apt-get 使用代理进行update upgrade

apt-get有一个“-o”选项，直接设置apt-get的变量。比如

sudo apt-get -o Acquire::http::proxy="http://127.0.0.1:8000/" update
sudo apt-get -o Acquire::ftp::proxy="ftp://127.0.0.1:8000/" update
sudo apt-get -o Acquire::https::proxy="https://127.0.0.1:8000/" update