1. 修改us.archive.ubuntu.com为cn.archive.ubuntu.com
默认的，apt-get会连接http://us.archive.ubuntu.com/
这是一个美国的服务器。
可以通过/etc/apt/sources.list修改，
把其中的us.archive.ubuntu.com替换成cn.archive.ubuntu.com就可以使用中国的软件源了。
2.添加更新源
#sudo cp /etc/apt/sources.list /etc/apt/sources.list_bk
#sudo gedit /etc/apt/sources.list
deb http://mirrors.163.com/Ubuntu/ lucid main universe recript：ed multiverse
deb-src http://mirrors.163.com/Ubuntu/ lucid main universe recript：ed multiverse
deb http://mirrors.163.com/Ubuntu/ lucid-security universe main multiverse recript：ed
deb-src http://mirrors.163.com/Ubuntu/ lucid-security universe main multiverse recript：ed
deb http://mirrors.163.com/Ubuntu/ lucid-updates universe main multiverse recript：ed
deb http://mirrors.163.com/Ubuntu/ lucid-proposed universe main multiverse recript：ed
deb-src http://mirrors.163.com/Ubuntu/ lucid-proposed universe main multiverse recript：ed
deb http://mirrors.163.com/Ubuntu/ lucid-backports universe main multiverse recript：ed
deb-src http://mirrors.163.com/Ubuntu/ lucid-backports universe main multiverse recript：ed
deb-src http://mirrors.163.com/Ubuntu/ lucid-updates universe main multiverse recript：ed