Solution Persistent Volumes and Persistent Volume Claims optional

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Step 1. Viewing Application Logs

kubectl exec webapp -- cat /log/app.log

kubectl get pods

NAME    READY   STATUS    RESTARTS   AGE
webapp  1/1     Running   0          107s

kubectl describe pod webapp

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Step 2. Configuring a HostPath Volume

1. Verify that the host directory /var/log/webapp is empty:
   ls /var/log/webapp
   
2. Edit the pod manifest to add a new volume. Run:
   kubectl edit pod webapp
   
3. In the pod specification, locate the volumes: section (currently showing only the kube API access volume) and add a new volume for logs. For example:
   apiVersion: v1
   kind: Pod
   metadata:
     name: webapp
     namespace: default
   spec:
     containers:
     - name: event-simulator
       image: kodekloud/event-simulator
       env:
         - name: LOG_HANDLERS
           value: file
       volumeMounts:
         - name: kube-api-access-lmntb
           mountPath: /var/run/secrets/kubernetes.io/serviceaccount
           readOnly: true
         - name: log-volume
           mountPath: /log
     volumes:
     - name: log-volume
       hostPath:
         path: /var/log/webapp
     - name: kube-api-access-lmntb
       projected:
         defaultMode: 420
         sources:
         - serviceAccountToken:
             path: token
             expirationSeconds: 3607
   
4. If you encounter an error about immutable fields when saving the changes, save the modified manifest to a temporary file and force-replace the pod:
   kubectl replace --force -f /tmp/kubectl-edit-298569051.yaml
   

cat /var/log/webapp/app.log

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Step 3. Creating a Persistent Volume (PV)

apiVersion: v1
kind: PersistentVolume
metadata:
  name: pv-log
spec:
  capacity:
    storage: 100Mi
  accessModes:
    - ReadWriteMany
  persistentVolumeReclaimPolicy: Retain
  hostPath:
    path: /pv/log

1. Save the above manifest to a file named pv.yaml.
2. Create the persistent volume:
   kubectl create -f pv.yaml
   
3. Verify the PV creation:
   kubectl get pv
   

NAME     CAPACITY   ACCESS MODES    RECLAIM POLICY   STATUS      CLAIM   STORAGECLASS   AGE
pv-log   100Mi      ReadWriteMany   Retain           Available           <none>         3s

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Step 4. Creating a Persistent Volume Claim (PVC)

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: claim-log-1
spec:
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 50Mi

1. Save this content to a file named pvc.yaml.

2. Apply the PVC manifest:
   kubectl create -f pvc.yaml
   
3. Check the PVC status:
   kubectl get pvc
   

NAME          STATUS   VOLUME   CAPACITY   ACCESS MODES   STORAGECLASS   AGE
claim-log-1   Pending

4. Verify that the PV remains available:
   kubectl get pv pv-log
   

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: claim-log-1
spec:
  accessModes:
    - ReadWriteMany
  resources:
    requests:
      storage: 50Mi

5. Force replace the PVC with the updated configuration:
   kubectl replace --force -f pvc.yaml
   
6. Recheck the PVC status. It should now be bound to the PV with the appropriate capacity.

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Step 5. Updating the Pod to Use the PVC

1. Edit the pod manifest to remove the HostPath volume and replace it with the PVC reference. Use the following snippet for guidance:
   apiVersion: v1
   kind: Pod
   metadata:
     name: webapp
     namespace: default
   spec:
     containers:
     - name: event-simulator
       image: kodekloud/event-simulator
       env:
         - name: LOG_HANDLERS
           value: File
       volumeMounts:
         - name: kube-api-access-lmntb
           mountPath: /var/run/secrets/kubernetes.io/serviceaccount
           readOnly: true
         - name: log-volume
           mountPath: /log
     volumes:
     - name: log-volume
       persistentVolumeClaim:
         claimName: claim-log-1
     - name: kube-api-access-lmntb
       projected:
         defaultMode: 420
         sources:
           - serviceAccountToken:
               expirationSeconds: 3607
               path: token
   
2. Force replace the pod with the updated manifest:
   kubectl replace --force -f <updated-pod-manifest-file.yaml>
   
3. Confirm that application logs are being written to the persistent storage on the host. For example:
   cat /pv/log/app.log
   

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Step 6. Verifying Reclaim Policy and Cleanup Behavior

kubectl get pv pv-log

NAME     CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS   CLAIM                  STORAGECLASS   AGE
pv-log   100Mi      RWX            Retain           Bound    default/claim-log-1    <none>         9m47s

1. Delete the PVC:
   kubectl delete pvc claim-log-1
   
2. In a separate terminal or after a moment, verify the PVC status:
   kubectl get pvc
   
   The PVC might display a “Terminating” status if the volume is still in use.
3. Once the PVC is removed, check the PV status:
   kubectl get pv pv-log
   

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Lab Summary

1. Viewed application logs inside a pod.
2. Configured a HostPath volume for log persistence.
3. Created a PersistentVolume (PV) and a corresponding PersistentVolumeClaim (PVC).
4. Updated the pod configuration to use the PVC.
5. Verified the reclaim policy behavior, ensuring that a PV with a “Retain” policy remains available even after deleting the PVC.