1.kubernetes的服务发现插件-CoreDNS

1.1 部署kubernetesubernetes的内网资源配置清单

在运维主机上(hdss7-200.host.com上)准备Coredns镜像文件，以docker镜像文件的方式部署到Kubernetes集群中去。

[root@hdss7-200 ~]# vi /etc/nginx/conf.d/k8s-yaml.od.com.conf
server {
    listen       80;
    server_name  k8s-yaml.od.com;

    location / {
        autoindex on;
        default_type text/plain;
        root /data/k8s-yaml;
    }
}
[root@hdss7-200 ~]# nginx -t
[root@hdss7-200 ~]# nginx -s reload
[root@hdss7-200 ~]# cd /data
[root@hdss7-200 data]# mkdir k8s-yaml
[root@hdss7-200 data]# cd k8s-yaml/
[root@hdss7-200 k8s-yaml]# mkdir coredns

1.2 配置dns解析（注意是在hdss7-11上）

[root@hdss7-11 ~]# vi /var/named/od.com.zone
$ORIGIN od.com.
$TTL 600        ; 10 minutes
@               IN SOA  dns.od.com. dnsadmin.od.com. (
                                2019111003 ; serial
                                10800      ; refresh (3 hours)
                                900        ; retry (15 minutes)
                                604800     ; expire (1 week)
                                86400      ; minimum (1 day)
                                )
                                NS   dns.od.com.
$TTL 60 ; 1 minute
dns                A    10.4.7.11
harbor             A    10.4.7.200
k8s-yaml           A    10.4.7.200

[root@hdss7-11 ~]# systemctl restart named
[root@hdss7-11 ~]# dig -t A k8s-yaml.od.com @10.4.7.11 +short
10.4.7.200

1.3 下载docker镜像并打包上传到harbor仓库（在hdss7-200上）

[root@hdss7-200 ~]# docker pull coredns/coredns:1.6.1
[root@hdss7-200 coredns]# pwd
/data/k8s-yaml/coredns
[root@hdss7-200 coredns]# docker tag c0f6e815079e harbor.od.com/public/coredns:v1.6.1
[root@hdss7-200 coredns]# docker  push harbor.od.com/public/coredns:v1.6.1

1.4 准备资源配置清单

rbac.yaml

[root@hdss7-200 coredns]# vim rbac.yaml
apiVersion: v1
kind: ServiceAccount
metadata:
  name: coredns
  namespace: kube-system
  labels:
      kubernetes.io/cluster-service: "true"
      addonmanager.kubernetes.io/mode: Reconcile
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  labels:
    kubernetes.io/bootstrapping: rbac-defaults
    addonmanager.kubernetes.io/mode: Reconcile
  name: system:coredns
rules:
- apiGroups:
  - ""
  resources:
  - endpoints
  - services
  - pods
  - namespaces
  verbs:
  - list
  - watch
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  annotations:
    rbac.authorization.kubernetes.io/autoupdate: "true"
  labels:
    kubernetes.io/bootstrapping: rbac-defaults
    addonmanager.kubernetes.io/mode: EnsureExists
  name: system:coredns
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: system:coredns
subjects:
- kind: ServiceAccount
  name: coredns
  namespace: kube-system

cm.yaml（注意forward）

[root@hdss7-200 coredns]# vi cm.yaml
apiVersion: v1
kind: ConfigMap
metadata:
  name: coredns
  namespace: kube-system
data:
  Corefile: |
    .:53 {
        errors
        log
        health
        ready
        kubernetes cluster.local 192.168.0.0/16
        forward . 10.4.7.11
        cache 30
        loop
        reload
        loadbalance
       }

dp.yaml

[root@hdss7-200 coredns]# vi dp.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: coredns
  namespace: kube-system
  labels:
    k8s-app: coredns
    kubernetes.io/name: "CoreDNS"
spec:
  replicas: 1
  selector:
    matchLabels:
      k8s-app: coredns
  template:
    metadata:
      labels:
        k8s-app: coredns
    spec:
      priorityClassName: system-cluster-critical
      serviceAccountName: coredns
      containers:
      - name: coredns
        image: harbor.od.com/public/coredns:v1.6.1
        args:
        - -conf
        - /etc/coredns/Corefile
        volumeMounts:
        - name: config-volume
          mountPath: /etc/coredns
        ports:
        - containerPort: 53
          name: dns
          protocol: UDP
        - containerPort: 53
          name: dns-tcp
          protocol: TCP
        - containerPort: 9153
          name: metrics
          protocol: TCP
        livenessProbe:
          httpGet:
            path: /health
            port: 8080
            scheme: HTTP
          initialDelaySeconds: 60
          timeoutSeconds: 5
          successThreshold: 1
          failureThreshold: 5
      dnsPolicy: Default
      volumes:
        - name: config-volume
          configMap:
            name: coredns
            items:
            - key: Corefile
              path: Corefile

svc.yaml

[root@hdss7-200 coredns]# vi svc.yaml
apiVersion: v1
kind: Service
metadata:
  name: coredns
  namespace: kube-system
  labels:
    k8s-app: coredns
    kubernetes.io/cluster-service: "true"
    kubernetes.io/name: "CoreDNS"
spec:
  selector:
    k8s-app: coredns
  clusterIP: 192.168.0.2
  ports:
  - name: dns
    port: 53
    protocol: UDP
  - name: dns-tcp
    port: 53
  - name: metrics
    port: 9153
    protocol: TCP

1.5 应用资源配置

在master主机（21、22）任意一台执行

[root@hdss7-21 ~]# kubectl apply -f http://k8s-yaml.od.com/coredns/rbac.yaml
[root@hdss7-21 ~]# kubectl apply -f http://k8s-yaml.od.com/coredns/cm.yaml
[root@hdss7-21 ~]# kubectl apply -f http://k8s-yaml.od.com/coredns/dp.yaml
[root@hdss7-21 ~]# kubectl apply -f http://k8s-yaml.od.com/coredns/svc.yaml

1.6 检查创建的资源

[root@hdss7-21 ~]# kubectl get all -n kube-system -o wide
NAME                           READY   STATUS    RESTARTS   AGE   IP           NODE                NOMINATED NODE   READINESS GATES
pod/coredns-6b6c4f9648-9r89z   1/1     Running   0          42m   172.7.21.3   hdss7-21.host.com   <none>           <none>


NAME              TYPE        CLUSTER-IP    EXTERNAL-IP   PORT(S)                  AGE   SELECTOR
service/coredns   ClusterIP   192.168.0.2   <none>        53/UDP,53/TCP,9153/TCP   42m   k8s-app=coredns


NAME                      READY   UP-TO-DATE   AVAILABLE   AGE   CONTAINERS   IMAGES                                SELECTOR
deployment.apps/coredns   1/1     1            1           42m   coredns      harbor.od.com/public/coredns:v1.6.1   k8s-app=coredns

NAME                                 DESIRED   CURRENT   READY   AGE   CONTAINERS   IMAGES                                SELECTOR
replicaset.apps/coredns-6b6c4f9648   1         1         1       42m   coredns      harbor.od.com/public/coredns:v1.6.1   k8s-app=coredns,pod-template-hash=6b6c4f9648