Recently I have been looking for a way to synchronise files between several machines, including my (OSX) laptop and a Linux-based network attached storage appliance. After looking at various alternatives, I settled on BitTorrent Sync, the file synchronisation system based on the BitTorrent file transfer protocol. This essentially works much like Dropbox (in that it automatically synchronises the contents of one or more directories between computers), only without there being a centralised server accessing or storing the data; synchronisation is done directly between peers, and the files are encrypted end to end.
One drawback of Dropbox (notwithstanding the still open question of privacy; can one prove that they're not compelled by secret directive to funnel everyone's documents to the NSA as they're uploaded, just in case?) has been the paucity of clients for more unusual systems, such as, for example, the NAS I mentioned. While it's fine for synchronising PCs, Macs and x86-based Linux boxes (their Linux client, whilst preferring a GUI, can be coaxed into working from the command line), it does not cover the new generation of lightweight servers and storage devices, which are often based on ARM CPUs. As I have such a server (a QNAP TS-412), I have been looking for a way to keep some files synchronised between it and other machines, including a MacBook running OSX. BitTorrent Sync seems to work quite nicely, though setting it up on the NAS box can require some thought.[...]