一篇特别好的文章：http://ccnuo.com/

服务发现

1.部署kubernetesubernetes的内网资源配置清单

在k8s-60.host.com上，配置一个NGINX，用以提供kubernetes统一的访问资源清单入口

  1. [root@k8s-60 html]# vi /etc/nginx/conf.d/k8s-yaml.od.com.conf
  2. server {
  3.     listen       80;
  4.     server_name  k8s-yaml.od.com;
  6.     location / {
  7.         autoindex on;
  8.         default_type text/plain;
  9.         root /data/k8s-yaml;
  10.     }
  11. }
  12. [root@k8s-60 html]# nginx -t
  13. [root@k8s-60 html]# nginx -s reload
  14. [root@k8s-60 html]# cd /data
  15. [root@k8s-60 data]# mkdir k8s-yaml
  16. [root@k8s-60 data]# cd k8s-yaml/
  17. [root@k8s-60 k8s-yaml]# mkdir coredns

2.配置dns解析

  1. [root@k8s-20 ~]# vi /var/named/od.com.zone
  2. $ORIGIN od.com.
  3. $TTL 600        ; 10 minutes
  4. @               IN SOA  dns.od.com. dnsadmin.od.com. (
  5.                                 2019111003 ; serial
  6.                                 10800      ; refresh (3 hours)
  7.                                 900        ; retry (15 minutes)
  8.                                 604800     ; expire (1 week)
  9.                                 86400      ; minimum (1 day)
  10.                                 )
  11.                                 NS   dns.od.com.
  12. $TTL 60 ; 1 minute
  13. dns                A    192.168.10.20
  14. harbor             A    192.168.10.60
  15. k8s-yaml           A    192.168.10.60
  17. [root@k8s-20 ~]# systemctl restart named
  18. [root@k8s-20 ~]# dig -t A k8s-yaml.od.com @192.168.10.20 +short
  19. 192.168.10.60

3.浏览器访问k8s-yaml.od.com

可以看到有coredns目录

4.下载docker镜像并打包上传到harbor仓库

  1. [root@hdss7-60 ~]# docker pull coredns/coredns:1.6.1
  2. [root@hdss7-60 coredns]# docker tag c0f6e815079e harbor.od.com/public/coredns:v1.6.1
  3. [root@hdss7-60 coredns]# docker push harbor.od.com/public/coredns:v1.6.1

5.准备资源配置清单

官方DNS插件—coredns 模板

  1. https://github.com/kubernetes/kubernetes/tree/master/cluster/addons/dns/coredns

rbac.yaml

权限相关

coredns需要用到集群底层的资源，需要拿到集群权限

  1. [root@k8s-60 coredns]# cd /data/k8s-yaml/coredns/
  2. [root@k8s-60 coredns]# vi rbac.yaml
  3. apiVersion: v1
  4. kind: ServiceAccount
  5. metadata:
  6.   name: coredns
  7.   namespace: kube-system
  8.   labels:
  9.       kubernetes.io/cluster-service: "true"
  10.       addonmanager.kubernetes.io/mode: Reconcile
  11. ---
  12. apiVersion: rbac.authorization.k8s.io/v1
  13. kind: ClusterRole
  14. metadata:
  15.   labels:
  16.     kubernetes.io/bootstrapping: rbac-defaults
  17.     addonmanager.kubernetes.io/mode: Reconcile
  18.   name: system:coredns
  19. rules:
  20. - apiGroups:
  21.   - ""
  22.   resources:
  23.   - endpoints
  24.   - services
  25.   - pods
  26.   - namespaces
  27.   verbs:
  28.   - list
  29.   - watch
  30. ---
  31. apiVersion: rbac.authorization.k8s.io/v1
  32. kind: ClusterRoleBinding
  33. metadata:
  34.   annotations:
  35.     rbac.authorization.kubernetes.io/autoupdate: "true"
  36.   labels:
  37.     kubernetes.io/bootstrapping: rbac-defaults
  38.     addonmanager.kubernetes.io/mode: EnsureExists
  39.   name: system:coredns
  40. roleRef:
  41.   apiGroup: rbac.authorization.k8s.io
  42.   kind: ClusterRole
  43.   name: system:coredns
  44. subjects:
  45. - kind: ServiceAccount
  46.   name: coredns
  47.   namespace: kube-system

cm.yaml

对coredns进行的配置 corefile

  1. [root@k8s-60 coredns]# vi cm.yaml
  2. apiVersion: v1
  3. kind: ConfigMap
  4. metadata:
  5.   name: coredns
  6.   namespace: kube-system
  7. data:
  8.   Corefile: |
  9.     .:53 {
  10.         errors
  11.         log
  12.         health
  13.         ready
  14.         kubernetes cluster.local 10.96.0.0/22
  15.         forward . 192.168.10.20
  16.         cache 30
  17.         loop
  18.         reload
  19.         loadbalance
  20.        }

