Practice Test - Persistent Volumes and Persistent Volume Claims

ㅁ We have deployed a POD. Inspect the POD and wait for it to start running. In the current(default) namespace.

kubectl get pod

 

ㅁ The application stores logs at location /log/app.log. View the logs.

You can exec in to the container and open the file: 

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

 

ㅁ If the POD was to get deleted now, would you be able to view these logs.

apiVersion: v1
kind: Pod
metadata:
  name: webapp
  namespace: default
spec:
  containers:
  - image: kodekloud/event-simulator
    name: webapp
    volumeMounts:
    - mountPath: /log
      name: webapp-log
  volumes:
  - name: webapp-log
    hostPath:
      path: /var/log/webapp
      type: Directory

 

ㅁ Create a persistent Volume with the given specification.

- Volume Name: pv-log

- Storage: 100Mi

- Access Modes: ReadWriteMany

- Host Path: /pv/log

apiVersion: v1
kind: PersistentVolume
metadata:
  name: pv-log
spec:
  storageClassName: ""
  capacity:
    storage: 100Mi
  volumeMode: Filesystem
  accessModes:
    - ReadWriteMany
  hostPath:
    path: /pv/log

ㅁ Let us claim some of that storage for our application. Create a Persistent Volume Claim with the given specification

- Volume Name: claim-log-1

- Storage Request: 50Mi

- Access Modes: ReadWriteOnce

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

ㅁ What is the state of the Persistent Volume Claim?

$ kubectl get pvc

NAME          STATUS    VOLUME   CAPACITY   ACCESS MODES   STORAGECLASS   AGE
claim-log-1   Pending                                                     109s

ㅁ What is the state of the Persistent Volume?

$ kubectl get pv

NAME     CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS      CLAIM   STORAGECLASS   REASON   AGE
pv-log   100Mi      RWX            Retain           Available                                   5m22s

ㅁ Why is the claim not bound to the available Persitent Volume?

[Reclaim Policy not set correctly]

[Capacity Mismatch]

[Access Modes Mismatch]

[PV and PVC name mismatch]

 

ㅁ You requested for 50Mi, how much capacity is now available to the PVC?

$ kubectl get pvc
NAME          STATUS   VOLUME   CAPACITY   ACCESS MODES   STORAGECLASS   AGE
claim-log-1   Bound    pv-log   100Mi      RWX                           6s

 

ㅁ Update the Access Mode on the claim to bind it to the PV

아래와 같이 yaml 수정 후 재배포(delete and create)

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

$ kubectl get pvc
NAME          STATUS   VOLUME   CAPACITY   ACCESS MODES   STORAGECLASS   AGE
claim-log-1   Bound    pv-log   100Mi      RWX                           7s

 

ㅁ Update the webapp pod to use the persistent volume claim as its storage. Replace hostPath configured earlier with the newly created PersistentVolumeClaim.

- Name: webapp

- Image NAme: kodekloud/event-simulator

- Volume: PersistentVolumeClaim=claim-log-1

- Volume Mount: /log

apiVersion: v1
kind: Pod
metadata:
  name: webapp
spec:
  containers:
  - name: webapp
    image: kodekloud/event-simulator
    volumeMounts:
    - mountPath: /log
      name: webapp-log
  volumes:
  - name: webapp-log
    persistentVolumeClaim:
      claimName: claim-log-1

$ touch /pv/log/pvc-test

$ kubectl exec webapp -- ls /log
app.log
pvc-test

ㅁ What is the Reclaim Policy set on the Persistent Volume pv-log?

$ kubectl describe pv pv-log

Name:            pv-log
Labels:          <none>
Annotations:     pv.kubernetes.io/bound-by-controller: yes
Finalizers:      [kubernetes.io/pv-protection]
StorageClass:    
Status:          Bound
Claim:           default/claim-log-1
Reclaim Policy:  Retain
Access Modes:    RWX
VolumeMode:      Filesystem
Capacity:        100Mi
Node Affinity:   <none>
Message:         
Source:
    Type:          HostPath (bare host directory volume)
    Path:          /pv/log
    HostPathType:  
Events:            <none>

 

 

ㅁ Try deleting the PVC and notice what happens

$ kubectl delete pvc claim-log-1

[The PVC is delete]

[The PVC is stuck in 'terminating' state]

 

ㅁ Why is the PVC stuck in Terminating state?

 

[The PVC is being used by a POD]

[The PVC is wating for the PV to be deleted]

[The PVC is in the process of scrubbing]

 

 

ㅁ Let us now delete the webapp Pod. Once deleted, wait for the pod to fully terminate.

kubectl delete pod webapp

ㅁ What is the state of the PVC now?

kubectl get pvc

[Deleted]

 

ㅁ What is the state of the Persistent Volume now?

kubectl get pv

[Release]