ubuntu 无法找到软件包

增加 源

打开控制台，输入命令：
sudo gedit /etc/apt/sources.list

然后在最后添加以下源：
deb http://ubuntu.cn99.com/ubuntu/ gutsy main restricted universe multiverse
deb http://ubuntu.cn99.com/ubuntu/ gutsy-security main restricted universe multiverse
deb http://ubuntu.cn99.com/ubuntu/ gutsy-updates main restricted universe multiverse
deb http://ubuntu.cn99.com/ubuntu/ gutsy-proposed main restricted universe multiverse
deb http://ubuntu.cn99.com/ubuntu/ gutsy-backports main restricted universe multiverse
deb-src http://ubuntu.cn99.com/ubuntu/ gutsy main restricted universe multiverse
deb-src http://ubuntu.cn99.com/ubuntu/ gutsy-security main restricted universe multiverse
deb-src http://ubuntu.cn99.com/ubuntu/ gutsy-updates main restricted universe multiverse
deb-src http://ubuntu.cn99.com/ubuntu/ gutsy-proposed main restricted universe multiverse
deb-src http://ubuntu.cn99.com/ubuntu/ gutsy-backports main restricted universe multiverse
deb http://ubuntu.cn99.com/ubuntu/ edgy main restricted universe multiverse
deb http://ubuntu.cn99.com/ubuntu/ edgy-security main restricted universe multiverse
deb http://ubuntu.cn99.com/ubuntu/ edgy-updates main restricted universe multiverse
deb http://ubuntu.cn99.com/ubuntu/ edgy-proposed main restricted universe multiverse
deb http://ubuntu.cn99.com/ubuntu/ edgy-backports main restricted universe multiverse
deb-src http://ubuntu.cn99.com/ubuntu/ edgy main restricted universe multiverse
deb-src http://ubuntu.cn99.com/ubuntu/ edgy-security main restricted universe multiverse
deb-src http://ubuntu.cn99.com/ubuntu/ edgy-updates main restricted universe multiverse
deb-src http://ubuntu.cn99.com/ubuntu/ edgy-proposed main restricted universe multiverse
deb-src http://ubuntu.cn99.com/ubuntu/ edgy-backports main restricted universe multiverse
deb http://ubuntu.cn99.com/ubuntu-cn/ edgy main restricted universe multiverse

