Answer by Archemar for Automatic and secure file transfer over two servers

you almost have it. user on server B must be given /bin/false as shell, this will forbid interactive login from server A (but file on server B can still be fetched or deleted).

Edit:

• using /bin/false as a shell forbid copying
• using /usr/sbin/nologin also (his account is currently not available.)

A more complex solution would involve vsftp (not ftps), but this require ssl certificates.