NFS-Ganesha

"NFS-Ganesha is a user-mode file server for NFS (v3, 4.0, 4.1, 4.1 pNFS, 4.2) and for 9P from the Plan9 operating system. It can support all these protocols concurrently.

NFS-Ganesha is an NFS version 2-4 server that runs in the user address space instead of as part of the operating system kernel. Filesystem in Userspace (FUSE) lets you run a filesystem in the user address space instead of as part of the Linux kernel, but the FUSE support in the Linux kernel from many Linux distributions does not allow you to export FUSE through NFS. NFS-GANESHA lets you expose FUSE through NFS without patching your kernel.

NFS-GANESHA accesses the underlying data through a File System Abstraction Layer (FSAL), allowing you to plug in your own storage mechanism and access it from any NFS client. NFS-GANESHA provides a FUSE-compatible FSAL to allow you to quickly access a FUSE filesystem over NFS while avoiding the need for data to bounce through the kernel FUSE mechanism on the NFS server."

https://github.com/nfs-ganesha/nfs-ganesha/wiki

https://github.com/cea-hpc/nfs-ganesha

https://www.linux.com/news/run-your-nfs-server-user-address-space-nfs-ganesha