Mastering Kubernetes Persistent Volumes: A Guide for Beginners | Day 36 of | 90DaysOfDevOps

Understanding Persistent Volumes in Kubernetes 🤔

In the Kubernetes world, Persistent Volumes provide a durable way to store data independently of Pods' lifecycles. Think of them as the secret keepers of your application's crucial data. 💾

Task 1: Adding Persistence to Your Todo App 📝

Let's dive into practicality! We'll enhance our Todo app by introducing a Persistent Volume. Follow these steps:

Step 1: Create a Persistent Volume (PV)

Start by creating a PV using a file on your node. Here's an example manifest (persistent-volume.yml):

apiVersion: v1
kind: PersistentVolume
metadata:
  name: mysql-pv-volume
  namespace: mysql
  labels:
    app: mysql
spec:
  capacity:
    storage: 2Gi
  accessModes:
    - ReadWriteOnce
  hostPath:
    path: "/path/on/your/node"

Apply the PV using kubectl apply -f persistent-volume.yml.

Step 2: Create a Persistent Volume Claim (PVC)

Now, create a PVC that references the PV. Example manifest (persistent-volume-claim.yml):

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: mysql-pv-claim
  namespace: mysql
spec:
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 1Gi

Apply the PVC using kubectl apply -f persistent-volume-claim.yml.

Step 3: Update Deployment Configuration

Update your deployment.yml to include the Persistent Volume Claim. Add the following snippet:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: todo-app-deployment
spec:
  replicas: 1
  selector:
    matchLabels:
      app: todo-app
  template:
    metadata:
      labels:
        app: todo-app
    spec:
      containers:
        - name: todo-app
          image: rishikeshops/todo-app
          ports:
            - containerPort: 8000
          volumeMounts:
            - name: todo-app-data
              mountPath: /app
      volumes:
        - name: todo-app-data
          persistentVolumeClaim:
            claimName: pvc-todo-app

Apply the updated deployment using:

kubectl apply -f deployment.yml

Step 4: Verification

Verify that the Persistent Volume has been added to your Deployment:

kubectl get pods
kubectl get pv

Task 2: Accessing Data in the Persistent Volume 🗂️

Now, let's connect to a Pod in your Deployment and ensure we can access the data stored in the Persistent Volume.

Step 1: Connect to a Pod

Use the command:

kubectl exec -it <pod-name> -- /bin/bash

Step 2: Verify Access

Inside the Pod, navigate to the mounted path (e.g., /app/data) and verify access to your data.

cd /app/data
ls

Congratulations! You've just added persistence to your Todo app in Kubernetes. 🎉

Conclusion:

🚀In this blog post, I learned how to add a persistent volume to a Node Todo app on Kubernetes. I learned how to create a PV resource, a PVC resource, a Deployment resource, and a Service resource for the Node Todo app. I also learned how to apply the manifests and verify the status of the resources on the Kubernetes cluster.

I hope you found this post useful and informative. If you have any questions or feedback, feel free to leave a comment below or reach out to me on LinkedIn or GitHub.

Thanks for reading and happy coding! 😊