来自： http://blog.csdn.net/xgbing/article/details/50573016

    换了网上几个软件源后均不能用，提示HASH错误，偶尔找到一篇文章讲到可以使用ftp，我改了一下竟然可以用了:

# deb cdrom:[Xubuntu 12.04.4 LTS _Precise Pangolin_ - Release amd64 (20140205)]/ dists/precise/main/binary-i386/

# deb cdrom:[Xubuntu 12.04.4 LTS _Precise Pangolin_ - Release amd64 (20140205)]/ dists/precise/multiverse/binary-i386/
# deb cdrom:[Xubuntu 12.04.4 LTS _Precise Pangolin_ - Release amd64 (20140205)]/ dists/precise/restricted/binary-i386/
# deb cdrom:[Xubuntu 12.04.4 LTS _Precise Pangolin_ - Release amd64 (20140205)]/ dists/precise/universe/binary-i386/
# deb cdrom:[Xubuntu 12.04.4 LTS _Precise Pangolin_ - Release amd64 (20140205)]/ precise main multiverse restricted universe

# See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
# newer versions of the distribution.
deb ftp://mirrors.ustc.edu.cn/ubuntu/ precise main restricted
deb-src ftp://mirrors.ustc.edu.cn/ubuntu/ precise main restricted

## Major bug fix updates produced after the final release of the
## distribution.
deb ftp://mirrors.ustc.edu.cn/ubuntu/ precise-updates main restricted
deb-src ftp://mirrors.ustc.edu.cn/ubuntu/ precise-updates main restricted

## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team. Also, please note that software in universe WILL NOT receive any
## review or updates from the Ubuntu security team.
deb ftp://mirrors.ustc.edu.cn/ubuntu/ precise universe
deb-src http://mirrors.ustc.edu.cn/ubuntu/ precise universe
deb ftp://mirrors.ustc.edu.cn/ubuntu/ precise-updates universe
deb-src ftp://mirrors.ustc.edu.cn/ubuntu/ precise-updates universe

## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team, and may not be under a free licence. Please satisfy yourself as to
## your rights to use the software. Also, please note that software in
## multiverse WILL NOT receive any review or updates from the Ubuntu
## security team.
deb ftp://mirrors.ustc.edu.cn/ubuntu/ precise multiverse
deb-src ftp://mirrors.ustc.edu.cn/ubuntu/ precise multiverse
deb ftp://mirrors.ustc.edu.cn/ubuntu/ precise-updates multiverse
deb-src ftp://mirrors.ustc.edu.cn/ubuntu/ precise-updates multiverse

## N.B. software from this repository may not have been tested as
## extensively as that contained in the main release, although it includes
## newer versions of some applications which may provide useful features.
## Also, please note that software in backports WILL NOT receive any review
## or updates from the Ubuntu security team.
deb ftp://mirrors.ustc.edu.cn/ubuntu/ precise-backports main restricted universe multiverse
deb-src ftp://mirrors.ustc.edu.cn/ubuntu/ precise-backports main restricted universe multiverse

deb ftp://security.mirrors.ustc.edu.cn/ubuntu precise-security main restricted
deb-src ftp://security.mirrors.ustc.edu.cn/ubuntu precise-security main restricted
deb ftp://security.mirrors.ustc.edu.cn/ubuntu precise-security universe
deb-src ftp://security.mirrors.ustc.edu.cn/ubuntu precise-security universe
deb ftp://security.mirrors.ustc.edu.cn/ubuntu precise-security multiverse
deb-src ftp://security.mirrors.ustc.edu.cn/ubuntu precise-security multiverse

## Uncomment the following two lines to add software from Canonical's
## 'partner' repository.
## This software is not part of Ubuntu, but is offered by Canonical and the
## respective vendors as a service to Ubuntu users.
# deb http://archive.canonical.com/ubuntu precise partner
# deb-src http://archive.canonical.com/ubuntu precise partner

## This software is not part of Ubuntu, but is offered by third-party
## developers who want to ship their latest software.
# deb http://extras.ubuntu.com/ubuntu precise main
# deb-src http://extras.ubuntu.com/ubuntu precise main