[Kubernetes] kubernetes label 쿠버네티스 레이블

레이블(Label)이란?

 - Node를 포함하여 pod, deployment 등 모든 리소스에 할당

 - 리소스의 특성을 분류하고, Selector를 이용해서 선택

 - Key-value 한쌍으로 적용

 

Label과 Selector

Label

metadata:
  labels:
    rel: stable
    name: mainui

 

Selector

selector:
  matchLabels:
    key: value
  matchExpressions:
    - {key: name, opertor: In, values: [mainui]}
    - {key: rel, operator: NotIn, values: ["beta","canary"]}

https://kubernetes.io/ko/docs/concepts/overview/working-with-objects/labels/

레이블과 셀렉터

 

Label 명령어 테스트

 

커맨드 명령어를 통해서 pod를 하나 실행하고, label이 없는 pod를 하나와 label이 있는 pod 하나를 실행

※ yaml에서 label은 단순 문자열이 들어갈 경우 ""이 없어도됨. 단, TRUE, FALSE, YES, NO 등의 값은 제외

kubectl run cmdpod --image=nginx:1.14 --port=80
pod/cmdpod created

# cat pod1.yaml 
apiVersion: v1
kind: Pod
metadata:
  name: pod-demo
spec:
  containers:
  - name: nginx
    image: nginx:1.14
    ports:
    - containerPort: 80

# cat pod2.yaml 
apiVersion: v1
kind: Pod
metadata:
  name: label-pod-demo
  labels:
    name: mainui
    rel: stable
spec:
  containers:
  - name: nginx
    image: nginx:1.14
    ports:
    - containerPort: 80
    
# kubectl create -f pod1.yaml -f pod2.yaml 
pod/pod-demo created
pod/label-pod-demo created

# kubectl get pods
NAME             READY   STATUS    RESTARTS   AGE
cmdpod           1/1     Running   0          6m35s
label-pod-demo   1/1     Running   0          9s
pod-demo         1/1     Running   0          9s

 

label 정보 확인

# kubectl get pods --show-labels 
NAME             READY   STATUS    RESTARTS   AGE     LABELS
cmdpod           1/1     Running   0          8m25s   run=cmdpod
label-pod-demo   1/1     Running   0          119s    name=mainui,rel=stable
pod-demo         1/1     Running   0          119s    <none>

 

kubectl get pods -l name=[label명]

 - label명이 같은 pod를 출력(selector)

# kubectl get pods -l name=mainui
NAME             READY   STATUS    RESTARTS   AGE
label-pod-demo   1/1     Running   0          3m4s

# kubectl get pods --selector name=mainui
NAME             READY   STATUS    RESTARTS   AGE
label-pod-demo   1/1     Running   0          3m54s

 

lebel 명령어를 이용하여 추가 가능

# kubectl get pods --show-labels 
NAME             READY   STATUS    RESTARTS   AGE     LABELS
cmdpod           1/1     Running   0          11m     run=cmdpod
label-pod-demo   1/1     Running   0          4m58s   name=mainui,rel=stable
pod-demo         1/1     Running   0          4m58s   <none>

# kubectl label pod pod-demo name=test
pod/pod-demo labeled

# kubectl get pods --show-labels 
NAME             READY   STATUS    RESTARTS   AGE     LABELS
cmdpod           1/1     Running   0          11m     run=cmdpod
label-pod-demo   1/1     Running   0          5m26s   name=mainui,rel=stable
pod-demo         1/1     Running   0          5m26s   name=test

 

--overwrite 속성 : 이미 존재하는 label 위에 덮어쓰기

# kubectl label pod pod-demo name=login
error: 'name' already has a value (test), and --overwrite is false

# kubectl label pod pod-demo name=login --overwrite 
pod/pod-demo labeled

# kubectl get pods --show-labels 
NAME             READY   STATUS    RESTARTS   AGE     LABELS
cmdpod           1/1     Running   0          14m     run=cmdpod
label-pod-demo   1/1     Running   0          7m37s   name=mainui,rel=stable
pod-demo         1/1     Running   0          7m37s   name=login

 

key=value 형식에 맞춰 label 복수 할당

 - 이미 있는 label이라면 --overwrite 필수!

# kubectl get pods --show-labels 
NAME             READY   STATUS    RESTARTS   AGE     LABELS
cmdpod           1/1     Running   0          14m     run=cmdpod
label-pod-demo   1/1     Running   0          7m37s   name=mainui,rel=stable
pod-demo         1/1     Running   0          7m37s   name=login

# kubectl label pod cmdpod name=order rel=beta
pod/cmdpod labeled

# kubectl get pods --show-labels 
NAME             READY   STATUS    RESTARTS   AGE   LABELS
cmdpod           1/1     Running   0          16m   name=order,rel=beta,run=cmdpod
label-pod-demo   1/1     Running   0          10m   name=mainui,rel=stable
pod-demo         1/1     Running   0          10m   name=login

 

label명 뒤에 - (대시문자)

 - label 삭제

# kubectl get pods --show-labels 
NAME             READY   STATUS    RESTARTS   AGE   LABELS
cmdpod           1/1     Running   0          16m   name=order,rel=beta,run=cmdpod
label-pod-demo   1/1     Running   0          10m   name=mainui,rel=stable
pod-demo         1/1     Running   0          10m   name=login

# kubectl label pod cmdpod run-
pod/cmdpod unlabeled

# kubectl get pods --show-labels 
NAME             READY   STATUS    RESTARTS   AGE   LABELS
cmdpod           1/1     Running   0          17m   name=order,rel=beta
label-pod-demo   1/1     Running   0          11m   name=mainui,rel=stable
pod-demo         1/1     Running   0          11m   name=login

 

label로 묶은 내용들은 selector로 확인 가능

# kubectl get pods --show-labels 
NAME             READY   STATUS    RESTARTS   AGE   LABELS
cmdpod           1/1     Running   0          19m   name=order,rel=beta
label-pod-demo   1/1     Running   0          13m   name=mainui,rel=stable
pod-demo         1/1     Running   0          13m   name=login,rel=stable

# kubectl get pods --selector rel=stable
NAME             READY   STATUS    RESTARTS   AGE
label-pod-demo   1/1     Running   0          13m
pod-demo         1/1     Running   0          13m

# kubectl get pods --selector rel=beta
NAME     READY   STATUS    RESTARTS   AGE
cmdpod   1/1     Running   0          20m

# kubectl delete pods --selector rel=beta
pod "cmdpod" deleted

# kubectl get pods --show-labels 
NAME             READY   STATUS    RESTARTS   AGE   LABELS
label-pod-demo   1/1     Running   0          14m   name=mainui,rel=stable
pod-demo         1/1     Running   0          14m   name=login,rel=stable

 

 

[참고]

- https://boansecurity.tistory.com/manage/newpost/?type=post&returnURL=%2Fmanage%2Fposts%2F