Lesson 11 Study Notes: Persistent Volumes and Persistent Volume Claims

Objective

Understand how Kubernetes provides persistent storage to Pods using:

• PersistentVolume (PV)
• PersistentVolumeClaim (PVC)
• Volume Mounts

Storage Flow

Host Directory (/mydata)
          ↑
PersistentVolume (PV)
          ↑
PersistentVolumeClaim (PVC)
          ↑
Pod
          ↑
/usr/share/nginx/html

Think of a PVC as a storage request and a PV as the actual storage resource.

What the Lab Demonstrated

1. Created a Persistent Volume

The PV pointed to a HostPath directory:

/mydata

This directory resides on the worker node and stores the data.

2. Created a Persistent Volume Claim

The PVC was bound to the PV:

PV  →  PVC

Once bound, a Pod can request storage through the PVC.

3. Mounted the Storage into an Nginx Pod

The Pod mounted the PVC at:

/usr/share/nginx/html

Anything written to this directory is actually written to the PV.

Proof that the Volume Worked

Inside the Pod:

kubectl exec -it test-pv-pod -- touch /usr/share/nginx/html/new

On worker1:

ls -l /mydata

Output showed:

hello
hellofile
hellofucker
new

This proves the Pod was writing data to the Persistent Volume.

Why This Matters

Containers are temporary.

If data is stored only inside a container filesystem:

Pod Deleted → Data Lost

If data is stored on a PV:

Pod Deleted → Data Remains

A new Pod can mount the same PVC and continue using the files.

The Missing Lab Step

The lab required creating:

/storage/index.html

containing:

hello lab11

Then verifying its existence from inside the Pod.

Create the File

kubectl exec -it test-pv-pod -- sh -c \
'echo "hello lab11" > /usr/share/nginx/html/index.html'

Verify the File Exists

kubectl exec -it test-pv-pod -- ls -l /usr/share/nginx/html

Verify the Contents

kubectl exec -it test-pv-pod -- cat /usr/share/nginx/html/index.html

Expected output:

hello lab11

Common Error Encountered

Error:

pod test-pv-pod does not have a host assigned

Cause:

persistentvolumeclaim "test-pv-claim" not found

The Pod could not be scheduled because the referenced PVC did not exist.

Fix:

• Create the missing PVC
• Or update the Pod to reference an existing PVC

Exam/Interview Takeaway

One-Sentence Summary

The purpose of the lab was to demonstrate that a Kubernetes Pod can write data to a Persistent Volume through a PVC, allowing the data to survive beyond the lifetime of the Pod.