CoreDNS解决了什么问题？
k8s平台中,各种应用会随机分发到节点服务器上运行,外界无法找到应用的访问地址。

一、配置pod资源定义模板

(本次实验采用网络存储方式来保存pod定义模板,实际应用的时候也可以以本地文件的形式保存)

1.1 配置Nginx （在 k8s-5-141 主机上操作）

  2. #添加nginx转发服务
  3. [root@k8s-5-141 /]# vim /etc/nginx/conf.d/k8s-yaml.od.com.conf
  5. server {
  7.     listen       80;
  9.     server_name  k8s-yaml.od.com;
  11.     location / {
  13.         autoindex on;
  15.         default_type text/plain;
  17.         root /data/k8s-yaml;
  19.     }
  20. }
  22. # 创建需要用到的目录
  23. [root@k8s-5-141 /]# mkdir /data/k8s-yaml/coredns
  25. #重启nginx
  26. [root@k8s-5-141 /]# nginx -t
  27. [root@k8s-5-141 /]# nginx -s reload

1.2 创建 pod 定义模板

  2. # cm.yaml
  4. [root@k8s-5-141 /]# vim /data/k8s-yaml/coredns/cm.yaml 
  6. apiVersion: v1
  7. kind: ConfigMap
  8. metadata:
  9.   name: coredns
  10.   namespace: kube-system
  11. data:
  12.   Corefile: |
  13.     .:53 {
  14.         errors
  15.         log
  16.         health
  17.         ready
  18.         kubernetes cluster.local 192.168.0.0/16    
  19.         forward . 192.168.5.140
  20.         cache 30
  21.         loop
  22.         reload
  23.         loadbalance
  24.        }
  26.  # dp.yaml
  28. [root@k8s-5-141 /]# vim /data/k8s-yaml/coredns/dp.yaml
  29. apiVersion: apps/v1
  30. kind: Deployment
  31. metadata:
  32.   name: coredns
  33.   namespace: kube-system
  34.   labels:
  35.     k8s-app: coredns
  36.     kubernetes.io/name: "CoreDNS"
  37. spec:
  38.   replicas: 1
  39.   selector:
  40.     matchLabels:
  41.       k8s-app: coredns
  42.   template:
  43.     metadata:
  44.       labels:
  45.         k8s-app: coredns
  46.     spec:
  47.       priorityClassName: system-cluster-critical
  48.       serviceAccountName: coredns
  49.       containers:
  50.       - name: coredns
  51.         image: harbor.od.com/public/coredns:1.7.0
  52.         args:
  53.         - -conf
  54.         - /etc/coredns/Corefile
  55.         volumeMounts:
  56.         - name: config-volume
  57.           mountPath: /etc/coredns
  58.         ports:
  59.         - containerPort: 53
  60.           name: dns
  61.           protocol: UDP
  62.         - containerPort: 53
  63.           name: dns-tcp
  64.           protocol: TCP
  65.         - containerPort: 9153
  66.           name: metrics
  67.           protocol: TCP
  68.         livenessProbe:
  69.           httpGet:
  70.             path: /health
  71.             port: 8080
  72.             scheme: HTTP
  73.           initialDelaySeconds: 60
  74.           timeoutSeconds: 5
  75.           successThreshold: 1
  76.           failureThreshold: 5
  77.       dnsPolicy: Default
  78.       volumes:
  79.         - name: config-volume
  80.           configMap:
  81.             name: coredns
  82.             items:
  83.             - key: Corefile
  84.               path: Corefile
  86. #rbac.yaml
  87. [root@k8s-5-141 /]# vim /data/k8s-yaml/coredns/rbac.yaml
  88. apiVersion: v1
  89. kind: ServiceAccount
  90. metadata:
  91.   name: coredns
  92.   namespace: kube-system
  93.   labels:
  94.       kubernetes.io/cluster-service: "true"
  95.       addonmanager.kubernetes.io/mode: Reconcile
  96. ---
  97. apiVersion: rbac.authorization.k8s.io/v1
  98. kind: ClusterRole
  99. metadata:
  100.   labels:
  101.     kubernetes.io/bootstrapping: rbac-defaults
  102.     addonmanager.kubernetes.io/mode: Reconcile
  103.   name: system:coredns
  104. rules:
  105. - apiGroups:
  106.   - ""
  107.   resources:
  108.   - endpoints
  109.   - services
  110.   - pods
  111.   - namespaces
  112.   verbs:
  113.   - list
  114.   - watch
  115. ---
  116. apiVersion: rbac.authorization.k8s.io/v1
  117. kind: ClusterRoleBinding
  118. metadata:
  119.   annotations:
  120.     rbac.authorization.kubernetes.io/autoupdate: "true"
  121.   labels:
  122.     kubernetes.io/bootstrapping: rbac-defaults
  123.     addonmanager.kubernetes.io/mode: EnsureExists
  124.   name: system:coredns
  125. roleRef:
  126.   apiGroup: rbac.authorization.k8s.io
  127.   kind: ClusterRole
  128.   name: system:coredns
  129. subjects:
  130. - kind: ServiceAccount
  131.   name: coredns
  132.   namespace: kube-system
  134.  #svc.yaml
  135. [root@k8s-5-141 /]# vim /data/k8s-yaml/coredns/svc.yaml
  136. apiVersion: v1
  137. kind: Service
  138. metadata:
  139.   name: coredns
  140.   namespace: kube-system
  141.   labels:
  142.     k8s-app: coredns
  143.     kubernetes.io/cluster-service: "true"
  144.     kubernetes.io/name: "CoreDNS"
  145. spec:
  146.   selector:
  147.     k8s-app: coredns
  148.   clusterIP: 192.168.0.2
  149.   ports:
  150.   - name: dns
  151.     port: 53
  152.     protocol: UDP
  153.   - name: dns-tcp
  154.     port: 53
  155.   - name: metrics
  156.     port: 9153
  157.     protocol: TCP

