httpd and nfsd can not read usb external storage

Mac mini m4, macOS Sequoia apache httpd webdav nfs Both httpd and nfsd work well when I share a directory on internal storage like /Users/abc/share. When I share a directory on usb external storage like /Volumes/udisk/share, both httpd and nfsd raised errors like "can not read /Volumes/udisk/share" and "not permitted". The exteranl storage file system is APFS. The owner user:group of /Volumes/udisk/share is abc:staff, the same as /Users/abc/share, and file mode is 777. The only difference is internal/external storage. Does accessing external storage require additional authorization? How can I resolve this issue? Any suggestions would be greatly appreciated.