 kubedns）时提供单个健康检查端点（监听在10054端口）

二：部署kube-dns
1.配置文件
官方网址下载需要的yaml部署文件：https://github.com/kubernetes/kubernetes/tree/release-1.8/cluster/addons/dns
kubedns-cm.yaml
kubedns-sa.yaml
kubedns-controller.yaml
kubedns-svc.yaml

kubedns-cm.yaml不需要修改

点击(此处)折叠或打开

# 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.
apiVersion: v1
kind: ConfigMap
metadata:
name: kube-dns
namespace: kube-system
labels:
addonmanager.kubernetes.io/mode: EnsureExists

kubedns-sa.yaml不需要修改

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apiVersion: v1
kind: ServiceAccount
metadata:
name: kube-dns
namespace: kube-system
labels:
kubernetes.io/cluster-service: "true"
addonmanager.kubernetes.io/mode: Reconcile

kubedns-controller.yaml 主要是$DNS_DOMAIN和image路径的修改

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# 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.
# 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"
addonmanager.kubernetes.io/mode: Reconcile
spec:
# 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: ''
spec:
tolerations:
- key: "CriticalAddonsOnly"
operator: "Exists"
volumes:
- name: kube-dns-config
configMap:
name: kube-dns
optional: true
containers:
- name: kubedns
image: index.tenxcloud.com/jimmy/k8s-dns-kube-dns-amd64:1.14.1
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: /healthcheck/kubedns
port: 10054
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-dir=/kube-dns-config
- --v=2
#__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
volumeMounts:
- name: kube-dns-config
mountPath: /kube-dns-config
- name: dnsmasq
image: index.tenxcloud.com/jimmy/k8s-dns-dnsmasq-nanny-amd64:1.14.1
livenessProbe:
httpGet:
path: /healthcheck/dnsmasq
port: 10054
scheme: HTTP
initialDelaySeconds: 60
timeoutSeconds: 5
successThreshold: 1
failureThreshold: 5
args:
- -v=2
- -logtostderr
- -configDir=/etc/k8s/dns/dnsmasq-nanny
- -restartDnsmasq=true
- --
- -k
- --cache-size=1000
- --log-facility=-
- --server=/cluster.local./127.0.0.1#10053
- --server=/in-addr.arpa/127.0.0.1#10053
- --server=/ip6.arpa/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: 20Mi
volumeMounts:
- name: kube-dns-config
mountPath: /etc/k8s/dns/dnsmasq-nanny
- name: sidecar
image: index.tenxcloud.com/jimmy/k8s-dns-sidecar-amd64:1.14.1
livenessProbe:
httpGet:
path: /metrics
port: 10054
scheme: HTTP
initialDelaySeconds: 60
timeoutSeconds: 5
successThreshold: 1
failureThreshold: 5
args:
- --v=2
- --logtostderr
- --probe=kubedns,127.0.0.1:10053,kubernetes.default.svc.cluster.local.,5,A
- --probe=dnsmasq,127.0.0.1:53,kubernetes.default.svc.cluster.local.,5,A
ports:
- containerPort: 10054
name: metrics
protocol: TCP
resources:
requests:
memory: 20Mi
cpu: 10m
dnsPolicy: Default # Don't use cluster DNS.
serviceAccountName: kube-dns

kubedns-svc.yaml 主要是 clusterIP的修改

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# 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.
# __MACHINE_GENERATED_WARNING__
apiVersion: v1
kind: Service
metadata:
name: kube-dns
namespace: kube-system
labels:
k8s-app: kube-dns
kubernetes.io/cluster-service: "true"
addonmanager.kubernetes.io/mode: Reconcile
kubernetes.io/name: "KubeDNS"
spec:
selector:
k8s-app: kube-dns
clusterIP: 10.254.0.2
ports:
- name: dns
port: 53
protocol: UDP
- name: dns-tcp
port: 53
protocol: TCP

2.系统预定义的 RoleBinding
预定义的 RoleBinding system:kube-dns 将 kube-system 命名空间的kube-dns ServiceAccount 与 system:kube-dns Role 绑定，该 Role 具有访问 kube-apiserver DNS 相关 API 的权限；

3.执行相关文件
kubectl create -f .

三：验证

1.创建一个Deployment
my-nginx.yaml

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apiVersion: extensions/v1beta1
kind: Deployment
metadata:
name: my-nginx
spec:
replicas: 2
template:
metadata:
labels:
run: my-nginx
spec:
containers:
- name: my-nginx
image: docker.io/nginx
ports:
- containerPort: 80

kubectl create -f my-nginx.yaml
2.Export 该 Deployment, 生成 my-nginx 服务
kubectl expose deploy my-nginx

3.往其中一个pod中植入ping 工具
kubectl cp /usr/bin/ping my-nginx-58778897c8-c9x2q:/usr/bin/
kubectl cp /usr/lib64/libidn.so.11 my-nginx-58778897c8-c9x2q:/usr/lib/
kubectl cp /usr/lib64/libcrypto.so.10 my-nginx-58778897c8-c9x2q:/usr/lib/
kubectl cp /usr/lib64/libcap.so.2 my-nginx-58778897c8-c9x2q:/usr/lib/

4.进入pod,执行ping命令进行验证

kubectl exec my-nginx-58778897c8-c9x2q -i -t -- /bin/bash
对应的service名称，自动映射到IP。

或者创建一个简单的busybox pod

busybox.yaml

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apiVersion: v1
kind: Pod
metadata:
name: busybox
namespace: default
spec:
containers:
- image: busybox
command:
- sleep
- "3600"
imagePullPolicy: IfNotPresent
name: busybox
restartPolicy: Always

创建POD
kubectl create -f busybox.yaml
验证
kubectl exec -ti busybox -- nslookup kubernetes.default

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Server: 10.0.0.10
Address 1: 10.0.0.10
Name: kubernetes.default
Address 1: 10.0.0.1

验证成功。

如果出现nslookup: can't resolve 'kubernetes.default' 则说明DNS有问题，通过日志排查错误。

ITPub博客

kubernetes实践之九：kube-dns

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