懒得搜索的，下面有一份源列表，建议复制一部分使用
# Archive.Ubuntu.com 更新服务器（欧洲，此为官方源）
deb feisty main restricted universe multiverse
deb feisty-security main restricted universe multiverse
deb feisty-updates main restricted universe multiverse
deb feisty-proposed main restricted universe multiverse
deb feisty-backports main restricted universe multiverse
deb-src feisty main restricted universe multiverse
deb-src feisty-security main restricted universe multiverse
deb-src feisty-updates main restricted universe multiverse
deb-src feisty-proposed main restricted universe multiverse
deb-src feisty-backports main restricted universe multiverse
# Ubuntu.cn99.com 更新服务器（江苏省常州市电信，推荐电信用户使用。）
deb feisty main restricted universe multiverse
deb feisty-security main restricted universe multiverse
deb feisty-updates main restricted universe multiverse
deb feisty-proposed main restricted universe multiverse
deb feisty-backports main restricted universe multiverse
deb-src feisty main restricted universe multiverse
deb-src feisty-security main restricted universe multiverse
deb-src feisty-updates main restricted universe multiverse
deb-src feisty-proposed main restricted universe multiverse
deb-src feisty-backports main restricted universe multiverse
deb feisty main restricted universe multiverse
# mirror.rootguide.org更新服务器 (上海市 电信):
deb feisty main restricted universe multiverse
deb-src feisty main restricted universe multiverse
deb feisty-updates main restricted universe multiverse
deb-src feisty-updates main restricted universe multiverse
deb feisty-backports main restricted universe multiverse
deb-src feisty-backports main restricted universe multiverse
deb feisty-security main restricted universe multiverse
deb-src feisty-security main restricted universe multiverse
deb feisty-proposed main multiverse restricted universe
deb-src feisty-proposed main restricted universe multiverse
deb feisty main multiverse restricted universe
# 台湾大学更新服务器（推荐网通用户使用，此源比较完整，较少出现同步问题)
deb feisty main restricted universe multiverse
deb-src feisty main restricted universe multiverse
deb feisty-updates main restricted universe multiverse
deb-src feisty-updates main restricted universe multiverse
deb feisty-backports main restricted universe multiverse
deb-src feisty-backports main restricted universe multiverse
deb feisty-security main restricted universe multiverse
deb-src feisty-security main restricted universe multiverse
deb feisty-proposed main multiverse restricted universe
deb-src feisty-proposed main restricted universe multiverse
# Mirror.lupaworld.com 更新服务器（浙江省杭州市电信，亚洲地区官方更新服务器）
deb feisty main restricted universe multiverse
deb feisty-security main restricted universe multiverse
deb feisty-updates main restricted universe multiverse
deb feisty-backports main restricted universe multiverse
deb feisty-proposed main restricted universe multiverse
deb-src feisty main restricted universe multiverse
deb-src feisty-security main restricted universe multiverse
deb-src feisty-updates main restricted universe multiverse
deb-src feisty-backports main restricted universe multiverse
deb-src feisty-proposed main restricted universe multiverse
deb feisty main restricted universe multiverse
# ubuntu.cnsite.org 更新服务器（福建省福州市 电信）
deb feisty main restricted universe multiverse
deb-src feisty main restricted universe multiverse
deb feisty-updates main restricted universe multiverse
deb-src feisty-updates main restricted universe multiverse
deb feisty-backports main restricted universe multiverse
deb-src feisty-backports main restricted universe multiverse
deb feisty-security main restricted universe multiverse
deb-src feisty-security main restricted universe multiverse
deb feisty-proposed main multiverse restricted universe
deb-src feisty-proposed main restricted universe multiverse
deb feisty main multiverse restricted universe
# 北 市清华大学 更新服务器（教育网，推荐校园网和网通用户使用）
deb feisty main multiverse restricted universe
deb feisty-backports main multiverse restricted universe
deb feisty-proposed main multiverse restricted universe
deb feisty-security main multiverse restricted universe
deb feisty-updates main multiverse restricted universe
deb-src feisty main multiverse restricted universe
deb-src feisty-backports main multiverse restricted universe
deb-src feisty-proposed main multiverse restricted universe
deb-src feisty-security main multiverse restricted universe
deb-src feisty-updates main multiverse restricted universe
deb feisty main multiverse restricted universe
将里面乱七八糟的东西删了，将你复制的源列表粘贴到里面，保存退出。