To the surprise of many, OpenSSH actually comprises a suite of tools. We have already seen ssh, the secure shell command that connects to other machines, and sshd, the SSH server daemon that accepts incoming SSH connections. However, there is also sftp, a replacement for ftp, and scp, a replacement for rcp.
You should already be familiar with the ftp command because it is the lowest-common-denominator system for handling FTP file transfers. Like Telnet, though, ftp is insecure: It sends your data in plain text across the network and anyone can sniff your packets to pick out a username and password. The SSH replacement, sftp, puts FTP traffic over an SSH link, thus securing it.
The rcp command might be new to you, largely because it is not used much anymore. Back in its day, rcp was the primary way of copying a single file to another server. As with ftp, scp replaces rcp by simply channeling the data over a secure SSH connection. The difference between sftp and scp is that the former allows you to copy many files, whereas the latter just sends one.
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