scp as a volume conduit?
We are currently able to use rsync to synchronise between the host and the machines. However, this relies on rsync to get a proper ssh command working and the ability to install rsync in the boot2docker image. Adding the type scp to shares would allow to get rid of those limitations and ensure that machinery is able to synchronise (albeit... slowly) between the host and the machines whichever distribution they run.
One way to mitigate this would be to use the new OS type discovery mechanisms introduced in f0896b32740279c582e56902a4a0bc2c2b6a9806 to detect the type of the remote machine and install rsync using the various package managers that are available (apt-get, zypper, etc.)