The trick is to add environment variables to sudoers file via sudo visudo command and add these lines:
Defaults env_keep += "ftp_proxy http_proxy https_proxy no_proxy"
from: http://stackoverflow.com/questions/8633461/how-to-keep-environment-variables-when-using-sudoHow to keep Environment Variables when Using SUDO
原文：http://www.cnblogs.com/pinganzi/p/5947589.html