使用docker-machine create -d virtualbox创建主机，提示要更新但又由于网络的某些原因无法下载导致的错误如下：
Running pre-create checks...
(manager) Default Boot2Docker ISO is out-of-date, downloading the latest release...
(manager) Latest release for github.com/boot2docker/boot2docker is v1.11.2
(manager) Downloading C:\Users\Administrator\.docker\machine\cache\boot2docker.iso from https://github.com/boot2docker/boot2docker/releases/download/v
1.11.2/boot2docker.iso...
Error with pre-create check: "Get https://github-cloud.s3.amazonaws.com/releases/
...
解决办法：电脑断网