Now that we have discussed how to launch individual Docker instances using Docker Machine, let's get a little more adventurous and create a cluster of instances. To do this, Docker ships a tool called Swarm. When deployed, it acts as a scheduler between your Docker client and host Docker instances, deciding where to launch containers based on scheduling rules.
To start off, we are going to be using Docker Machine to create a cluster locally using VirtualBox (https://www.virtualbox.org), which is bundled with Docker Toolbox. To start, we are going to launch a VM to generate a discovery token. To do this, run the following commands:
docker-machine create -d virtualbox discover
Then configure your Docker client ...