ProFTPD: Supported FTP Commands

Supported FTP Commands

Supported SITE commands

Unsupported FTP Commands

Frequently Asked Questions

Question: I can use the RNFR and RNTO commands to move a file, even across different disks/mount points. And I can use RNFR/RNTO to move a directory, but I cannot move a directory across different disks/mount points. Is this a bug?
Answer: No, it is not a bug. Why not? Ultimately, it is because the FTP specifications do not guarantee (or even discuss) that an FTP implementation must support renaming of directories across mount points.

ProFTPD implements the RNFR/RNTO functionality by using the rename(2) system call. And rename(2) is documented to not work across mount points.

"But then why does it work when I rename a file across mount points?" you ask. Good question. The answer is that for files only, ProFTPD detects the rename(2) error for renaming across mount points, and then copies the file in question to the new location, deleting the old location when the copy completes successfully.

"Great!" you say, "Now do the same thing for directories!" Unfortunately, for directories, the answer is not that simple. Here are some things to consider when copying directories: what if the directory contains sockets, FIFOs, devices, and other irregular file types which cannot be easily copied/moved? Should copying/moving of directories automatically use root privileges in order to preserve the ownership on files that do not belong to the logged-in user? What if the copying/deleting of files fails in the midde: what should then happen to the copied (and remaining) files/directories?

Since there are no easy answers as yet to the above questions, ProFTPD now detects the rename(2) error for renaming across mount points for a directory, and rejects the RNTO command, showing something like:

  RNFR directory
  350 File or directory exists, ready for destination name
  RNTO /other/mount/directory
  550 Rename /other/mount/directory: Is a directory
That "Is a directory" error indicates that ProFTPD cannot rename a directory across the mount points you requested. (That particular error message can, and will, be made more informative.)

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