U
Udoh Deborah
Guest
On Day 36 of your #90DaysOfDevOps journey, weβre tackling an important part of Kubernetes: Persistent Volumes (PVs)
Letβs break this down and walk you through both tasks:
What are Persistent Volumes (PV) in Kubernetes?
Kubernetes Pods are ephemeral β which means data inside a Pod is lost when the Pod is deleted or restarted. To persist data beyond the lifecycle of a Pod, we use:
β’ Persistent Volumes (PV): Storage resource in the cluster, provisioned by admins or dynamically via StorageClass.
β’ Persistent Volume Claims (PVC): A request for storage by a user or app.
β’ Deployment + PVC: Your app (e.g., the ToDo app) can claim storage by referencing a PVC.
Task 1: Add Persistent Volume to Your Deployment
Letβs go step-by-step.
apiVersion: v1
kind: PersistentVolume
metadata:
name: todo-pv
spec:
capacity:
storage: 1Gi
accessModes:
- ReadWriteOnce
hostPath:
path: /mnt/data
This creates a 1Gi volume using the hostPath /mnt/data on the node (local path for testing).
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
name: todo-pvc
spec:
accessModes:
- ReadWriteOnce
resources:
requests:
storage: 1Gi
This PVC will bind to the todo-pv if the specs match.
Hereβs the updated Deployment with volume mounting:
apiVersion: apps/v1
kind: Deployment
metadata:
name: todo-app
spec:
replicas: 1
selector:
matchLabels:
app: todo
template:
metadata:
labels:
app: todo
spec:
containers:
- name: todo-container
image: your-todo-app-image
volumeMounts:
- name: todo-storage
mountPath: /app/data
volumes:
- name: todo-storage
persistentVolumeClaim:
claimName: todo-pvc
Make sure:
β’image: your-todo-app-image is replaced with your actual image.
β’/app/data is where your app stores persistent data.
kubectl apply -f pv.yml
kubectl apply -f pvc.yml
kubectl apply -f deployment.yml
kubectl get pv
kubectl get pvc
kubectl get pods
Look for STATUS: Bound on the PVC and Running pods.
Task 2: Access Data Inside the Pod
kubectl get pods # get pod name
kubectl exec -it -- /bin/bash
cd /app/data
ls -l
cat
You should see files created or used by your app.
Optional: Test Persistence
1. Delete the pod:
kubectl delete pod
You have Created and attached a Persistent Volume.
Continue reading...
Letβs break this down and walk you through both tasks:
What are Persistent Volumes (PV) in Kubernetes?
Kubernetes Pods are ephemeral β which means data inside a Pod is lost when the Pod is deleted or restarted. To persist data beyond the lifecycle of a Pod, we use:
β’ Persistent Volumes (PV): Storage resource in the cluster, provisioned by admins or dynamically via StorageClass.
β’ Persistent Volume Claims (PVC): A request for storage by a user or app.
β’ Deployment + PVC: Your app (e.g., the ToDo app) can claim storage by referencing a PVC.
Task 1: Add Persistent Volume to Your Deployment
Letβs go step-by-step.
- Create a Persistent Volume (pv.yml)
apiVersion: v1
kind: PersistentVolume
metadata:
name: todo-pv
spec:
capacity:
storage: 1Gi
accessModes:
- ReadWriteOnce
hostPath:
path: /mnt/data
This creates a 1Gi volume using the hostPath /mnt/data on the node (local path for testing).
- Create a Persistent Volume Claim (pvc.yml)
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
name: todo-pvc
spec:
accessModes:
- ReadWriteOnce
resources:
requests:
storage: 1Gi
This PVC will bind to the todo-pv if the specs match.
- Update your deployment.yml to use the PVC
Hereβs the updated Deployment with volume mounting:
apiVersion: apps/v1
kind: Deployment
metadata:
name: todo-app
spec:
replicas: 1
selector:
matchLabels:
app: todo
template:
metadata:
labels:
app: todo
spec:
containers:
- name: todo-container
image: your-todo-app-image
volumeMounts:
- name: todo-storage
mountPath: /app/data
volumes:
- name: todo-storage
persistentVolumeClaim:
claimName: todo-pvc
Make sure:
β’image: your-todo-app-image is replaced with your actual image.
β’/app/data is where your app stores persistent data.
- Apply the files
kubectl apply -f pv.yml
kubectl apply -f pvc.yml
kubectl apply -f deployment.yml
- Verify Everything
kubectl get pv
kubectl get pvc
kubectl get pods
Look for STATUS: Bound on the PVC and Running pods.
Task 2: Access Data Inside the Pod
- Connect to the Pod
kubectl get pods # get pod name
kubectl exec -it -- /bin/bash
- Verify Data Access
cd /app/data
ls -l
OR
cat
You should see files created or used by your app.
Optional: Test Persistence
1. Delete the pod:
kubectl delete pod
Code:
2. A new pod will be created (Deployment ensures this).
3. Check if data is still present by repeating the steps to access /app/data.You have Created and attached a Persistent Volume.
Continue reading...
