k8s default service discovery is by dns, will automatically associate the name of service to the clusterIP
HTTP resource allocation list deploy services within the k8s:
On hdss7-200 host, configure a nginx web host to provide a unified configuration within k8s network resource access entry list:
[root@hdss7-200 conf.d]# cat k8s-yaml.od.com.conf server { listen 80; server_name k8s-yaml.od.com; location / { auto index is; default_type text/plain; root /data/k8s-yaml; } } nginx -s reload mkdir -p / data / k8s-yaml / Cored
Configuring DNS network dns in:
named]# vi od.com.zone k8s-yaml A 10.4.7.200 named]# systemctl restart named
Analytical validation:
named]# dig @10.4.7.11 k8s-yaml.od.com +short 10.4.7.200
Installation and deployment CoreDNS, by way of container for delivering software to k8s:
Pulling from the docker-harbor official mirror:
docker pull coredns/coredns:1.6.1 k8s-yaml]# docker tag c0f6e815079e harbor.od.com/public/coredns:v1.6.1 [root@hdss7-200 k8s-yaml]# docker push harbor.od.com/public/coredns:v1.6.1
Preparing a list of resources:
# pwd / Data / k8s-yaml / Cored # cat 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 # cat 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 # cat 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 } # cat 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
Use statement resource management method to apply our resources declarative configuration list:
[root@hdss7-21 ~]# kubectl apply -f http://k8s-yaml.od.com/coredns/rbac.yaml serviceaccount/coredns created clusterrole.rbac.authorization.k8s.io/system:coredns created clusterrolebinding.rbac.authorization.k8s.io/system:coredns created [root@hdss7-21 ~]# kubectl apply -f http://k8s-yaml.od.com/coredns/cm.yaml configmap/coredns created [root@hdss7-21 ~]# kubectl apply -f http://k8s-yaml.od.com/coredns/dp.yaml deployment.apps/coredns created [root@hdss7-21 ~]# kubectl apply -f http://k8s-yaml.od.com/coredns/svc.yaml service/coredns created [root@hdss7-21 ~]# kubectl get all -n kube-system NAME READY STATUS RESTARTS AGE pod/coredns-6b6c4f9648-j7cv9 1/1 Running 0 34s NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE service/coredns ClusterIP 192.168.0.2 <none> 53/UDP,53/TCP,9153/TCP 31s NAME READY UP-TO-DATE AVAILABLE AGE deployment.apps/coredns 1/1 1 1 34s NAME DESIRED CURRENT READY AGE replicaset.apps/coredns-6b6c4f9648 1 1 1 34s
Analytical validation coreDNS is available:
~]# dig -t A www.baidu.com +short @192.168.0.2 www.a.shifen.com. 14.215.177.39 14.215.177.38 ~]# dig -t A harbor.od.com +short @192.168.0.2 10.4.7.200 [root@hdss7-21 ~]# kubectl get svc -n kube-public NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE nginx-dp ClusterIP 192.168.47.82 <none> 80/TCP 10h
We must use the full domain name service outside the cluster to resolve the ip
[root@hdss7-21 ~]# dig -t A nginx-dp.kube-public.svc.cluster.local. @192.168.0.2 +short 192.168.47.82
But if in a cluster, we can use a short domain name, you can see parsing configuration file:
[root@hdss7-21 ~]# kubectl get pod -o wide NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES nginx-ds-rxfqd 1/1 Running 0 11h 172.7.22.2 hdss7-22.host.com <none> <none> nginx-ds-xm5l2 1/1 Running 0 11h 172.7.21.2 hdss7-21.host.com <none> <none> [root@hdss7-21 ~]# kubectl exec -it nginx-ds-xm5l2 -n default bash
The default configuration k8s has helped us to serch, which can use a short domain name to resolve ip address
root@nginx-ds-xm5l2:/# cat /etc/resolv.conf nameserver 192.168.0.2 search default.svc.cluster.local svc.cluster.local cluster.local host.com options ndots:5