Ubuntu中文版默认选择的是cn.archive.ubuntu.com作为更新源(如果喜欢英文界面的用户那么更新源默认是Ubuntu官网的)，在更新系统或者apt-get安装一些软件的时候速度会非常慢，大陆用户最好是添加其他合适的源到源列表的前面。我觉得速度比较不错的源是搜狐、网易和台湾的源，教育网的推荐使用北理工的，貌似这个学校是教育网的骨干节点。
不过很奇怪的是，中国ubuntu官方源(cn.archive.ubuntu.com)是搜狐维护的，和搜狐的镜像mirrors.sohu.com是同一个，但是搜狐却把这个源放在了山东网通这个二线机房，再加上具有中国特色的南北电信差异，直接导致很多南方用户使用中国ubuntu官方源的时候也很慢。我刚到搜狐一周，使用搜狐的源更新飞快，所以很奇怪为啥搜狐没有把这个源放在中心机房。
中国科学技术大学更新服务器（位于合肥，千兆教育网接入，百兆电信/联通线路智能路由），由中科大Linux 用户协会和中科大学网络信息中心维护，包含其他开源镜像，Deepin 官方服务器 实际亦指向此处：
deb http://debian.ustc.edu.cn/ubuntu/ trusty main multiverse restricted universe
deb http://debian.ustc.edu.cn/ubuntu/ trusty-backports main multiverse restricted universe
deb http://debian.ustc.edu.cn/ubuntu/ trusty-proposed main multiverse restricted universe
deb http://debian.ustc.edu.cn/ubuntu/ trusty-security main multiverse restricted universe
deb http://debian.ustc.edu.cn/ubuntu/ trusty-updates main multiverse restricted universe
deb-src http://debian.ustc.edu.cn/ubuntu/ trusty main multiverse restricted universe
deb-src http://debian.ustc.edu.cn/ubuntu/ trusty-backports main multiverse restricted universe
deb-src http://debian.ustc.edu.cn/ubuntu/ trusty-proposed main multiverse restricted universe
deb-src http://debian.ustc.edu.cn/ubuntu/ trusty-security main multiverse restricted universe
deb-src http://debian.ustc.edu.cn/ubuntu/ trusty-updates main multiverse restricted universe
首先使用apt-get update更新时候提示：
W: http://archive.:1 ... trusty/Release.gpg: 密钥 6CE35A4EBAB676094476BE7CD259B7555E1D3C58 生成的数字签名使用了弱安全性摘要算法(SHA1)
E: 无法下载 http://archive.:1 ... i18n/Translation-en 404 Not Found
E: 部分索引文件下载失败。如果忽略它们，那将转而使用旧的索引文件。
后面在ubuntukylin.list中把trusty改为了xenial
直接提示：
W: GPG 错误：http://archive.:10006/ubuntukylin xenial InRelease: 由于没有公钥，无法验证下列签名： NO_PUBKEY 8D5A09DC9B929006
W: 仓库 “http://archive.:10006/ubuntukylin xenial InRelease” 没有数字签名。
N: 无法认证来自该源的数据，所以使用它会带来潜在风险。
N: 参见 apt-secure(8) 手册以了解仓库创建和用户配置方面的细节。
W: 以下 ID 的密钥没有可用的公钥：
8D5A09DC9B929006
解决方法也很简单，缺少一个key的话，导入它就好了。
sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 8D5A09DC9B929006
##搜狐源(山东网通：适合网通用户)
deb http://mirrors.sohu.com/ubuntu/ precise main restricted universe multiverse
deb http://mirrors.sohu.com/ubuntu/ precise-security main restricted universe multiverse
deb http://mirrors.sohu.com/ubuntu/ precise-updates main restricted universe multiverse
deb http://mirrors.sohu.com/ubuntu/ precise-proposed main restricted universe multiverse
deb http://mirrors.sohu.com/ubuntu/ precise-backports main restricted universe multiverse
deb-src http://mirrors.sohu.com/ubuntu/ precise main restricted universe multiverse
deb-src http://mirrors.sohu.com/ubuntu/ precise-security main restricted universe multiverse
deb-src http://mirrors.sohu.com/ubuntu/ precise-updates main restricted universe multiverse
deb-src http://mirrors.sohu.com/ubuntu/ precise-proposed main restricted universe multiverse
deb-src http://mirrors.sohu.com/ubuntu/ precise-backports main restricted universe multiverse
##台湾ubuntu官网源
deb http://tw.archive.ubuntu.com/ubuntu precise main restricted universe multiverse
deb http://tw.archive.ubuntu.com/ubuntu precise-security main restricted universe multiverse
deb http://tw.archive.ubuntu.com/ubuntu precise-updates main restricted universe multiverse
deb http://tw.archive.ubuntu.com/ubuntu precise-backports main restricted universe multiverse
deb http://tw.archive.ubuntu.com/ubuntu precise-proposed main restricted universe multiverse
deb-src http://tw.archive.ubuntu.com/ubuntu precise main restricted universe multiverse
deb-src http://tw.archive.ubuntu.com/ubuntu precise-security main restricted universe multiverse
deb-src http://tw.archive.ubuntu.com/ubuntu precise-updates main restricted universe multiverse
deb-src http://tw.archive.ubuntu.com/ubuntu precise-backports main restricted universe multiverse
deb-src http://tw.archive.ubuntu.com/ubuntu precise-proposed main restricted universe multiverse
##教育网帝都的可以使用北理工的源
deb http://mirror.bit.edu.cn/ubuntu/ precise main restricted universe multiverse
deb http://mirror.bit.edu.cn/ubuntu/ precise-security main restricted universe multiverse
deb http://mirror.bit.edu.cn/ubuntu/ precise-updates main restricted universe multiverse
deb http://mirror.bit.edu.cn/ubuntu/ precise-backports main restricted universe multiverse
deb http://mirror.bit.edu.cn/ubuntu/ precise-proposed main restricted universe multiverse
deb-src http://mirror.bit.edu.cn/ubuntu/ precise main restricted universe multiverse
deb-src http://mirror.bit.edu.cn/ubuntu/ precise-security main restricted universe multiverse
deb-src http://mirror.bit.edu.cn/ubuntu/ precise-updates main restricted universe multiverse
deb-src http://mirror.bit.edu.cn/ubuntu/ precise-backports main restricted universe multiverse
deb-src http://mirror.bit.edu.cn/ubuntu/ precise-proposed main restricted universe multiverse
##网易源(广东电信：适合电信用户)
deb http://mirrors.163.com/ubuntu/ precise main restricted universe multiverse
deb http://mirrors.163.com/ubuntu/ precise-security main restricted universe multiverse
deb http://mirrors.163.com/ubuntu/ precise-updates main restricted universe multiverse
deb http://mirrors.163.com/ubuntu/ precise-proposed main restricted universe multiverse
deb http://mirrors.163.com/ubuntu/ precise-backports main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ precise main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ precise-security main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ precise-updates main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ precise-proposed main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ precise-backports main restricted universe multiverse
更改过/etc/apt/sources.list之后一定要执行apt-get update进行更新，其他linux发行版本一般都可以在上述镜像找到各自的更新源。
不同的网络状况连接以下源的速度不同, 建议在添加前手动验证以下源的连接速度(ping下就行),选择最快的源可以节省大批下载时间。
sudo cp /etc/apt/sources.list /etc/apt/sources.list_backup
sudo gedit /etc/apt/sources.list
sudo kate /etc/apt/sources.list
sudo mousepad /etc/apt/sources.list
sudo leafpad /etc/apt/sources.list (13.04版)
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