Simple btsync docker build. This image just installs a btsync executable with no configuration in /opt/ and runs it as the entry point. Therefore a configuration should be shared as a volume (normally /opt/btsync.conf). At a minimum, the configuration should specify a device name and a non-random listening port (since the port needs to be exposed by docker). Remember to mount a persistent storage directory (normally /opt/.sync). Clearly, the actual shared directory or directories should also be mounted as persistent storage directories.