Confira rsync
- que está fazendo exatamente isso.
Da página do manual:
Rsync is a fast and extraordinarily versatile file copying tool. It
can copy locally, to/from another host over any remote shell, or
to/from a remote rsync daemon. It offers a large number of options
that control every aspect of its behavior and permit very flexible
specification of the set of files to be copied. It is famous for its
delta-transfer algorithm, which reduces the amount of data sent over
the network by sending only the differences between the source files
and the existing files in the destination. Rsync is widely used for
backups and mirroring and as an improved copy command for everyday use.