Linux - Configurando proxy do ambiente

proxy.txt

export http_proxy=http://user:password@proxy:port/
export https_proxy=http://user:password@proxy:port/
export ftp_proxy=http://user:password@proxy:port/

export no_proxy=localhost

Se o apt-get não funcionar, adicionar as linhas abaixo no arquivo /etc/apt/apt.conf

Acquire::http::proxy "http://user:password@proxy:port/";
Acquire::https::proxy "http://user:password@proxy:port/";
Acquire::ftp::proxy "http://user:password@proxy:port/";
Acquire::socks::proxy "http://user:password@proxy:port/";