If you are a Debian-based GNU/Linux user, then you’re probably familiar with synaptic and apt-get to install application from software repositories. This post focussed on how to use apt-get/synaptic behind proxy server/firewall which under normal circumstances, you’re unable to use apt-get.
If you’re using Synaptic
Open up your Synaptic package manager (usually as root), go to Settings-> Preference -> Network. Enter your proxy server details like : username:email@example.com, and put the proxy server port (usually 8080).
If you’re using command-line apt-get
Edit your /etc/bash.bashrc file as root.
>sudo gedit /etc/bash.bashrc
Put these line at the end of your /etc/bash.bashrc file :
You can omit the username:password, if your proxy server has no password.
debian,ubuntu,knoppix, mepis, apt-get
How to use apt-get behind proxy server (Ubuntu/Debian)