Kube-dns是一种易于使用的解决方案，用于在Kubernetes集群中提供DNS服务。本文章将指导您完成在群集中安装kube-dns的过程，以及测试DNS设置以确保其正常工作。完成后，您应该在群集中安装有效的kube-dns，并且pod应该能够成功使用您的DNS。
- 安装kube-dns
- 验证kube-dns pod是否正确启动
- 测试kube-dns
- 故障排错
安装kube-dns
- 准备kube-dns.yaml配置文件
# 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: 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: 10.32.0.10
ports:
- name: dns
port: 53
protocol: UDP
- name: dns-tcp
port: 53
protocol: TCP
---
apiVersion: v1
kind: ServiceAccount
metadata:
name: kube-dns
namespace: kube-system
labels:
kubernetes.io/cluster-service: "true"
addonmanager.kubernetes.io/mode: Reconcile
---
apiVersion: v1
kind: ConfigMap
metadata:
name: kube-dns
namespace: kube-system
labels:
addonmanager.kubernetes.io/mode: EnsureExists
---
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: registry.cn-hangzhou.aliyuncs.com/google_containers/k8s-dns-kube-dns-amd64:1.14.7
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
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: registry.cn-hangzhou.aliyuncs.com/google_containers/k8s-dns-dnsmasq-nanny-amd64:1.14.7
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
- --no-negcache
- --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: registry.cn-hangzhou.aliyuncs.com/google_containers/k8s-dns-sidecar-amd64:1.14.7
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,SRV
- --probe=dnsmasq,127.0.0.1:53,kubernetes.default.svc.cluster.local,5,SRV
ports:
- containerPort: 10054
name: metrics
protocol: TCP
resources:
requests:
memory: 20Mi
cpu: 10m
dnsPolicy: Default # Don't use cluster DNS.
serviceAccountName: kube-dns
注意修改你的这个参数 clusterIP: 10.32.0.10
- 安装kube-dns
kubectl create -f kube-dns.yaml验证kube-dns pod是否正确启动
kubectl get pods -l k8s-app=kube-dns -n kube-system- 你应该得到显示kube-dns pod的输出。它应该看起来像这样：
NAME READY STATUS RESTARTS AGE
kube-dns-598d7bf7d4-spbmj 3/3 Running 0 36s确保3/3容器已准备就绪，并且pod的状态为Running,可能需要一段时间才能完全启动并运行，因此如果READY首先不是3/3，请稍后再检查。
测试kube-dns
- 首先，我们需要启动一个可用于测试的pod：
kubectl run busybox --image=busybox:1.28 --command -- sleep 3600
POD_NAME=$(kubectl get pods -l run=busybox -o jsonpath="{.items[0].metadata.name}")- 接下来，从busybox容器中运行一个nslookup
kubectl exec -ti $POD_NAME -- nslookup kubernetes- 您应该得到如下所示的输出：
Server: 10.32.0.10
Address 1: 10.32.0.10 kube-dns.kube-system.svc.cluster.local
Name: kubernetes
Address 1: 10.32.0.1 kubernetes.default.svc.cluster.local- 如果nslookup成功，那么你的kube-dns安装正在运行！
故障排错
- 我在做最后一步测试的时候，nslookup的时候，报错了，解析失败了
[root@k8s-master example]# kubectl exec -ti busybox -- nslookup kubernetes.default
Server: 10.254.0.2
Address 1: 10.254.0.2
nslookup: can't resolve 'kubernetes.default'
command terminated with exit code 1查看kube-dns的相关信息，找出了错误的所在，实在粗心大意
[root@k8s-master example]# kubectl exec busybox cat /etc/resolv.conf
nameserver 10.254.0.11
search default.svc.cluster.local svc.cluster.local cluster.local nhcdru4itrfetijnzscjvd1jna.ax.internal.chinacloudapp.cn
options ndots:5
[root@k8s-master example]# kubectl get pod -n kube-system
NAME READY STATUS RESTARTS AGE
kube-dns-6db447cbfc-2zmrr 3/3 Running 0 23m
[root@k8s-master example]# kubectl get ep kube-dns --namespace=kube-system
NAME ENDPOINTS AGE
kube-dns 172.17.0.2:53,172.17.0.2:53 25m
[root@k8s-master example]# kubectl get svc --namespace=kube-system
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kube-dns ClusterIP 10.254.0.2 53/UDP,53/TCP 25m - 发现容器里面指定的nameserver为10.254.0.11，但是我的dns服务的ip地址是10.254.0.2，这样不一致肯定解析失败了。最终通过修改kube-dns.yaml，中的clusterIP: 参数，修改为10.254.0.11，并重新构建了kube-dns服务，最终顺利解析。