简化Docker安装的命令行工具：Docker Machine

Docker Machine是一个简化Docker安装的命令行工具，通过一个简单的命令行即可在相应的平台上安装Docker，比如VirtualBox、 Digital Ocean、Microsoft Azure。

使用过程：

$ docker-machine create -d virtualbox dev  INFO[0000] Creating SSH key...  INFO[0000] Creating VirtualBox VM...  INFO[0007] Starting VirtualBox VM...  INFO[0007] Waiting for VM to start...  INFO[0041] "dev" has been created and is now the active machine.  INFO[0041] To point your Docker client at it, run this in your shell: $(docker-machine env dev)     $ docker-machine ls  NAME   ACTIVE   DRIVER       STATE     URL                         SWARM  dev    *        virtualbox   Running   tcp://192.168.99.127:2376     $ $(docker-machine env dev)     $ docker run busybox echo hello world  Unable to find image 'busybox:latest' locally  511136ea3c5a: Pull complete  df7546f9f060: Pull complete  ea13149945cb: Pull complete  4986bf8c1536: Pull complete  hello world     $ docker-machine create -d digitalocean --digitalocean-access-token=secret staging  INFO[0000] Creating SSH key...  INFO[0001] Creating Digital Ocean droplet...  INFO[0002] Waiting for SSH...  INFO[0070] Configuring Machine...  INFO[0109] "staging" has been created and is now the active machine.  INFO[0109] To point your Docker client at it, run this in your shell: $(docker-machine env staging)     $ docker-machine ls  NAME      ACTIVE   DRIVER         STATE     URL                          SWARM  dev                virtualbox     Running   tcp://192.168.99.127:2376  staging   *        digitalocean   Running   tcp://104.236.253.181:2376