Keep a folder in sync on several hosts using a central server. Heavily inspired by DropBox.

Initialize a server repository:

ssh server.example.com
mkdir repo.mf; cd repo.mf
mf init -s

Initialize a client repository:

mf init server.example.com:repo.mf

Synchronize:

mf sync

The server keeps a list of incremental versions (file metadata) and a hashed blob store (file contents). Clients synchronize by uploading local changes, the server appends them to its version history, and sends back a list of changes made by other clients.

Synchronization happens over SSH and is invoked manually. Don't think about touching any file during a sync because you will lose your data.

Usually files will be smoothly added and removed by clients, but if there is a conflict, MagicFolder will rename one of the versions. You should best know to solve the conflict; when you're done, simply remove the extra file.

While MagicFolder is intended to back up data by replicating on several hosts, and the author uses it routinely, be warned it's alpha-quality. In particular there is no provision for detecting changes to files during synchronization or recovering from errors. The client-server chatter protocol is also in flux, so be sure to use the same version of MagicFolder on both client and server.