More meant as a back up solution, it may also provide ways to sync files while going through a may be somewhat less trusted central server.
Ranked in these QuestionsQuestion Ranking
Pro Bandwidth and space efficient
Duplicity uses the rsync algorithm so only the changed parts of files are sent to the archive when doing an incremental backup. For instance, if a long log file increases by just a few lines of text, a small diff will be sent to and saved in the archive. Other backup programs may save a complete copy of the file.
Pro Encrypted locally before sending (using GnuPG)
Data is encrypted locally before being sent, and kept encrypted by a key that is never stored on the remote machine. So you might even store your data on a public space, people would still need your key or brute force it.
Pro Versioning and incremental backup
You can retrieve older versions or files you recently deleted locally even after having updated your backup.
Pro Works with scp/ssh, ftp, rsync, Amazon S3...
Duplicity does not make many demands on its archive server. As long as files can be saved to, read from, listed, and deleted from a location, that location can be used as a duplicity backend. Besides increasing choice for the user, it can make a server more secure, as clients only require minimal access.
Pro Free and open-source
Licensed under GNU GPL v2.
Pro Has a Dockerized image
Docker allows to run programs on any Linux without having to really install them, and allows to manage versions so it runs exactly the same on different machines.