ubuntu的源
deb http://mirrors.sohu.com/ubuntu/ natty main restricted universe multiverse
deb http://mirrors.sohu.com/ubuntu/ natty-security main restricted universe multiverse
deb http://mirrors.sohu.com/ubuntu/ natty-updates main restricted universe multiverse
deb http://mirrors.sohu.com/ubuntu/ natty-proposed main restricted universe multiverse
deb http://mirrors.sohu.com/ubuntu/ natty-backports main restricted universe multiverse
deb-src http://mirrors.sohu.com/ubuntu/ natty main restricted universe multiverse
deb-src http://mirrors.sohu.com/ubuntu/ natty-security main restricted universe multiverse
deb-src http://mirrors.sohu.com/ubuntu/ natty-updates main restricted universe multiverse
deb-src http://mirrors.sohu.com/ubuntu/ natty-proposed main restricted universe multiverse
deb-src http://mirrors.sohu.com/ubuntu/ natty-backports main restricted universe multiverse