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This article will explain in detail the example analysis of installing kubernetes 1.6 kube-dns under ubuntu 16.04. the editor thinks it is very practical, so I share it with you for reference. I hope you can get something after reading this article.

1 preface

If service solves the problem of pod service discovery and load balancing, then kube-dns is born to solve the problem of service discovery. Imagine such a scenario. If an application wants to access the backend service without knowing the service ip, it can only query the IP and port corresponding to the service with kubectl get svc-n namespace, and then change the configuration, so that the configuration of each new service will be changed, which is troublesome enough. Then if this problem is solved, this is the content of this article.

2 use kube-dns to discover service

The kube-dns plug-in provides three container functions as follows:

Kubedns container

Monitor kubernetes service resources and update DNS records

Replace etcd, use TreeCache data structure to save DNS records and implement the backend interface of skydns

Connect to skydns and provide DNS query service to dnsmasq

Dnsmasq container

Provide DNS query service to the cluster

Set kubedns to upstream

Provide DNS cache to reduce kubedns load and improve performance

Exechealthz container

Regularly check the monitoring status of kubedns and dnsmasq

To provide HTTP API for kubernetes activity detection.

3 kubedns,dnsmasq,exechealthz schematic

4 kube-dns plug-in installation

The installation of kube-dns actually starts three containers: kubedns,dnsmasq,exechealthz

Create a kube-dns service first

Cat kubedns-svc.yaml

ApiVersion: v1

Kind: Service

Metadata:

Name: kube-dns

Namespace: kube-system

Labels:

K8s-app: kube-dns

Spec:

Selector:

K8s-app: kube-dns

ClusterIP: 10.10.10.10 # is consistent with the-cluster-dns of the kubelet startup parameters of each node * *

Ports:

-name: dns

Port: 53

Protocol: UDP

-name: dns-tcp

Port: 53

Protocol: TCP

Create kube-dns RC, create three containers

Cat kubedns-rc.yaml

ApiVersion: v1

Kind: ReplicationController

Metadata:

Name: kube-dns-v6

Namespace: kube-system

Labels:

K8s-app: kube-dns

Version: v6

Kubernetes.io/cluster-service: "true"

Spec:

Replicas: 1

Selector:

K8s-app: kube-dns

Version: v6

Template:

Metadata:

Labels:

K8s-app: kube-dns

Version: v6

Spec:

Containers:

-name: kubedns

Image: siriuszg/kubedns-amd64:latest

ImagePullPolicy: IfNotPresent

Resources:

Limits:

Cpu: 100m

Memory: 50Mi

LivenessProbe:

HttpGet:

Path: / healthz-kubedns

Port: 8080

Scheme: HTTP

InitialDelaySeconds: 60

TimeoutSeconds: 5

SuccessThreshold: 1

FailureThreshold: 5

ReadinessProbe:

HttpGet:

Path: / readiness

Port: 8081

Scheme: HTTP

InitialDelaySeconds: 3

TimeoutSeconds: 5

Args:

-domain=cluster.local. # is consistent with the startup parameter-cluster-domain in the kubelet of each node. There is a "." * * after cluster.local.

-dns-port=10053

-kube-master-url= http://192.168.100.20:8080

Ports:

-containerPort: 10053

Name: dns-local

Protocol: UDP

-name: kube-dnsmasq

Image: ist0ne/kube-dnsmasq-amd64:latest

ImagePullPolicy: IfNotPresent

LivenessProbe:

HttpGet:

Path: / healthz-dnsmasq

Port: 8080

Scheme: HTTP

InitialDelaySeconds: 60

TimeoutSeconds: 5

SuccessThreshold: 1

FailureThreshold: 5

Args:

-cache-size=1000

-no-resolv

-server=127.0.0.1#10053

-log-facility=-

Ports:

-containerPort: 53

Name: dns

Protocol: UDP

-containerPort: 53

Name: dns-tcp

Protocol: TCP

-name: healthz

Image: ist0ne/exechealthz-amd64:latest

ImagePullPolicy: IfNotPresent

Resources:

Limits:

Memory: 50Mi

Requests:

Cpu: 10m

Memory: 50Mi

Args:

-cmd=nslookup kubernetes.default.svc.cluster.local 127.0.0.1 > / dev/null

-url=/healthz-dnsmasq

-cmd=nslookup kubernetes.default.svc.cluster.local 127.0.0.1 10053 > / dev/null

-url=/healthz-kubedns

-port=8080

-quiet

Ports:

-containerPort: 8080

Protocol: TCP

DnsPolicy: Default

Note: the values of-- cluster-dns and-- cluster-domain,--cluster-dns should be added to the kubelet startup parameters of each node. The values of-- cluster-dns and-- cluster-domain,--cluster-dns are the values of clusterIP in service: 10.10.10.10.

In this way, the container startup automatically adds the following fields to / etc/resolv.conf

Execute kubectl create-f kubedns-svc.yaml and kubectl create-f kubedns-rc.yaml to create service and pod of kubedns, respectively

5 Verification

Through the above steps, the plug-in for kube-dns is installed. First, let's take a look at what we have installed. We can view the service,rc and pod we created through kubectl or dashboard. The screenshot below is viewed through kubectl.

You can see from the figure that the pod of kube-dns-v6-41d2c is started. On the node 192.168.100.93, the assigned IP is 172.17.2.5. A total of three containers are enabled, and the three containers share IP.

Find a pod from default namespace and use this pod to verify kube-dns

Choose the pod tomcat-gllz3 because the container in this pod contains nslookup.

It can be seen from the figure that all service can be parsed through kubedns.

Note: the domain name rule of kubedns is service-name.namespace.svc.domain

Service-name is the name of a service

Namespace is the namespace in which the service is located

Svc is a fixed character

Domain is the domain specified when creating the kubedns pod, that is, the cluster-domain in the kubelete startup parameters of each node. This article is cluster.local.

On the "ubuntu 16.04 installation of kubernetes 1.6 kube-dns sample analysis" this article is shared here, I hope the above content can be of some help to you, so that you can learn more knowledge, if you think the article is good, please share it out for more people to see.

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