If you use Debian distribution-based and you connected to internet through proxy server, you will find some difficulties to manage your software in command line interface. Recently, I found the configuration that will tell APT (Advance Package Management) to use proxy. You just need to edit apt.conf file located in /etc/apt/apt.conf and add this lines:
Acquire{
http {
Proxy “http://username:password@yourproxyserveraddress:yourproxyserverport”;
Proxy::some.host.com “DIRECT”;
};
};
Hope that will help 
