Monitor directories for changes and file sync

Question

Anyone know a small and lightweight program to monitor a directory for changes in the background and file sync these to a remote server?

A little bit like Dropbox, but I wan't it to be able to specify exactly what directories and where that specific directory should sync to via SCP/FTP/REST API or anything like that to a remote system.

It should run in the background 24/7, so not a "Windows Commander" type of application that monitors and syncs when it is open.

Windows and Linux support required.

Answer 1

I use BitTorrent Sync from resilio: https://www.resilio.com/individuals/ Free version works very well, has clients for Windows, Mac, Linux, iOS, Android and even Network Attached Storages.

Answer 2

Syncthing would be good option as it is free, secure and open source. It supports Windows, Mac, Linux and Android.