APFS sparse bundle on SMB: rsync "Operation not supported (45)" and F_FULLFSYNC
rsync into an encrypted APFS sparse bundle stored on an SMB share failed on every write with error 45. The files were fine. APFS inside the image needs F_FULLFSYNC on the band files, the NAS's SMB server doesn't support it, and a short Python probe proves it.
·4 mins