http://technoblog.org/2009/07/configure-apt-get-to-use-a-proxy-ubuntu/
Open the following configuration file: /etc/apt/apt.conf.d/70debconf
And add:
Acquire::http::proxy “http://<IP_TO_PROXY>:<Proxy_Port_WEB>”;
Acquire::ftp::proxy “ftp://<IP_TO_PROXY>:<Proxy_Port_FTP>”;
If authentication is required, add this instead
Acquire::http::proxy “http://<username>:<password>@<IP_TO_PROXY>:<Proxy_Port_WEB>”;
Acquire::ftp::proxy “ftp://<username>:<password>@<IP_TO_PROXY>:<Proxy_Port_FTP>”;
<IP_TO_PROXY> = The IP address of the proxy, e.g.: 192.168.1.10
<Proxy_Port_WEB> = The proxy web port, e.g.: 8080
<Proxy_Port_FTP> = The proxy ftp port, e.g.: 2121
If authentication:
<username> and <password> (doh, no need to explain).
Done!
Configure apt-get to use a proxy (Ubuntu)
原文：http://www.cnblogs.com/steadfast/p/4168675.html