If you have an $http_proxy at your site, where is the proper place to set it, so that things like 'sudo apt-get update' work properly?
Check if it works
First, to test that it's working properly for you, do:
sudo sh -c 'echo http_proxy: $http_proxy'
Make it work
Put this in your /etc/sudoers file (via visudo):
Defaults env_keep += "ftp_proxy http_proxy https_proxy no_proxy"
Maybe that seems strange/insecure? It's widely recommended though: