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Kubernetes Services with Pod Creation

CKAD

1. Introduction to Kubernetes Services

  • Purpose: Kubernetes Services allow for the exposure of applications running on Pods, both within the cluster and externally.
  • Types of Services: Includes ClusterIP for internal exposure and NodePort for external exposure.

2. Creating a Sample Application Pod

  • Objective: Deploy a simple web application pod to demonstrate service exposure.

  • Pod YAML Example:

    apiVersion: v1
kind: Pod
metadata:
  name: web-app-pod
  labels:
    app: web-app
spec:
  containers:
  - name: nginx-container
    image: nginx

  • Explanation: This creates a pod named web-app-pod with an Nginx container, labeled app: web-app, which we will expose using Services.

3. Exposing the Pod with a ClusterIP Service

  • Objective: Expose the web-app-pod within the cluster.

  • Service YAML Example:

    apiVersion: v1
kind: Service
metadata:
  name: clusterip-web-service
spec:
  type: ClusterIP
  selector:
    app: web-app
  ports:
    - protocol: TCP
      port: 8081
      targetPort: 80

  • Explanation: The clusterip-web-service exposes the web-app-pod inside the cluster on TCP port 8081.

4. Exposing the Pod with a NodePort Service

  • Objective: Expose the web-app-pod externally, outside the Kubernetes cluster.

  • Service YAML Example:

    apiVersion: v1
kind: Service
metadata:
  name: nodeport-web-service
spec:
  type: NodePort
  selector:
    app: web-app
  ports:
    - protocol: TCP
      port: 8082
      targetPort: 80
      nodePort: 30081

  • Explanation: The nodeport-web-service makes the pod accessible externally on TCP port 30081 on each node in the cluster.

5. Verifying Service Exposure

  • ClusterIP Verification: Use kubectl exec to access the web-app-pod from another pod within the cluster using the ClusterIP service.
  • NodePort Verification: Access the web-app-pod externally using <NodeIP>:30081, where NodeIP is the IP address of any node in the cluster.

6. Summary

  • Effective Use of Services: Understanding how to expose pods using ClusterIP and NodePort services is essential for application accessibility in Kubernetes.

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