Lab 03: Volume Management in OKS

• Create and use PersistentVolumes (PV) and PersistentVolumeClaims (PVC) with a StorageClass.
• Test volume behavior with simple applications.

Prerequisites

1. A running Kubernetes cluster provided by OKS.
2. Access to the kubectl CLI.
3. Administrator privileges on the cluster.
4. Basic knowledge of Kubernetes objects: Pod, PVC, etc.

Verify Cluster Access

Ensure you have the necessary permissions to access the target cluster. You must have a user or role that allows you to export or retrieve the cluster configuration.

Retrieve the kubeconfig file

oks-cli cluster kubeconfig --cluster-name my-cluster --project-name my-project > kubeconfig.yaml
export KUBECONFIG=./kubeconfig.yaml

Test the cluster

kubectl get nodes

Step 1: Verifying the Default StorageClass

Initial verification

OKS provides a default StorageClass for dynamic volumes. If you forget to create a custom StorageClass, Kubernetes will automatically use the default one. To check the available StorageClasses, run:

kubectl get storageclass

You should get a list of StorageClass like this:

NAME                PROVISIONER            RECLAIMPOLICY   VOLUMEBINDINGMODE      ALLOWVOLUMEEXPANSION   AGE
bsu-gp2 (default)   bsu.csi.outscale.com   Retain          WaitForFirstConsumer   true                   30d
bsu-gp2-del         bsu.csi.outscale.com   Delete          WaitForFirstConsumer   true                   30d
bsu-io1-50          bsu.csi.outscale.com   Retain          WaitForFirstConsumer   true                   30d
bsu-io1-50-del      bsu.csi.outscale.com   Delete          WaitForFirstConsumer   true                   30d
bsu-standard        bsu.csi.outscale.com   Retain          WaitForFirstConsumer   true                   30d
bsu-standard-del    bsu.csi.outscale.com   Delete          WaitForFirstConsumer   true                   30d

You can see that in the list of available StorageClass in our OKS cluster, the bsu-gp2 storage class is marked as the default (default). This means that when creating a PVC, if no storage class is specified, this one will be used automatically.

If you want to define another default storageClass, you can do it with:

kubectl patch storageclass bsu-gp2-del -p '{"metadata": {"annotations":{"storageclass.kubernetes.io/is-default-class":"true"}}}'

Step 2: Creating a ReadWriteOnce (RWO) PVC

Deploy a test environment

Create a dedicated namespace:

kubectl create namespace lab-volumes

Define the PVC

We will create a PersistentVolumeClaim (PVC) requesting 5 Gi of storage.

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: bsu-claim
  namespace: lab-volumes
spec:
  accessModes:
  - ReadWriteOnce
  resources:
    requests:
      storage: 5Gi
  storageClassName: bsu-standard

Apply the PVC

Apply the YAML file to create your PVC:

kubectl apply -f pvc.yaml

Once applied, you can verify that it has been created:

kubectl get pvc -n lab-volumes
NAME        STATUS    VOLUME   CAPACITY   ACCESS MODES   STORAGECLASS   VOLUMEATTRIBUTESCLASS   AGE
bsu-claim   Pending                                      bsu-standard   <unset>                 50s

You will notice that the STATUS is Pending, meaning it is not yet bound to a PersistentVolume. This is expected: the VOLUMEBINDINGMODE is WaitForFirstConsumer, so until a Pod uses this PVC, the PV will not be provisioned.

Step 3: Deploying a Pod Using the PVC

Define the Pod

Create a simple Pod that mounts the PVC and writes to a file:

apiVersion: v1
kind: Pod
metadata:
  name: app
  namespace: lab-volumes
spec:
  containers:
  - name: app
    image: centos:centos7
    command: ["/bin/sh"]
    args: ["-c", "while true; do echo $(date -u) >> /data/out.txt; sleep 5; done"]
    volumeMounts:
    - name: persistent-storage
      mountPath: /data
  volumes:
  - name: persistent-storage
    persistentVolumeClaim:
      claimName: bsu-claim

Apply the Pod

kubectl apply -f pod-rwo.yaml

Now the PVC should switch to Bound:

kubectl get pvc -n lab-volumes
NAME         STATUS   VOLUME                                    CAPACITY   ACCESS MODES   STORAGECLASS   AGE
bsu-claim    Bound    pvc-xxxx-xxxx-xxxx-xxxx                   5Gi        RWO            bsu-standard   5s

This means the PVC is now attached to a real volume.

Test the Pod

Check that the Pod is running:

kubectl get pods -n lab-volumes

Access it:

kubectl exec -it app -n lab-volumes -- /bin/sh

Check the file:

cat /data/out.txt

You should see timestamps every 5 seconds.

Follow live:

tail -f /data/out.txt

Apply external snapshotter CRDs

kubectl apply -f https://raw.githubusercontent.com/kubernetes-csi/external-snapshotter/release-8.0/client/config/crd/snapshot.storage.k8s.io_volumesnapshotclasses.yaml
kubectl apply -f https://raw.githubusercontent.com/kubernetes-csi/external-snapshotter/release-8.0/client/config/crd/snapshot.storage.k8s.io_volumesnapshotcontents.yaml
kubectl apply -f https://raw.githubusercontent.com/kubernetes-csi/external-snapshotter/release-8.0/client/config/crd/snapshot.storage.k8s.io_volumesnapshots.yaml
kubectl apply -f https://raw.githubusercontent.com/kubernetes-csi/external-snapshotter/release-8.0/deploy/kubernetes/snapshot-controller/rbac-snapshot-controller.yaml
kubectl apply -f https://raw.githubusercontent.com/kubernetes-csi/external-snapshotter/release-8.0/deploy/kubernetes/snapshot-controller/setup-snapshot-controller.yaml

Create a VolumeSnapshot

apiVersion: snapshot.storage.k8s.io/v1
kind: VolumeSnapshot
metadata:
  name: bsu-volume-snapshot
  namespace: lab-volumes
spec:
  volumeSnapshotClassName: csi-osc-vsc
  source:
    persistentVolumeClaimName: bsu-claim

Wait until ready

kubectl describe volumesnapshot.snapshot.storage.k8s.io bsu-volume-snapshot

Delete the application

kubectl delete pod app -n lab-volumes
kubectl delete pvc bsu-claim -n lab-volumes

Restore from snapshot

apiVersion: v1
kind: Pod
metadata:
  name: app
  namespace: lab-volumes
spec:
  containers:
  - name: app
    image: centos:centos7
    command: ["/bin/sh"]
    args: ["-c", "while true; do echo $(date -u) >> /data/out.txt; sleep 5; done"]
    volumeMounts:
    - name: persistent-storage
      mountPath: /data
  volumes:
  - name: persistent-storage
    persistentVolumeClaim:
      claimName: bsu-snapshot-restored-claim
---
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: bsu-snapshot-restored-claim
  namespace: lab-volumes
spec:
  accessModes:
    - ReadWriteOnce
  storageClassName: bsu-sc
  resources:
    requests:
      storage: 5Gi
  dataSource:
    name: bsu-volume-snapshot
    kind: VolumeSnapshot
    apiGroup: snapshot.storage.k8s.io

Validate data restoration

kubectl exec -it app -n lab-volumes -- /bin/sh
cat /data/out.txt

Cleanup

Delete all created resources.