[kubernetes guide ⑤] label quick start

Label

Label yes kubernetes An important concept in the system . Its function is to add identification on resources , Used to distinguish and select them .

Label Characteristics ：

• One Label Will key/value The form of key-value pairs is attached to various objects , Such as Node、Pod、Service wait
• A resource object can be defined in any number of Label , The same Label It can also be added to any number of resource objects
• Label It is usually determined when the resource object is defined , Of course, you can also add or delete objects dynamically after they are created

Can pass Label Realize multi-dimensional grouping of resources , In order to be flexible 、 Easy resource allocation 、 Dispatch 、 To configure 、 Deployment and other management work .

Some commonly used Label Examples are as follows ：

• Version label ：“version”:“release”, “version”:“stable”…
• Environment label ：“environment”:“dev”,“environment”:“test”,“environment”:“pro”
• Architecture Tags ：“tier”:“frontend”,“tier”:“backend”

After the label is defined , Also consider the choice of labels , This is going to use Label Selector, namely ：

Label Used to define the identity of a resource object

Label Selector Used to query and filter resource objects with certain tags

There are currently two Label Selector：

• Based on equality Label Selector

  name = slave: Choose all that contain Label in key="name" And value="slave" The object of

  env != production: Select all, including Label Medium key="env" And value It's not equal to "production" The object of

• Set based Label Selector

  name in (master, slave): Choose all that contain Label Medium key="name" And value="master" or "slave" The object of

  name not in (frontend): Choose all that contain Label Medium key="name" And value It's not equal to "frontend" The object of

The selection criteria of the tag can use multiple , There will be multiple Label Selector Are combined , Use a comma "," Just separate . for example ：

name=slave,env!=production

name not in (frontend),env!=production

Command mode

#  by pod Resource tagging 
[[email protected] ~]# kubectl label pod nginx-pod version=1.0 -n dev
pod/nginx-pod labeled

#  by pod Resource update tag 
[[email protected] ~]# kubectl label pod nginx-pod version=2.0 -n dev --overwrite
pod/nginx-pod labeled

#  View tab 
[[email protected] ~]# kubectl get pod nginx-pod -n dev --show-labels
NAME        READY   STATUS    RESTARTS   AGE   LABELS
nginx-pod   1/1     Running   0          10m   version=2.0

#  Screening tags 
[[email protected] ~]# kubectl get pod -n dev -l version=2.0 --show-labels
NAME        READY   STATUS    RESTARTS   AGE   LABELS
nginx-pod   1/1     Running   0          17m   version=2.0
[[email protected] ~]# kubectl get pod -n dev -l version!=2.0 --show-labels
No resources found in dev namespace.

# Remove the label 
[[email protected] ~]# kubectl label pod nginx-pod version- -n dev
pod/nginx-pod labeled

Configuration mode

apiVersion: v1
kind: Pod
metadata:
  name: nginx
  namespace: dev
  labels:
    version: "3.0" 
    env: "test"
spec:
  containers:
  - image: nginx:latest
    name: pod
    ports:
    - name: nginx-port
      containerPort: 80
      protocol: TCP

Then you can execute the corresponding update command ：kubectl apply -f pod-nginx.yaml

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