Kubernetes Pod With Labels¶

Labels are key/value pairs that are attached to Kubernetes objects, such as pods.

Labels are intended to be used to specify identifying attributes of objects that are meaningful and relevant to users, but do not directly imply semantics to the core system.

Here is the Docker Image used in this tutorial: reyanshkharga/nginx

Step 1: Create Pods With Labels¶

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apiVersion: v1
kind: Pod
metadata:
  name: my-frontend-pod
  labels:
    app: nginx-frontend
    tier: frontend
    environment: dev
spec:
  containers:
  - name: nginx
    image: reyanshkharga/nginx:v1
    imagePullPolicy: Always
    ports:
    - containerPort: 80

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apiVersion: v1
kind: Pod
metadata:
  name: my-backend-pod
  labels:
    app: nginx-backend
    tier: backend
    environment: prod
spec:
  containers:
  - name: nginx
    image: reyanshkharga/nginx:v2
    imagePullPolicy: Always
    ports:
    - containerPort: 80

Apply the manifest files to create pods:

# Create frontend pod
kubectl apply -f frontend.yml

# Create backend pod
kubectl apply -f backend.yml

Step 2: List Pods¶

# List pods
kubectl get pods

# List pods and show labels
kubectl get pods --show-labels

Step 3: Filter Pods Using Labels¶

1. Equality based filtering:

   kubectl get pods -l environment=prod
   kubectl get pods -l environment=dev
   kubectl get pods -l environment=qa
   
   kubectl get pods -l environment=prod,tier=backend
   kubectl get pods -l environment=prod,tier=frontend
   kubectl get pods -l environment=dev,tier=frontend
   kubectl get pods -l environment=qa,tier=backend
   

2. Set based filtering:

   kubectl get pods -l 'environment in (prod, qa)'
   kubectl get pods -l 'environment in (dev, qa)'
   kubectl get pods -l 'environment in (prod, dev)'
   kubectl get pods -l 'environment in (prod, dev, qa)'
   
   kubectl get pods -l 'environment in (prod, qa),tier in (backend, frontend)'
   kubectl get pods -l 'environment in (dev, qa),tier in (backend, frontend)'
   kubectl get pods -l 'environment in (prod, dev),tier in (backend, frontend)'
   kubectl get pods -l 'environment in (prod, dev),tier in (database)'
   

Clean Up¶

# Delete frontend pod
kubectl delete -f frontend.yml

# Delete backend pod
kubectl delete -f backend.yml