How to Set and Verify the Default StorageClass in Kubernetes

Why Default StorageClass Matters

When a PersistentVolumeClaim (PVC) is created without specifying a

storageClassName

, Kubernetes automatically uses the default StorageClass to provision a volume, simplifying operations and ensuring consistency.

Set a Default StorageClass

Run the following command, replacing

<your-class-name>

with the desired StorageClass name:

<code>kubectl patch storageclass ceph-rbd-storage -p '{"metadata": {"annotations":{"storageclass.kubernetes.io/is-default-class":"true"}}}'
</code>

Tip: Replace

<your-class-name>

with the actual StorageClass name.

Verify the Default StorageClass

List the StorageClass to see which one is marked as default (indicated by

(default)

).

<code>kubectl get sc ceph-rbd-storage
NAME               PROVISIONER        RECLAIMPOLICY   VOLUMEBINDINGMODE   ALLOWVOLUMEEXPANSION   AGE
ceph-rbd-storage   (default) rbd.csi.ceph.com   Retain   Immediate   true   4d11h
</code>

Tip: The presence of

(default)

after the StorageClass name confirms it is the default.

Create and Test a PVC Using the Default StorageClass

1. Create a PVC without specifying a

storageClassName

:

<code>cat <<EOF | kubectl apply -f -
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: test-default-sc
  namespace: default
spec:
  accessModes:
  - ReadWriteOnce
  resources:
    requests:
      storage: 10Gi
EOF
</code>

2. Verify that the PVC is bound to the default StorageClass:

<code>kubectl get pvc test-default-sc
NAME               STATUS   VOLUME                                 CAPACITY   ACCESS MODES   STORAGECLASS       AGE
test-default-sc    Bound    pvc-1423da19-d267-49cc-92cc-7117a7f9a956   10Gi      RWO            ceph-rbd-storage   6s
</code>

Reference Articles

https://kubernetes.io/zh-cn/docs/concepts/storage/storage-classes/#default-storageclass

https://kubernetes.io/zh-cn/docs/tasks/administer-cluster/change-default-storage-class/

Conclusion

The default StorageClass is a key component of Kubernetes storage management; configuring it properly can greatly improve efficiency and flexibility.