FUSE (Filesystem in USErspace) implements a file system that is serviced by a userspace program.
The FUSE module has been worked on by several people:
AlanSomers overhauled the driver and added a test suite in 2019, sponsored by the FreeBSD Foundation.
As of 31-July-2019, the module implements version 7.23 of the FUSE protocol, with a few unimplemented features:
- flock(2) (implemented in-kernel, so it doesn't work for networked file systems)
- poll(2) (works for pipes and sockets, but not for regular files)
https://github.com/libfuse/libfuse Library used by many, but not all, FUSE file systems