Rsync is an open-source file synchronizing tool that provides incremental file transfer It can be used over insecure and secure transports (like SSH).  It is available on most Unix-based systems (such as macOS and Linux) and Windows. There are also GUI-based tools that use rsync, for example, Acrosync.

A basic command looks like this:

rsync [-options] SOURCE user@x.x.x.x:DESTINATION
  • -options is a dash followed by one or more letters, for example -v for verbose error messages, and -b to make backups. See the full list of options at the rsync man page. (Search for "Options summary.")
  • SOURCE is the path to the local file or directory that you want to copy or synchronize
  • user@ is the credentials of the user on the remote server you want to copy files over to.
  • x.x.x.x is the IP address of the remote server.
  • DESTINATION is the path to the location you want to copy your directory or files to on the remote server.

You can also make a connection over SSH using the -e option as shown:

rsync [-options] -e "ssh [SSH DETAILS GO HERE]" SOURCE user@x.x.x.x:DESTINATION

There are numerous examples on the Internet, including those at the official website, and at the Wikipedia entry for rsync.