#传说中的中国科技大学 5M/s
 deb http://debian.ustc.edu.cn/ubuntu/ feisty main restricted universe multiverse
 deb http://debian.ustc.edu.cn/ubuntu/ feisty-backports restricted universe multiverse
 deb http://debian.ustc.edu.cn/ubuntu/ feisty-proposed main restricted universe multiverse
 deb http://debian.ustc.edu.cn/ubuntu/ feisty-security main restricted universe multiverse
 deb http://debian.ustc.edu.cn/ubuntu/ feisty-updates main restricted universe multiverse
 deb-src http://debian.ustc.edu.cn/ubuntu/ feisty main restricted universe multiverse
 deb-src http://debian.ustc.edu.cn/ubuntu/ feisty-backports main restricted universe multiverse
 deb-src http://debian.ustc.edu.cn/ubuntu/ feisty-proposed main restricted universe multiverse
 deb-src http://debian.ustc.edu.cn/ubuntu/ feisty-security main restricted universe multiverse
 deb-src http://debian.ustc.edu.cn/ubuntu/ feisty-updates main restricted universe multiverse
#传说中的北京交大 速度 2M/s
 deb http://mirror.bjtu.edu.cn/ubuntu/ feisty main restricted universe multiverse
 deb http://mirror.bjtu.edu.cn/ubuntu/ feisty-updates main restricted universe multiverse
 deb http://mirror.bjtu.edu.cn/ubuntu/ feisty-security main restricted universe multiverse
 deb http://mirror.bjtu.edu.cn/ubuntu/ feisty-backports main restricted universe multiverse
#传说中的上海交通大学，听说现在硬盘挂了，500k/s 曾经最热门的源之一
 deb http://ftp.sjtu.edu.cn/ubuntu/ feisty main multiverse restricted universe
 deb http://ftp.sjtu.edu.cn/ubuntu/ feisty-backports main multiverse restricted universe
 deb http://ftp.sjtu.edu.cn/ubuntu/ feisty-proposed main multiverse restricted universe
 deb http://ftp.sjtu.edu.cn/ubuntu/ feisty-security main multiverse restricted universe
 deb http://ftp.sjtu.edu.cn/ubuntu/ feisty-updates main multiverse restricted universe
 deb http://ftp.sjtu.edu.cn/ubuntu-cn/ feisty main multiverse restricted universe
 deb-src http://ftp.sjtu.edu.cn/ubuntu/ feisty main multiverse restricted universe
 deb-src http://ftp.sjtu.edu.cn/ubuntu/ feisty-backports main multiverse restricted universe
 deb-src http://ftp.sjtu.edu.cn/ubuntu/ feisty-proposed main multiverse restricted universe
 deb-src http://ftp.sjtu.edu.cn/ubuntu/ feisty-security main multiverse restricted universe
 deb-src http://ftp.sjtu.edu.cn/ubuntu/ feisty-updates main multiverse restricted universe
#真正可以上的清华大学ubuntu源 300k/s
 deb ftp://ftp3.tsinghua.edu.cn/mirror/ubuntu/ubuntu/ feisty main restricted universe multiverse
 deb ftp://ftp3.tsinghua.edu.cn/mirror/ubuntu/ubuntu/ feisty-security main restricted universe multiverse
 deb ftp://ftp3.tsinghua.edu.cn/mirror/ubuntu/ubuntu/ feisty-updates main restricted universe multiverse
#传说中的兰州大学 260k/s
 deb ftp://mirror.lzu.edu.cn/ubuntu/ feisty main multiverse restricted universe
 deb ftp://mirror.lzu.edu.cn/ubuntu/ feisty-backports main multiverse restricted universe
 deb ftp://mirror.lzu.edu.cn/ubuntu/ feisty-proposed main multiverse restricted universe
 deb ftp://mirror.lzu.edu.cn/ubuntu/ feisty-security main multiverse restricted universe
 deb ftp://mirror.lzu.edu.cn/ubuntu/ feisty-updates main multiverse restricted universe
 deb ftp://mirror.lzu.edu.cn/ubuntu-cn/ feisty main multiverse restricted universe
#传说中的台湾大学 中国电信adsl 150k/s
 deb http://ubuntu.csie.ntu.edu.tw/ubuntu/ feisty main restricted universe multiverse
 deb-src http://ubuntu.csie.ntu.edu.tw/ubuntu/ feisty main restricted universe multiverse
 deb http://ubuntu.csie.ntu.edu.tw/ubuntu/ feisty-updates main restricted universe multiverse
 deb-src http://ubuntu.csie.ntu.edu.tw/ubuntu/ feisty-updates main restricted universe multiverse
 deb http://ubuntu.csie.ntu.edu.tw/ubuntu/ feisty-backports main restricted universe multiverse
 deb-src http://ubuntu.csie.ntu.edu.tw/ubuntu/ feisty-backports main restricted universe multiverse
 deb http://ubuntu.csie.ntu.edu.tw/ubuntu/ feisty-security main restricted universe multiverse
 deb-src http://ubuntu.csie.ntu.edu.tw/ubuntu/ feisty-security main restricted universe multiverse
以下为 ubuntu edgy 6.10
#传说中的中国科技大学 速度： 5M/s
 deb ftp://debian.ustc.edu.cn/ubuntu edgy main restricted universe multiverse
 deb ftp://debian.ustc.edu.cn/ubuntu edgy-security main restricted universe multiverse