1.3 设置 dns

在 k8s-5-140 服务器上操作

  1. [root@k8s-5-140 ~]# vim /var/named/od.com.zone
  2. $ORIGIN od.com.
  4. $TTL 600  ; 10 minutes
  6. @       IN SOA  dns.od.com. dnsadmin.od.com. (
  8.         2021031605 ; serial
  10.         10800      ; refresh (3 hours)
  12.         900        ; retry (15 minutes)
  14.         604800     ; expire (1 week)
  16.         86400      ; minimum (1 day)
  18.         )
  20.         NS   dns.od.com.
  22. $TTL 60 ; 1 minute
  24. dns          A  192.168.5.140
  25. harbor           A    192.168.5.141
  26. k8s-yaml       A    192.168.5.141 #增加这一行
  28. # 重启named服务
  29. [root@k8s-5-140 ~]# systemctl restart named
  30. [root@k8s-5-140 ~]# dig -t A k8s-yaml.od.com @192.168.5.140 +short
  31. 192.168.5.141

二、下载coredns镜像

在任何一台安装有docker的服务器上操作都行, 我为了验证k8s集群自动部署的效果,所以在运维主机上操作的

  1. [root@k8s-5-141 /]# docker pull coredns/coredns:1.7.0
  2. 1.7.0: Pulling from coredns/coredns
  4. Digest: sha256:73ca82b4ce829766d4f1f10947c3a338888f876fbed0540dc849c89ff256e90c
  5. Status: Image is up to date for coredns/coredns:1.7.0
  6. docker.io/coredns/coredns:1.7.0
  8. [root@k8s-5-141 /]# docker images |grep coredns
  9. coredns/coredns                 1.7.0               bfe3a36ebd25        9 months ago        45.2MB
  11. [root@k8s-5-141 /]# docker tag bfe3a36ebd25 harbor.od.com/public/coredns:1.7.0
  13. [root@k8s-5-141 /]# docker images |grep coredns
  14. coredns/coredns                 1.7.0               bfe3a36ebd25        9 months ago        45.2MB
  15. harbor.od.com/public/coredns    1.7.0               bfe3a36ebd25        9 months ago        45.2MB
  17. [root@alice001 ~]# docker push harbor.od.com/public/coredns:1.7.0
  19. docker push harbor.od.com/public/coredns:1.7.0
  21. The push refers to repository [harbor.od.com/public/coredns]
  23. da1ec456edc8: Pushed
  25. 225df95e717c: Pushed 
  27. 1.7.0: digest: sha256:c7bf0ce4123212c87db74050d4cbab77d8f7e0b49c041e894a35ef15827cf938 size: 739

三、部署 coredns

在任意一台k8s节点服务器上操作

  1. [root@k8s-5-138 ~]# kubectl apply -f http://k8s-yaml.od.com/coredns/rbac.yaml
  3. serviceaccount/coredns created
  5. clusterrole.rbac.authorization.k8s.io/system:coredns created
  7. clusterrolebinding.rbac.authorization.k8s.io/system:coredns created
  9. [root@k8s-5-138 ~]# kubectl apply -f http://k8s-yaml.od.com/coredns/cm.yaml
  11. configmap/coredns created
  13. [root@k8s-5-138 ~]# kubectl apply -f http://k8s-yaml.od.com/coredns/dp.yaml
  15. deployment.apps/coredns created
  17. [root@k8s-5-138 ~]# kubectl apply -f http://k8s-yaml.od.com/coredns/svc.yaml
  19. service/coredns created

四、验证

  1. [root@k8s-5-138 ~]# dig -t A www.baidu.com @192.168.0.2 +short
  2. www.a.shifen.com.
  3. 14.215.177.38
  4. 14.215.177.39
  6. [root@k8s-5-138 ~]# kubectl get svc
  7. NAME         TYPE        CLUSTER-IP        EXTERNAL-IP   PORT(S)   AGE
  8. kubernetes   ClusterIP   192.168.0.1       <none>        443/TCP   7d
  9. nginx-web    ClusterIP   192.168.200.143   <none>        80/TCP    20h
  11. [root@k8s-5-138 ~]# kubectl get svc -n kube-system
  12. NAME      TYPE        CLUSTER-IP    EXTERNAL-IP   PORT(S)                  AGE
  13. coredns   ClusterIP   192.168.0.2   <none>        53/UDP,53/TCP,9153/TCP   20h
  15. [root@k8s-5-138 ~]# dig -t A nginx-web.default.svc.cluster.local @192.168.0.2 +short
  16. 192.168.200.143
  19. #部署应用,检查是否可以通过 
  21. [root@alice002 ~]# kubectl create deployment nginx-ds --image=harbor.od.com/public/nginx:v1.7.9
  23. deployment.apps/nginx-ds created
  25. [root@alice002 ~]# kubectl expose deployment nginx-ds --port=80 --target-port=80 
  27. service/nginx-web exposed