I've been playing around with Ethereum Blockchain and one of the first steps to test your network is to build your docker image.
Even though Docker Machine is a great tool, has some issues.
I ran my test on my MacBook Pro and one of the steps required to build your docker instance is to run the
docker-compose up command to build your custom machine, however during the building process I got the following error message:
ERROR: Couldn't connect to Docker daemon - you might need to run docker-machine start default.
In order to overcome this problem you must run the following command
eval "$(docker-machine env default)"
And that's it. You should be able to build your machine with the docker-compose command.