[justsomeadvice0]

You might look at webdav instead, which has actual existing library implementations (unlike NFSv4), supports user/pass auth (in some cases you don't want wide-open services on loopback) and is based on HTTP; that would make the whole thing easier. Various projects offer a webdav combat layer, see cryptomator for one example: https://docs.cryptomator.org/en/latest/desktop/vault-mountin...

I went down the NFS road long ago - I somewhat (??) remember that coaxing macOS to mount_nfs on loopback is actually a PITA (I remember having to activate 127.0.0.* and mount 127.0.0.2).

[skissane]

I remember, around 10 years ago, mucking around with WebDAV, and discovering many WebDAV clients were extremely crapulent. Especially on Windows.

Maybe, some years later, Windows' WebDAV client has improved. And I can't remember whether macOS WebDAV was better or not.

[EdSchouten]

For Buildbarn I need to provide a writable file system that acts in a POSIX compliant way. I'm not convinced WebDAV could provide that.

[justsomeadvice0]

Fair point, agreed I doubt mount_webdav ends up posix compliant.