rrsync (restricted rsync) is a helper script for setting up restricted
rsync users via ssh logins.  Used as a command="rrsync DIR" prefix on
a key in a user's ~/.ssh/authorized_keys file, it confines any rsync
transfer made with that key to the declared subdirectory, optionally
read-only (-ro) or write-only (-wo), and rejects rsync options that
would allow escaping the restriction.

Homepage:
https://rsync.samba.org/
