Installation and deployment testing of DNS in Kubernetes

[TOC]

After DNS is installed, the pod can resolve the service through DNS to enable communication

Kubernetes version:

kubectl version   

My current version is 1.9.0.

1, kubectl DNS installation 1.1 Download the configuration file on the official website

https://github.com/kubernetes/kubernetes具体路径是cluster/addons/dns/kube-dns  可能版本不一样，路径略有不同该路径下有三个相似的配置文件：  kube-dns.yaml.base  kube-dns.yaml.in  kube-dns.yaml.sed  

Here, we use the kube-dns.yaml.sed configuration file as a template;

1.2 You need to modify two of these properties

• $DNS _server_ip Specifies the IP of the k8s DNS, which is apiserver IP by default
• $DNS _domain, replace with cluster.local (consistent with kube-apiserver definition)

1.3 Specific modification commands, you can use the SED command

Copy the kube-dns.yaml.sed configuration file to one of the servers where the k8s cluster resides

• Renaming the configuration file
  • Move kube-dns.yaml.sed Kube-dns.yaml
• Bulk Modify Properties
  • Sed-i ' s/$DNS _server_ip/10.10.10.2/g ' Kube-dns.yaml
  • Sed-i ' s/$DNS _domain/cluster.local/g ' Kube-dns.yaml

1.4 Starting the DNS service

kubectl create -f kube-dns.yaml  

2 Testing DNS Services 2.1 creating a pod and service

Configuration file Curl.yaml

apiVersion: extensions/v1beta1kind: Deploymentmetadata:  name: curl  namespace: kube-systemspec:  replicas: 1  template:    metadata:      labels:        app: curl    spec:      containers:      - name: curl        image: appropriate/curl        command: ["sleep"]        args: ["5000"]---apiVersion: v1kind: Servicemetadata:  name: curl  namespace: kube-system  labels:    app: curlspec:  type: ClusterIP  selector:    app: curl  ports:  - port: 80    targetPort: 80    name: http    protocol: TCP

2.2 Creating a DNS test tool pod

apiVersion: extensions/v1beta1kind: Deploymentmetadata:  name: tools-dns  namespace: defaultspec:  replicas: 1  template:    metadata:      labels:        app: tools-dns    spec:      containers:      - name: tools-dns        image: tutum/dnsutils:latest        command: ["sleep"]        args: ["5000"]

2.3 View just created test pod, Tools-dns

2.4 After entering the container, use the following command to query

kubectl exec -it tools-dns-5665d49688-8jrnw /bin/bash

• View a record (that is, address record IPv4)

  • Nslookup-query=a _http._tcp.curl.kube-system
• View SRV records (a domain Name System (DNS) resource record that identifies the computer that hosts a particular service)
  • Nslookup-query=srv _http._tcp.curl.kube-system
    (Description: Service = 10 (priority) 100 (specific gravity) 80 (port) curl.kube-system.svc.cluster.local (host name).)

2.5 problems found in the test:

1、 如果发现镜像有问题的话，需要更新镜像， 如“k8s.gcr.io/k8s-dns-dnsmasq-nanny-amd64:1.14.10” 改成“ index.tenxcloud.com/jimmy/k8s-dns-dnsmasq-nanny-amd64:1.14.1”将"k8s.gcr.io/k8s-dns-sidecar-amd64:1.14.10" 改成"index.tenxcloud.com/jimmy/k8s-dns-sidecar-amd64:1.14.1"  将" k8s.gcr.io/k8s-dns-kube-dns-amd64:1.14.10" 替换为"index.tenxcloud.com/jimmy/k8s-dns-kube-dns-amd64:1.14.12、如果发现"Liveness probe failed: Get http://172.17.97.2:10054/healthcheck/kubedns: dial tcp 172.17.97.2:10054: getsockopt: connection refused"问题，需要将"SRV"改成"A"

Reference documents:
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Installation and deployment testing of DNS in Kubernetes