核心链接
https://kubernetes.io/docs/ta...
CoreDNS 安装
apiVersion: v1 kind: ServiceAccount metadata: name: coredns namespace: kube-system --- apiVersion: rbac.authorization.k8s.io/v1beta1 kind: ClusterRole metadata: labels: kubernetes.io/bootstrapping: rbac-defaults name: system:coredns rules: - apiGroups: - "" resources: - endpoints - services - pods - namespaces verbs: - list - watch --- apiVersion: rbac.authorization.k8s.io/v1beta1 kind: ClusterRoleBinding metadata: annotations: rbac.authorization.kubernetes.io/autoupdate: "true" labels: kubernetes.io/bootstrapping: rbac-defaults name: system:coredns roleRef: apiGroup: rbac.authorization.k8s.io kind: ClusterRole name: system:coredns subjects: - kind: ServiceAccount name: coredns namespace: kube-system --- apiVersion: v1 kind: ConfigMap metadata: name: coredns namespace: kube-system data: Corefile: | .:53 { log errors health kubernetes cluster.local 172.0.0.0/8 in-addr.arpa ip6.arpa { pods insecure upstream fallthrough in-addr.arpa ip6.arpa } prometheus :9153 proxy . /etc/resolv.conf cache 30 reload } --- apiVersion: extensions/v1beta1 kind: Deployment metadata: name: coredns namespace: kube-system labels: k8s-app: coredns kubernetes.io/name: "CoreDNS" spec: replicas: 2 strategy: type: RollingUpdate rollingUpdate: maxUnavailable: 1 selector: matchLabels: k8s-app: coredns template: metadata: labels: k8s-app: coredns spec: serviceAccountName: coredns tolerations: - key: "CriticalAddonsOnly" operator: "Exists" containers: - name: coredns image: hub.issll.com/kubernetes/coredns:1.1.0 imagePullPolicy: IfNotPresent 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 livenessProbe: httpGet: path: /health port: 8081 scheme: HTTP initialDelaySeconds: 60 timeoutSeconds: 5 successThreshold: 1 failureThreshold: 5 dnsPolicy: Default volumes: - name: config-volume configMap: name: coredns items: - key: Corefile path: Corefile --- apiVersion: v1 kind: Service metadata: name: kube-dns namespace: kube-system labels: k8s-app: coredns kubernetes.io/cluster-service: "true" kubernetes.io/name: "CoreDNS" spec: selector: k8s-app: coredns clusterIP: 172.21.0.2 ports: - name: dns port: 53 protocol: UDP - name: dns-tcp port: 53 protocol: TCP
在master结点上执行
kubectl apply -f coredns.yaml
主要修改文件
nodes结点上的/etc/resolv.conf
$ cat /etc/resolv.conf # Generated by NetworkManager search default.svc.cluster.local middleware.svc.cluster.local svc.cluster.local cluster.local nameserver 192.168.1.254
打印每个pods上的出错日志
for p in $(kubectl get pods --namespace=kube-system -l k8s-app=coredns -o name); do kubectl logs --namespace=kube-system $p; done
用busybox 检验coredns解析效果
kubectl exec -ti busybox -- nslookup redis-master
因为结点上的search 域的设定,等于
kubectl exec -ti busybox -- nslookup redis-master.middleware.svc.cluster.local
这里 redis-master 是布署在 middleware 命名空间下的一个pod
CoreDNS 已知 Bug
重新加载时,在启动新服务器实例之前停止运行状况处理程序。如果新服务器无法启动,则初始服务器实例仍然可用且仍然提供DNS查询,但Health处理程序保持关闭状态。在成功重新加载或完全重新启动CoreDNS之前,Health运行状况不会回复HTTP请求。
后记
在新 pod 创建后, CoreDNS 更新有问题, 需要解决