ckad练习题-State Persistence

State Persistence (8%)

Defining and Mounting a PersistentVolume

1. Create a Persistent Volume named pv, access mode ReadWriteMany, storage class name shared, 512MB of storage capacity and the host path /data/config.
2. Create a Persistent Volume Claim named pvc that requests the Persistent Volume in step 1. The claim should request 256MB. Ensure that the Persistent Volume Claim is properly bound after its creation.
3. Mount the Persistent Volume Claim from a new Pod named app with the path /var/app/config. The Pod uses the image nginx.
4. Check the events of the Pod after starting it to ensure that the Persistent Volume was mounted properly.

Solution:

Create a YAML file for the Persistent Volume and create it with the command kubectl create command.

apiVersion: v1
kind: PersistentVolume
metadata:
  name: pv
spec:
  capacity:
    storage: 512m
  accessModes:
    - ReadWriteMany
  storageClassName: shared
  hostPath:
    path: /data/config

You will see that the Persistent Volume has been created but and is available to be claimed.

$ kubectl get pv
NAME   CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS      CLAIM   STORAGECLASS   REASON   AGE
pv     512m       RWX            Retain           Available           shared                  4s

Create a YAML file for the Persistent Volume Claim and create it with the command kubectl create command.

kind: PersistentVolumeClaim
apiVersion: v1
metadata:
  name: pvc
spec:
  accessModes:
    - ReadWriteMany
  resources:
    requests:
      storage: 256m
  storageClassName: shared

You will see that the Persisten Volume Claim has been created and has been bound to the Persisten Volume.

$ kubectl get pvc
NAME   STATUS   VOLUME   CAPACITY   ACCESS MODES   STORAGECLASS   AGE
pvc    Bound    pv       512m       RWX            shared         2s

$ kubectl get pv
NAME   CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS   CLAIM         STORAGECLASS   REASON   AGE
pv     512m       RWX            Retain           Bound    default/pvc   shared                  1m

Create a YAML file for the Pod and create it with the command kubectl create command.

apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: null
  labels:
    run: app
  name: app
spec:
  containers:
  - image: nginx
    name: app
    volumeMounts:
      - mountPath: "/var/app/config"
        name: configpvc
    resources: {}
  volumes:
    - name: configpvc
      persistentVolumeClaim:
        claimName: pvc
  dnsPolicy: ClusterFirst
  restartPolicy: Never
status: {}

You can check the events of a Pod with the kubectl describe command. You should see an entry that indicates the successful mount.

$ kubectl describe pod app
...
Events:
  Type    Reason                 Age   From                         Message
  ----    ------                 ----  ----                         -------
  Normal  Scheduled              16s   default-scheduler            Successfully assigned app to docker-for-desktop
  Normal  SuccessfulMountVolume  16s   kubelet, docker-for-desktop  MountVolume.SetUp succeeded for volume "pv"
  Normal  SuccessfulMountVolume  16s   kubelet, docker-for-desktop  MountVolume.SetUp succeeded for volume "default-token-fsmmp"
  Normal  Pulling                15s   kubelet, docker-for-desktop  pulling image "nginx"
  Normal  Pulled                 14s   kubelet, docker-for-desktop  Successfully pulled image "nginx"
  Normal  Created                14s   kubelet, docker-for-desktop  Created container
  Normal  Started                13s   kubelet, docker-for-desktop  Started container