Versão MacOS : 10.13.6
Oracle VM : Versão 6.1.18 r142142 (Qt5.6.3)
Instalei o docker-machine pelo :
https://github.com/Nordstrom/docker-machine/blob/master/docs/install-machine.md
> docker-machine version
docker-machine version 0.5.5, build 02c4254
learning-docker on master [!?]
> docker-machine create --driver virtualbox default
Error loading driver "virtualbox": Error attempting to get plugin server address for RPC: Failed to dial the plugin server in 10s
learning-docker on master [!?]