Kubernetes Basics-Configuring Kubernetes Skydns Services

Kubernetes Basic Primer-Installation Deployment Configuration Example

Deploying Kubernetes Skydns

Kubernetes can provide DNS internal domain name resolution services for pods.

Kubernetes pause

Its main function is to provide pods with the ability to resolve the IP directly through the service's name to the corresponding service!

Kubernetes pause pod 

1. First add the options in the Kubelet process for each node:

Pause pod kubernetes

kubelet_args= "--cluster_dns=10.254.0.10--cluster_domain=kube.local"

The Master node operates as follows:

[email protected] master/root/yaml]# cat Dns/kubedns-rc.yaml

Kind:replicationcontroller

Metadata

Name:kube-dns-v6

Namespace:default

Labels

K8s-app:kube-dns

Version:v6

Kubernetes.io/cluster-service: "True"

Spec

Replicas:1

Version:v6

Template

Metadata

Labels

K8s-app:kube-dns

Version:v6

Kubernetes.io/cluster-service: "True"

Spec

Containers

-NAME:ETCD

image:index.tenxcloud.com/google_containers/etcd:2.0.9

Command

-/USR/LOCAL/BIN/ETCD

--listen-client-urls

-http://0.0.0.0:2379,http://0.0.0.0:4001

--advertise-client-urls

-http://127.0.0.1:2379,http://127.0.0.1:4001

-Name:kube2sky

image:index.tenxcloud.com/google_containers/kube2sky:1.11

Resources

Limits

cpu:100m

Memory:50mi

Command

-/kube2sky

---kube_master_url=http://192.168.11.10:8080

--domain=kube.local

-Name:skydns

image:index.tenxcloud.com/google_containers/skydns:2015-03-11-001

Resources

Command

-/skydns

--machines=http://localhost:4001

--addr=0.0.0.0:53

--domain=kube.local

Ports

-containerport:53

Name:dns

Protocol:udp

-containerport:53

Name:dns-tcp

Protocol:tcp

Dnspolicy:default

[Email protected] Master yaml]# cat Dns/kubedns-service.yaml

Apiversion:v1

Kind:service

Metadata

Name:kube-dns

Namespace:default

Labels

K8s-app:kube-dns

Kubernetes.io/cluster-service: "True"

Kubernetes.io/name: "Kubedns"

Spec

Selector

K8s-app:kube-dns

clusterip:10.254.0.10

Ports

-Name:dns

port:53

Protocol:udp

-Name:dns-tcp

port:53

Protocol:tcp

Attention: 

(Pause is responsible for managing the pod's network and other related transactions: gcr.io/google_containers/pause-amd64:3.0)

Google is a wall and can be used in the following ways:

1. Turn over the wall or visit the domestic Docker mirror site to download the renamed

[[Email protected] Master yaml]# Docker pull mritd/pause-amd64:3.0

[[Email protected] Master yaml]# Docker tag mritd/pause-amd64:3.0 gcr.io/google_containers/pause-amd64:3.0

2. Using the internal private warehouse, add the following parameters to the Kubelet service process for each k8s node:

"--pod-infra-container-image=my.hub.io/pause-amd64:3.0"

>>> node Mirror list [ Mirror of Private warehouse recommended in real world ]:

# Docker images ( display content is easy to view, so incomplete)

GCR.IO/GOOGLE_CONTAINERS/PAUSE-AMD64 3.0

Index.tenxcloud.com/google_containers/kube2sky 1.11

Index.tenxcloud.com/google_containers/etcd 2.0.9

Index.tenxcloud.com/google_containers/skydns 2015-03-11-001

----------------------------------------------------

[[Email protected] Master yaml]# kubectl create-f dns/kubedns-rc.yaml --validate /Check the correctness of the file and create

[Email protected] Master yaml]# kubectl create-f Dns/kubedns-service.yaml

[[Email protected] Master yaml]# kubectl get RC

NAME Desired Current Age

KUBE-DNS-V6 1 1 38m

[[Email protected] Master yaml]# kubectl Get Svc

NAME cluster-ip external-ip PORT (S) Age

Kube-dns 10.254.0.10 <none> 53/udp,53/tcp 38m

Kubernetes 10.254.0.1 <none> 443/tcp 5h

[[Email protected] Master yaml]# kubectl get svc-o wide //-o wide parameter display details

NAME cluster-ip external-ip PORT (S) Age SELECTOR

Kube-dns 10.254.0.10 <none> 53/udp,53/tcp 2d K8s-app=kube-dns

Kubernetes 10.254.0.1 <none> 443/tcp 3d <none>

2. Test DNS for normal parsing:

First, create a pod named: Mysql-service Service and BusyBox, respectively.

[Email protected] Master yaml]# cat Mysql-server.yaml

Apiversion:v1

Kind:service

Metadata

Labels

Name:mysql

Role:service

Name:mysql-service

Spec

Type:nodeport

Ports

-port:3306

targetport:3306

nodeport:31000

Selector

Name:mysql

[Email protected] Master yaml]# cat Busybox.yaml

Apiversion:v1

Kind:pod

Metadata

Labels

Name:busybox

Role:master

Name:busybox

Spec

Containers

-Name:busybox

Image:busybox

Command

-Sleep

-"360000"

[Email protected] Master yaml]# kubectl create-f Mysql-server.yaml

[Email protected] Master yaml]# kubectl create-f Busybox.yaml

[[Email protected] Master yaml]# kubectl Get Svc

NAME cluster-ip external-ip PORT (S) Age

Kube-dns 10.254.0.10 <none> 53/udp,53/tcp 41m

Kubernetes 10.254.0.1 <none> 443/tcp 5h

Mysql-service 10.254.155.188 <nodes> 3306/tcp 41m

[[Email protected] Master yaml]# kubectl get pod-o Wide

NAME ready STATUS Restarts IP NODE

BusyBox 1/1 Running 0 2d 10.1.77.2 Node1

KUBE-DNS-V6-DFUCV 3/3 Running 0 2d 10.1.62.2 Node2

[[Email protected] Master yaml]# kubectl exec-i-t BusyBox sh

/# nslookup Mysql-service

server:10.254.0.10

Address 1:10.254.0.10

Name:mysql-service

Address 1:10.254.155.188

/# nslookup Mysql-service.default.kube.local

server:10.254.0.10

Address 1:10.254.0.10

Name:mysql-service.default.kube.local

Address 1:10.254.155.188

/# nslookup Mysql-service.default.svc.kube.local

server:10.254.0.10

Address 1:10.254.0.10

Name:mysql-service.default.svc.kube.local

Address 1:10.254.155.188

You can see Mysql-service, mysql-service.default.svc.kube.local, The domain name of the mysql-service.default.kube.local can be correctly parsed into the Mysql-service service of 10.254.155.188.

Mysql-service.default.kube.local is the full domain name, and its composition is <service-name>.<namespace>.<domain-name>

Extended command Operations < more command operations please KUBECTL--HELP or visit the Official KUBECTL command manual >

-# KUBECTL Get RC--namespace=kube-system query specified namespace

-# Kubectl Get pod--all-namespaces=true querying all namespaces

3. Finally, the principle of Kubernetes DNS is briefly introduced.

First, a DNS RC is created at deployment time, resulting in three containers (without pause)

[[email protected] Node2]# Docker ps-a//Run on Kubectl node based on Pod-o get wide node2 above

CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES

033800F393B9 index.alauda.cn/tutum/centos:centos6 "/run.sh" 3 days ago up 3 da Ys 22/tcp Awesome_newton

0FB60DCFB8B4 gcr.io/google_containers/etcd:2.0.9 "/usr/local/bin/etcd" 3 days ago up 3 da Ys K8S_ETCD.8D001F7F_KUBE-DNS-V6-JU8CB_DEFAULT_149FDBA5-4E50-11E6-BA47-0800273D5F3F_6AFE5C27

0A0EFD5F0AAA gcr.io/google_containers/skydns:2015-03-11-001 "/skydns-machines=ht" 3 days ago up 3 da Ys K8s_skydns.5d0f4a29_kube-dns-v6-ju8cb_default_149fdba5-4e50-11e6-ba47-0800273d5f3f_f7c4ee 06

cfef318e4032 gcr.io/google_containers/kube2sky:1.11 "/kube2sky--kube_mas" 3 days ago up 3 da Ys K8s_kube2sky.eb7ac18c_kube-dns-v6-ju8cb_default_149fdba5-4e50-11e6-ba47-0800273d5f3f_19b7 9770

Afad7b2ebd3d docker.io/kubernetes/pause "/pause" 3 days ago up 3 da Ys k8s_pod.87e723e6_kube-dns-v6-ju8cb_default_149fdba5-4e50-11e6-ba47-0800273d5f3f_3c3f7c87

"DNS parsing process"

In the pod that you created, you can view the domain name resolution server that it uses:

[[email protected]]# kubectl exec-i-t BusyBox sh

/# cat/etc/resolv.conf

Search Default.svc.kube.local svc.kube.local kube.local

NameServer 10.254.0.10

Options Ndots:5

When the pod is created in Kubelet, the-cluster_dns=10.254.0.10--cluster_domain=kube.local configured for Kubelet is used, and the corresponding DNS server is used in the pod created.

And this DNS resolution service is actually done by the gcr.io/google_containers/skydns:2015-03-11-001 container 0a0efd5f0aaa in the RC of the DNS.

The Skydns data source is from the gcr.io/google_containers/etcd:2.0.9 container 0fb60dcfb8b4.

[Email protected] Node2]# Docker exec-it 0fb etcdctl get/skydns/local/kube/svc/default/mysql-service/2f1020d6

{"Host": "10.254.162.44", "priority": Ten, "Weight": Ten, "ttl": "0", "Targetstrip"

[email protected] node2]# Docker exec-it 0fb etcdctl Get/skydns/local/kube/default/mysql-service

{"Host": "10.254.162.44", "priority": Ten, "Weight": Ten, "ttl": "0", "Targetstrip"

"Service synchronization Process"

The ETCD data is derived from the cfef318e4032 container created by gcr.io/google_containers/kube2sky:1.11.

The cfef318e4032 container looks at service changes through Watch KUBE-API service.

When the service is created/deleted/modified, the cfef318e4032 container obtains the corresponding service information and stores it in the Etcd container 0fb60dcfb8b4, which is then provided for SKYDNS use.

This article is from the "Jevic" blog, make sure to keep this source http://jevic.blog.51cto.com/2183736/1881898

Kubernetes Basics-Configuring Kubernetes Skydns Services