Docker Machine allows you to create and manage virtual machines, using a driver, and deploying a small Linux-based OS that has Docker pre-installed.
What size?
du -h ~/.docker/machine/machines/host-1/
76K /Users/joaofernandes/.docker/machine/machines/host-1//host-1/Logs
92K /Users/joaofernandes/.docker/machine/machines/host-1//host-1
388M /Users/joaofernandes/.docker/machine/machines/host-1/
But if you’re already running Ubuntu, maybe you don’t need Docker Machine, since you can install Docker directly on Ubuntu. Most people using Docker Machine were doing it to run Docker on a Mac or Windows, and now you can use Docker for Mac and Docker for Windows.