Editing Ceph-CSI Provisioner for Kubernetes (section)

==== Default Storage Class (Optional) ====
Not all manifests specify a storage class -- this can be especially problematic with helm charts that don't expose the opportunity to specify a storage class.  Kubernetes has the concept of a '''default''' storage class that is widely used by the cloud providers to point to their preferred storage solution.  While not required, specifying a Rook StorageClass as default can simplify 'automatic' deployments.  In reality, all that needs to be done is to set a flag on the storage class that you want to be default ... but there's some prep work ...

First, identify all the defined storage classes:

 kubectl get sc

All the storage classes will be shown -- if one of them is already defined as a 'default' class, it will have '''(default)''' after the name.  If there is a default class identified (and it isn't yours) you need to turn off the default status for that class (i.e. setting a new default does NOT reset the old default):

 kubectl patch storageclass <old-default> -p '{"metadata": {"annotations":{"storageclass.kubernetes.io/is-default-class":"false"}}}'

Then you can set your storageclass as the default:

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

Validate that it took by looking at the storageclasses again:

 kubectl get sc

Your class should now be marked '(default)'.

(excerpted from https://kubernetes.io/docs/tasks/administer-cluster/change-default-storage-class/)