dp.yaml

coredns 的pod的控制器

  1. [root@k8s-60 coredns]# vi dp.yaml
  2. apiVersion: apps/v1
  3. kind: Deployment
  4. metadata:
  5.   name: coredns
  6.   namespace: kube-system
  7.   labels:
  8.     k8s-app: coredns
  9.     kubernetes.io/name: "CoreDNS"
  10. spec:
  11.   replicas: 1
  12.   selector:
  13.     matchLabels:
  14.       k8s-app: coredns
  15.   template:
  16.     metadata:
  17.       labels:
  18.         k8s-app: coredns
  19.     spec:
  20.       priorityClassName: system-cluster-critical
  21.       serviceAccountName: coredns
  22.       containers:
  23.       - name: coredns
  24.         image: harbor.od.com/public/coredns:v1.6.1
  25.         args:
  26.         - -conf
  27.         - /etc/coredns/Corefile
  28.         volumeMounts:
  29.         - name: config-volume
  30.           mountPath: /etc/coredns
  31.         ports:
  32.         - containerPort: 53
  33.           name: dns
  34.           protocol: UDP
  35.         - containerPort: 53
  36.           name: dns-tcp
  37.           protocol: TCP
  38.         - containerPort: 9153
  39.           name: metrics
  40.           protocol: TCP
  41.         livenessProbe:
  42.           httpGet:
  43.             path: /health
  44.             port: 8080
  45.             scheme: HTTP
  46.           initialDelaySeconds: 60
  47.           timeoutSeconds: 5
  48.           successThreshold: 1
  49.           failureThreshold: 5
  50.       dnsPolicy: Default
  51.       volumes:
  52.         - name: config-volume
  53.           configMap:
  54.             name: coredns
  55.             items:
  56.             - key: Corefile
  57.               path: Corefile

svc.yaml

service

  1. [root@k8s-60 coredns]# vi svc.yaml
  2. apiVersion: v1
  3. kind: Service
  4. metadata:
  5.   name: coredns
  6.   namespace: kube-system
  7.   labels:
  8.     k8s-app: coredns
  9.     kubernetes.io/cluster-service: "true"
  10.     kubernetes.io/name: "CoreDNS"
  11. spec:
  12.   selector:
  13.     k8s-app: coredns
  14.   clusterIP: 10.96.0.2
  15.   ports:
  16.   - name: dns
  17.     port: 53
  18.     protocol: UDP
  19.   - name: dns-tcp
  20.     port: 53
  21.   - name: metrics
  22.     port: 9153
  23.     protocol: TCP

6.应用资源配置

陈述式资源管理方法

  1. [root@k8s-40 ~]# kubectl apply -f http://k8s-yaml.od.com/coredns/rbac.yaml
  2. [root@k8s-40 ~]# kubectl apply -f http://k8s-yaml.od.com/coredns/cm.yaml
  3. [root@k8s-40 ~]# kubectl apply -f http://k8s-yaml.od.com/coredns/dp.yaml
  4. [root@k8s-40 ~]# kubectl apply -f http://k8s-yaml.od.com/coredns/svc.yaml

7.检查创建的资源

  1. [root@k8s-40 ~]# kubectl get all -n kube-system
  2. NAME                           READY   STATUS    RESTARTS   AGE
  3. pod/coredns-6b6c4f9648-8fzsf   1/1     Running   0          17s
  6. NAME              TYPE        CLUSTER-IP   EXTERNAL-IP   PORT(S)                  AGE
  7. service/coredns   ClusterIP   10.96.0.2    <none>        53/UDP,53/TCP,9153/TCP   13s
  8. ## 可以查看到ClusterIP，这个ClusterIP在之前配置的kubelet.sh文件中就已经定好的了
  10. NAME                      READY   UP-TO-DATE   AVAILABLE   AGE
  11. deployment.apps/coredns   1/1     1            1           18s
  13. NAME                                 DESIRED   CURRENT   READY   AGE
  14. replicaset.apps/coredns-6b6c4f9648   1         1         1       17s

10.96.0.2在安装集群的时候已经定好了

/opt/kubernetes/server/bin/kubelet.sh

—cluster-dns 10.96.0.2

CoreNDS是使server_name和cluster_ip关联起来

8.验证coreDNS

  1. [root@k8s-40 ~]# dig -t A www.baidu.com @10.96.0.2 +short
  2. www.a.shifen.com.
  3. 183.232.231.172
  4. 183.232.231.174
  5. [root@k8s-40 ~]# dig -t A k8s-40.host.com @10.96.0.2 +short
  6. 192.168.10.40

coredns原理解析