Ubuntu proxy settings
For apt, software center etc
edit file /etc/apt/apt.conf
Acquire::http::proxy "http://username:password@host:port/";
Acquire::ftp::proxy "ftp://username:password@host:port/";
Acquire::https::proxy "https://username:password@host:port/";
Environment variables
edit file /etc/environment
http_proxy=http://username:password@host:port/
ftp_proxy=ftp://username:password@host:port/
https_proxy=https://username:password@host:port/
Source: https://askubuntu.com/questions/664777/systemwide-proxy-settings-in-ubuntu
Written on April 19, 2017