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쿠버네티스 DNS
- coreDNS : Service 및 Pod용 DNS
kubectl get svc -A
NAMESPACE NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
default kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 57d
default webui-svc ClusterIP 10.96.100.100 <none> 80/TCP 6d19h
ingress-nginx ingress-nginx-controller NodePort 10.100.18.204 <none> 80:30100/TCP,443:30200/TCP 56d
ingress-nginx ingress-nginx-controller-admission ClusterIP 10.99.57.254 <none> 443/TCP 56d
kube-system kube-dns ClusterIP 10.96.0.10 <none> 53/UDP,53/TCP,9153/TCP 77d
- kube-dns Service
1. CLUSTER-IP : 10.96.0.10
2. coreDNS Pod로 동작
kubectl get pod -A | grep dns
kube-system coredns-565d847f94-k9kvr 1/1 Running 25 (14m ago) 77d
kube-system coredns-565d847f94-tdhmn 1/1 Running 25 (14m ago) 77d
core DNS 사용
- kubernetes DNS는 클러스터에서 실행하는 모든 Pod가 사용할 수 있도록 구성된다.
- DNS를 통해 Service와 Pod Access
. service_name.namespace.svc.cluster.local
. Pod-IP-Address.namespace.pod.cluster.local
3개의 pod 및 service 생성
cat deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
name: web
spec:
replicas: 3
selector:
matchLabels:
app: web
template:
metadata:
name: nginx-pod
labels:
app: web
spec:
containers:
- name: nginx-container
image: nginx:1.14
kubectl apply -f deployment.yaml
deployment.apps/web created
cat svc.yaml
apiVersion: v1
kind: Service
metadata:
name: svc-web
spec:
clusterIP: 10.96.100.100
selector:
app: web
ports:
- protocol: TCP
port: 80
targetPort: 80
kubectl apply -f svc.yaml
service/svc-web created
kubectl get all
NAME READY STATUS RESTARTS AGE
pod/web-67b56f4c4c-5r7qm 1/1 Running 0 37s
pod/web-67b56f4c4c-l8bw5 1/1 Running 0 37s
pod/web-67b56f4c4c-thlqw 1/1 Running 0 37s
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
service/kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 57d
service/svc-web ClusterIP 10.96.100.100 <none> 80/TCP 17s
NAME READY UP-TO-DATE AVAILABLE AGE
deployment.apps/web 3/3 3 3 37s
NAME DESIRED CURRENT READY AGE
replicaset.apps/web-67b56f4c4c 3 3 3 37s
NAME COMPLETIONS DURATION AGE
job.batch/centos-job 0/1 58d 58d
curl 명령으로 svc 호출시 pod 3개 중 1개의 pod 로 연결되는것을 확인
curl 10.96.100.100
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
body {
width: 35em;
margin: 0 auto;
font-family: Tahoma, Verdana, Arial, sans-serif;
}
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p>
<p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p>
<p><em>Thank you for using nginx.</em></p>
</body>
</html>
하나의 pod를 생성 후 pod 내 접속
/etc/resolv.conf 확인시 10.96.0.10은 kube-dns 즉, core DNS
kubectl run client-pod --image=centos:7 -it -- /bin/bash
If you don't see a command prompt, try pressing enter.
[root@client-pod /]# cat /etc/resolv.conf
search default.svc.cluster.local svc.cluster.local cluster.local
nameserver 10.96.0.10
options ndots:5
[root@client-pod /]# curl 10.96.100.100
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
body {
width: 35em;
margin: 0 auto;
font-family: Tahoma, Verdana, Arial, sans-serif;
}
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p>
<p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p>
<p><em>Thank you for using nginx.</em></p>
</body>
</html>
search는 dns 호출시 뒤에껄 생략해도 되는걸 의미 default.svc.cluster.local svc.cluster.local cluster.local
curl svc-web.default.svc.cluster.local
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
body {
width: 35em;
margin: 0 auto;
font-family: Tahoma, Verdana, Arial, sans-serif;
}
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p>
<p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p>
<p><em>Thank you for using nginx.</em></p>
</body>
</html>ㅃ
[root@client-pod /]# curl svc-web
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
body {
width: 35em;
margin: 0 auto;
font-family: Tahoma, Verdana, Arial, sans-serif;
}
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p>
<p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p>
<p><em>Thank you for using nginx.</em></p>
</body>
</html>
pod로 직접 호출 가능
[root@client-pod /]# curl 10-36-0-1.default.pod.cluster.local
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
body {
width: 35em;
margin: 0 auto;
font-family: Tahoma, Verdana, Arial, sans-serif;
}
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p>
<p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p>
<p><em>Thank you for using nginx.</em></p>
</body>
</html>
Pod 내 DNS 설정
- 네임서버 및 search 정보가 pod 내 /etc/resolv.conf 파일 내 확인 가능
cat custom-dns.yaml
apiVersion: v1
kind: Pod
metadata:
namespace: default
name: dns-example
spec:
containers:
- name: test
image: nginx
dnsPolicy: "None"
dnsConfig:
nameservers:
- 1.2.3.4
searches:
- ns1.svc.cluster-domain.example
- my.dns.search.suffix
options:
- name: ndots
value: "2"
- name: edns0
kubectl apply -f custom-dns.yaml
pod/dns-example created
kubectl get pods
NAME READY STATUS RESTARTS AGE
client-pod 1/1 Running 0 12m
dns-example 1/1 Running 0 20s
web-67b56f4c4c-5r7qm 1/1 Running 0 26m
web-67b56f4c4c-l8bw5 1/1 Running 0 26m
web-67b56f4c4c-thlqw 1/1 Running 0 26m
kubectl exec dns-example -it -- /bin/bash
root@dns-example:/# cat /etc/resolv.conf
search ns1.svc.cluster-domain.example my.dns.search.suffix
nameserver 1.2.3.4
options ndots:2 edns0
[참고]
- 유투브 따배쿠 강의
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