NFSv3 Dynamic Provisioning Fails: Subdirectory Mount Not Supported

[ston3lu]

Summary

The driver claims to support NFSv3, but dynamic provisioning with NFSv3 fails due to a fundamental protocol limitation.

Problem

When using nfsvers=3 mount option, the driver attempts to mount subdirectories like:
mount -t nfs -o nfsvers=3 10.0.40.233:/x/pvc-8c532bdf-5405-4606-9021-0ef2abbbd32c /var/lib/kubelet/...

This always fails with:
mount.nfs: mounting 10.0.40.233:/x/pvc-8c532bdf-5405-4606-9021-0ef2abbbd32c failed, reason given by server: No such file or directory

Root Cause

NFSv3 protocol limitation: NFSv3 can only mount paths explicitly listed in /etc/exports. It cannot mount subdirectories of an exported path unless they are separately exported.

• If /etc/exports only contains /x, NFSv3 cannot mount /x/pvc-xxx
• NFSv4's pseudo-filesystem (with fsid=0) allows mounting subdirectories
• The driver's current design relies on NFSv4 semantics