【模块一】kubernetes容器编排进阶实战之CoreDNS的介绍与使用

CoreDNS进阶

CoreDNS进阶-简介

DNS组件历史版本有skydns、kube-dns和coredns三个，k8s 1.3版本之前使用skydns，之后的版本到1.17及之间的版本使用kube-dns，
1.18开始目前主要使用coredns，DNS组件用于解析k8s集群中service name所对应得到IP地址。

https://github.com/coredns/coredns
https://coredns.io
https://coredns.io/plugins/

 CoreDNS进阶-coredns配置文件

[root@k8s-master1 2.dashboard-v2.7.0]#cat ../1.coredns/coredns-v1.9.4.yaml 
# __MACHINE_GENERATED_WARNING__apiVersion: v1
kind: ServiceAccount
metadata:name: corednsnamespace: kube-systemlabels:kubernetes.io/cluster-service: "true"addonmanager.kubernetes.io/mode: Reconcile
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:labels:kubernetes.io/bootstrapping: rbac-defaultsaddonmanager.kubernetes.io/mode: Reconcilename: system:coredns
rules:
- apiGroups:- ""resources:- endpoints- services- pods- namespacesverbs:- list- watch
- apiGroups:- ""resources:- nodesverbs:- get
- apiGroups:- discovery.k8s.ioresources:- endpointslicesverbs:- list- watch
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:annotations:rbac.authorization.kubernetes.io/autoupdate: "true"labels:kubernetes.io/bootstrapping: rbac-defaultsaddonmanager.kubernetes.io/mode: EnsureExistsname: system:coredns
roleRef:apiGroup: rbac.authorization.k8s.iokind: ClusterRolename: system:coredns
subjects:
- kind: ServiceAccountname: corednsnamespace: kube-system
---
apiVersion: v1
kind: ConfigMap
metadata:name: corednsnamespace: kube-systemlabels:addonmanager.kubernetes.io/mode: EnsureExists
data:Corefile: |.:53 {errorshealth {lameduck 5s}readykubernetes cluster.local in-addr.arpa ip6.arpa {pods insecurefallthrough in-addr.arpa ip6.arpattl 30}prometheus :9153#forward . /etc/resolv.conf {forward . 223.6.6.6 {max_concurrent 1000}cache 600loopreloadloadbalance}myserver.online {forward . 172.16.16.16:53}---
apiVersion: apps/v1
kind: Deployment
metadata:name: corednsnamespace: kube-systemlabels:k8s-app: kube-dnskubernetes.io/cluster-service: "true"addonmanager.kubernetes.io/mode: Reconcilekubernetes.io/name: "CoreDNS"
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.replicas: 2strategy:type: RollingUpdaterollingUpdate:maxUnavailable: 1selector:matchLabels:k8s-app: kube-dnstemplate:metadata:labels:k8s-app: kube-dnsspec:securityContext:seccompProfile:type: RuntimeDefaultpriorityClassName: system-cluster-criticalserviceAccountName: corednsaffinity:podAntiAffinity:preferredDuringSchedulingIgnoredDuringExecution:- weight: 100podAffinityTerm:labelSelector:matchExpressions:- key: k8s-appoperator: Invalues: ["kube-dns"]topologyKey: kubernetes.io/hostnametolerations:- key: "CriticalAddonsOnly"operator: "Exists"nodeSelector:kubernetes.io/os: linuxcontainers:- name: corednsimage: coredns/coredns:1.9.4 imagePullPolicy: IfNotPresentresources:limits:memory: 256Mi cpu: 200mrequests:cpu: 100mmemory: 70Miargs: [ "-conf", "/etc/coredns/Corefile" ]volumeMounts:- name: config-volumemountPath: /etc/corednsreadOnly: trueports:- containerPort: 53name: dnsprotocol: UDP- containerPort: 53name: dns-tcpprotocol: TCP- containerPort: 9153name: metricsprotocol: TCPlivenessProbe:httpGet:path: /healthport: 8080scheme: HTTPinitialDelaySeconds: 60timeoutSeconds: 5successThreshold: 1failureThreshold: 5readinessProbe:httpGet:path: /readyport: 8181scheme: HTTPsecurityContext:allowPrivilegeEscalation: falsecapabilities:add:- NET_BIND_SERVICEdrop:- allreadOnlyRootFilesystem: truednsPolicy: Defaultvolumes:- name: config-volumeconfigMap:name: corednsitems:- key: Corefilepath: Corefile
---
apiVersion: v1
kind: Service
metadata:name: kube-dnsnamespace: kube-systemannotations:prometheus.io/port: "9153"prometheus.io/scrape: "true"labels:k8s-app: kube-dnskubernetes.io/cluster-service: "true"addonmanager.kubernetes.io/mode: Reconcilekubernetes.io/name: "CoreDNS"
spec:selector:k8s-app: kube-dnsclusterIP: 10.100.0.2ports:- name: dnsport: 53protocol: UDP- name: dns-tcpport: 53protocol: TCP- name: metricsport: 9153protocol: TCP

 CoreDNS进阶-域名解析

 https://github.com/coredns/deployment/tree/master/kubernetes # vim coredns-v1.X.Y.yaml
 # kubectl apply -f coredns-v1.X.Y.yaml root@k8s-master1:~# kubectl get deployment coredns -n kube-systemNAME READY UP-TO-DATE AVAILABLE AGEcoredns 2/2 2 2 5d20hroot@k8s-master1:~# kubectl run net-test1 --image=centos:7.9.2009 sleep 360000
root@k8s-master1:~# kubectl exec -it net-test1 bash
[root@net-test1 /]# yum install net-tools bind-utils
[root@net-test1 /]# nslookup kubernetes
Server: 10.100.0.2
Address: 10.100.0.2#53
Name: kubernetes.default.svc.cluster.local
Address: 10.100.0.1
[root@net-test1 /]# ping www.jd.com
PING wwwv6.jcloudimg.com (111.31.22.3) 56(84) bytes of data. 64 bytes from 111.31.22.3 (111.31.22.3): icmp_seq=1 ttl=127 time=25.9 ms
64 bytes from 111.31.22.3 (111.31.22.3): icmp_seq=2 ttl=127 time=58.9 ms
[root@net-test1 /]# exit
root@k8s-master1:~# kubectl exec net-test1 nslookup kubernetes.default.svc.cluster.local
Server: 10.100.0.2
Address: 10.100.0.2#53
Name: kubernetes.default.svc.cluster.local
Address: 10.100.0.1
root@k8s-master1:~# kubectl exec net-test1 nslookup kube-dns.kube-system.svc.cluster.local
Server: 10.100.0.2
Address: 10.100.0.2#53
Name: kube-dns.kube-system.svc.cluster.local
Address: 10.100.0.2

CoreDNS进阶-插件配置