1. 准备环境：
- Git Bash
- Docker Tool Box
- Windwos 7
2. 错误症状：
>$ docker pull registry:2
Pulling repository docker.io/library/registry
Network timed out while trying to connect to https://index.docker.io/v1/repositories/library/registry/images. You may want to check your internet connection or if you are behind a proxy.
3. 解决办法：
- docker-machine ssh virtual_box
- 找到 /var/lib/boot2docker/profile
- 修改Export
* export HTTP_PROXY=http://proxy:port
* export HTTPS_PROXY=http://proxy:port
- 重启环境 docker-machine restart virtual_box