 deb ftp://debian.ustc.edu.cn/ubuntu edgy-updates main restricted universe multiverse
 deb ftp://debian.ustc.edu.cn/ubuntu edgy-backports main restricted universe multiverse
 deb ftp://debian.ustc.edu.cn/ubuntu edgy-proposed main restricted universe multiverse
#传说中的北京交大 速度 2M/s
 deb http://mirror.bjtu.edu.cn/ubuntu/ edgy main restricted universe multiverse
 deb http://mirror.bjtu.edu.cn/ubuntu/ edgy-updates main restricted universe multiverse
 deb http://mirror.bjtu.edu.cn/ubuntu/ edgy-security main restricted universe multiverse
 deb http://mirror.bjtu.edu.cn/ubuntu/ edgy-backports main restricted universe multiverse
#试试这个清华的源
 deb http://mirror9.net9.org/ubuntu/ edgy main multiverse restricted universe
 deb http://mirror9.net9.org/ubuntu/ edgy-backports main multiverse restricted universe
 deb http://mirror9.net9.org/ubuntu/ edgy-proposed main multiverse restricted universe
 deb http://mirror9.net9.org/ubuntu/ edgy-security main multiverse restricted universe
 deb http://mirror9.net9.org/ubuntu/ edgy-updates main multiverse restricted universe
 deb-src http://mirror9.net9.org/ubuntu/ edgy main multiverse restricted universe
 deb-src http://mirror9.net9.org/ubuntu/ edgy-backports main multiverse restricted universe
 deb-src http://mirror9.net9.org/ubuntu/ edgy-proposed main multiverse restricted universe
 deb-src http://mirror9.net9.org/ubuntu/ edgy-security main multiverse restricted universe
 deb-src http://mirror9.net9.org/ubuntu/ edgy-updates main multiverse restricted universe
 deb http://mirror9.net9.org/ubuntu-cn/ edgy main multiverse restricted universe
#真正可以上的清华大学ubuntu源
 deb ftp://ftp3.tsinghua.edu.cn/mirror/ubuntu/ubuntu/ edgy main restricted universe multiverse
 deb ftp://ftp3.tsinghua.edu.cn/mirror/ubuntu/ubuntu/ edgy-security main restricted universe multiverse
 deb ftp://ftp3.tsinghua.edu.cn/mirror/ubuntu/ubuntu/ edgy-updates main restricted universe multiverse
#传说中的上海交通大学，听说现在硬盘挂了，曾经最热门的源之一
 deb http://ftp.sjtu.edu.cn/ubuntu/ edgy main multiverse restricted universe
 deb http://ftp.sjtu.edu.cn/ubuntu/ edgy-backports main multiverse restricted universe
 deb http://ftp.sjtu.edu.cn/ubuntu/ edgy-proposed main multiverse restricted universe
 deb http://ftp.sjtu.edu.cn/ubuntu/ edgy-security main multiverse restricted universe
 deb http://ftp.sjtu.edu.cn/ubuntu/ edgy-updates main multiverse restricted universe
 deb-src http://ftp.sjtu.edu.cn/ubuntu/ edgy main multiverse restricted universe
 deb-src http://ftp.sjtu.edu.cn/ubuntu/ edgy-backports main multiverse restricted universe
 deb-src http://ftp.sjtu.edu.cn/ubuntu/ edgy-proposed main multiverse restricted universe
 deb-src http://ftp.sjtu.edu.cn/ubuntu/ edgy-security main multiverse restricted universe
 deb-src http://ftp.sjtu.edu.cn/ubuntu/ edgy-updates main multiverse restricted universe
 deb http://ftp.sjtu.edu.cn/ubuntu-cn/ edgy main multiverse restricted universe
##传说中的兰州大学
 deb ftp://mirror.lzu.edu.cn/ubuntu/ edgy main multiverse restricted universe
 deb ftp://mirror.lzu.edu.cn/ubuntu/ edgy-backports main multiverse restricted universe
 deb ftp://mirror.lzu.edu.cn/ubuntu/ edgy-proposed main multiverse restricted universe
 deb ftp://mirror.lzu.edu.cn/ubuntu/ edgy-security main multiverse restricted universe
 deb ftp://mirror.lzu.edu.cn/ubuntu/ edgy-updates main multiverse restricted universe
 deb ftp://mirror.lzu.edu.cn/ubuntu-cn/ edgy main multiverse restricted universe
#传说中的台湾大学 中国电信adsl 150k/s
 deb http://ubuntu.csie.ntu.edu.tw/ubuntu/ edgy main restricted universe multiverse
 deb-src http://ubuntu.csie.ntu.edu.tw/ubuntu/ edgy main restricted universe multiverse
 deb http://ubuntu.csie.ntu.edu.tw/ubuntu/ edgy-updates main restricted universe multiverse
 deb-src http://ubuntu.csie.ntu.edu.tw/ubuntu/ edgy-updates main restricted universe multiverse
 deb http://ubuntu.csie.ntu.edu.tw/ubuntu/ edgy-backports main restricted universe multiverse
 deb-src http://ubuntu.csie.ntu.edu.tw/ubuntu/ edgy-backports main restricted universe multiverse
 deb http://ubuntu.csie.ntu.edu.tw/ubuntu/ edgy-security main restricted universe multiverse
 deb-src http://ubuntu.csie.ntu.edu.tw/ubuntu/ edgy-security main restricted universe multiverse

