Labels, selectors, and annotations

Concept and usage

Labels - Properties attached to each item, basically it will match to pod.
Selectors - Filter the items based on labels
Annotations - Record other information for your records like buildVersion, etc.

Normally, we will use labels and selectors to group and select objects.

kubectl get deployments --selector env=prod
kubectl get deployments --selector env=prod,tier=backend

apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-sample-deployment
  labels:
    env: prod
    tier: backend
  annotations: # additional information
    buildVersion: 1.0.0
    author: KarChun
spec:
  selector:
    matchLabels:
      app: sample-app
  template:
    metadata:
      labels:
        app: sample-app
    spec:
      containers:
        - name: my-ubuntu-app
          image: ubuntu

Environments (ConfigMap) and Secrets Services