例如：
HTTP(S) 代理服务器：127.0.0.1:54483
SOCKS 代理服务器：127.0.0.1:66161
用 sudo 修改 /etc/apt/apt.conf 文件：
zds@ubuntu:~$ sudo vim /etc/apt/apt.conf
zds@ubuntu:~$ nl /etc/apt/apt.conf
1 Acquire::http::proxy "http://127.0.0.1:54483/";
2 Acquire::https::proxy "https://127.0.0.1:54483/";
3 Acquire::ftp::proxy "ftp://127.0.0.1:54483/";
4 Acquire::socks::proxy "socks://127.0.0.1:66161";
