Using Ubuntu Package Manager (apt-get) without direct web access

Need to install an Ubuntu package on a system that is not directly connected to the Internet? Well, if you have a HTTP proxy nearby, you can do it as follows:

# cd /etc/apt/apt.conf.d
# vi proxy
Acquire::http::Proxy "http://x.x.x.x:80";

Just edit/create the file above and add the line shown (substituting the IP address or hostname of your proxy server) and use your apt-get command(s) as normal. No need to restart any processed.