 #以下为ubuntu dapper 6.06

 #传说中的中国科技大学
 deb ftp://debian.ustc.edu.cn/ubuntu dapper main restricted universe multiverse
 deb ftp://debian.ustc.edu.cn/ubuntu dapper-security main restricted universe multiverse
 deb ftp://debian.ustc.edu.cn/ubuntu dapper-updates main restricted universe multiverse
 deb ftp://debian.ustc.edu.cn/ubuntu dapper-backports main restricted universe multiverse
 deb ftp://debian.ustc.edu.cn/ubuntu dapper-proposed main restricted universe multiverse
#传说中的北京交通大学
 deb http://mirror.bjtu.edu.cn/ubuntu/ dapper main restricted universe multiverse
 deb http://mirror.bjtu.edu.cn/ubuntu/ dapper-updates main restricted universe multiverse
 deb http://mirror.bjtu.edu.cn/ubuntu/ dapper-security main restricted universe multiverse
 deb http://mirror.bjtu.edu.cn/ubuntu/ dapper-backports main restricted universe multiverse
#真正能用的清华大学的源
 deb ftp://ftp3.tsinghua.edu.cn/mirror/ubuntu/ubuntu/ dapper main restricted universe multiverse
 deb ftp://ftp3.tsinghua.edu.cn/mirror/ubuntu/ubuntu/ dapper-security main restricted universe multiverse
 deb ftp://ftp3.tsinghua.edu.cn/mirror/ubuntu/ubuntu/ dapper-updates main restricted universe multiverse
#传说中的上海交通大学，听说现在硬盘挂了，曾经最热门的源之一
 deb http://ftp.sjtu.edu.cn/ubuntu/ dapper main multiverse restricted universe
 deb http://ftp.sjtu.edu.cn/ubuntu/ dapper-backports main multiverse restricted universe
 deb http://ftp.sjtu.edu.cn/ubuntu/ dapper-proposed main multiverse restricted universe
 deb http://ftp.sjtu.edu.cn/ubuntu/ dapper-security main multiverse restricted universe
 deb http://ftp.sjtu.edu.cn/ubuntu/ dapper-updates main multiverse restricted universe
 deb-src http://ftp.sjtu.edu.cn/ubuntu/ dapper main multiverse restricted universe
 deb-src http://ftp.sjtu.edu.cn/ubuntu/ dapper-backports main multiverse restricted universe
 deb-src http://ftp.sjtu.edu.cn/ubuntu/ dapper-proposed main multiverse restricted universe
 deb-src http://ftp.sjtu.edu.cn/ubuntu/ dapper-security main multiverse restricted universe
 deb-src http://ftp.sjtu.edu.cn/ubuntu/ dapper-updates main multiverse restricted universe
 deb http://ftp.sjtu.edu.cn/ubuntu-cn/ dapper main multiverse restricted universe
#传说中的兰州大学
 deb ftp://mirror.lzu.edu.cn/ubuntu/ dapper main multiverse restricted universe
 deb ftp://mirror.lzu.edu.cn/ubuntu/ dapper-backports main multiverse restricted universe
 deb ftp://mirror.lzu.edu.cn/ubuntu/ dapper-proposed main multiverse restricted universe
 deb ftp://mirror.lzu.edu.cn/ubuntu/ dapper-security main multiverse restricted universe
 deb ftp://mirror.lzu.edu.cn/ubuntu/ dapper-updates main multiverse restricted universe
 deb ftp://mirror.lzu.edu.cn/ubuntu-cn/ dapper main multiverse restricted universe
#传说中的台湾大学
 deb http://ubuntu.csie.ntu.edu.tw/ubuntu/ dapper main restricted universe multiverse
 deb-src http://ubuntu.csie.ntu.edu.tw/ubuntu/ dapper main restricted universe multiverse
 deb http://ubuntu.csie.ntu.edu.tw/ubuntu/ dapper-updates main restricted universe multiverse
 deb-src http://ubuntu.csie.ntu.edu.tw/ubuntu/ dapper-updates main restricted universe multiverse
 deb http://ubuntu.csie.ntu.edu.tw/ubuntu/ dapper-backports main restricted universe multiverse
 deb-src http://ubuntu.csie.ntu.edu.tw/ubuntu/ dapper-backports main restricted universe multiverse
 deb http://ubuntu.csie.ntu.edu.tw/ubuntu/ dapper-security main restricted universe multiverse
 deb-src http://ubuntu.csie.ntu.edu.tw/ubuntu/ dapper-security main restricted universe multiverse

保存，退出，再执行：
sudo apt-get update