Kf supports Kubernetes native NFS, and exposes them with a dedicated nfsvolumebroker service broker for developers to consume. This broker has an nfs service offering which has a service plan named existing.
Use kf marketplace to see the service offering:
$ kf marketplace
...
Broker Name Namespace Description
nfsvolumebroker nfs mout nfs shares
...
Use kf marketplace -s nfs to see the service plan:
$ kf marketplace -s nfs
...
Broker Name Free Description
nfsvolumebroker existing true mount existing nfs server
...
Requirements
You need an NFS volume that can be accessed by your Kubernetes cluster. Filestore is Google's managed NFS solution that provides access to clusters in the same gcloud project.
Prepare NFS
If you have an existing NFS service, you can use that. If you want a Google managed NFS service, create a Filestore instance and Kf will automaticlaly configure the cluster to use it.