nfs provisioner too old and needs an update

[Shunde Zhang]

I followed this page [1] to set up nfs with my k8s 1.25.
However the nfs client provisioner is too old and deprecated.
When creating a pvc, it is always pending.
Checking the provisioner log, it is complaining about selfLink being empty.

E0331 06:53:31.562497 1 controller.go:1004] provision "controller-myk8scloud/storage-controller-0" class "default": unexpected error getting claim reference: selfLink was empty, can't make reference

This issue [2] suggests we can fix that by adding "--feature-gates=RemoveSelfLink=false" to apiserver.
But the value RemoveSelfLink is always true from 1.24 [3][4] and can't be set to false.
So according to some comments of [2] I changed to "gcr.io/k8s-staging-sig-storage/nfs-subdir-external-provisioner:v4.0.0", which fixed the issue.
It seems nfs-subdir-external-provisioner is the replacement of nfs-client-provisioner [5]

My deployment looks like [6], and my storage class is like [7].
Please update templates/nfs-provisioner.yaml to use the new nfs-subdir-external-provisioner for k8s 1.24+.

[1] https://ubuntu.com/kubernetes/docs/storage
[2] https://github.com/kubernetes-sigs/nfs-subdir-external-provisioner/issues/25
[3] https://kubernetes.io/docs/reference/command-line-tools-reference/feature-gates/
[4] https://github.com/kubernetes/enhancements/blob/master/keps/sig-api-machinery/1164-remove-selflink/README.md
[5] https://github.com/kubernetes-sigs/nfs-subdir-external-provisioner
[6] https://pastebin.ubuntu.com/p/CchMMmySgk/
[7] https://pastebin.ubuntu.com/p/X6hX3WxfGj/

[George Kraft (cynerva)]

Indeed, the nfs provisioner in kubernetes-worker is ancient and poorly maintained. The nfs-subdir-external-provisioner that you deployed seems like a fine replacement. I suspect that the NFS CSI driver[1] might be a better long term solution.

I also think that kubernetes-worker should not be responsible for this. I recommend we deprecate the NFS provisioner in kubernetes-worker and replace it with a better alternative (maybe a new charm) that deploys an external NFS provisioner.

[1]: https://github.com/kubernetes-csi/csi-driver-nfs