What is the purpose of the `scp` command?

The purpose of the scp command is to securely copy files between hosts. It utilizes the SSH (Secure Shell) protocol to ensure that the data being transferred is encrypted, providing confidentiality and security during the transmission. This makes scp particularly useful when transferring files over potentially unsecured networks, as it protects against eavesdropping and man-in-the-middle attacks.

The command allows users to specify the source and destination for the file transfer, which can include local files as well as files on remote servers. This flexibility and security make scp a go-to tool for securely transferring files across different machines.

In contrast, the other options refer to different functionalities that are not encompassed by scp. Archiving directories typically involves using commands like tar to bundle files, while synchronizing files is often done using tools like rsync that can optimize bandwidth by only transferring changed portions of files. Backup system data involves creating snapshots or copies that may not necessarily utilize the secure, direct transfer features that scp provides.