The "site chkhash" [md5digest] extension
This command allows an FTP client to register an MD5 hash digest with the server so that the content-hash of the next uploaded file can be checked before the file is committed to the NetStorage area. If the hash values do not match, the transfer attempt returns an error. If there is some other error during transfer, the hash string is discarded and must be re-registered before retrying the upload.
ftp> quote "site chkhash 0123ab456789c012345d6ef7890g12h3" 200 Hash check set to 0123ab456789c012345d6ef7890g12h3
site az2zcommand. Doing so will cause an error, as the
site az2zcommand adds information to the archive, which will cause the MD5 checksum to fail.