Ubuntu 13.04 无法apt-get update 的解决办法

refer to: http://tieba.baidu.com/p/3185606743

13.04已经停止更新，所以已经从源中移除了，当然找不到文件。

假如你不升级，就是只要用13.04
把所有 http://cn.archive.ubuntu.com/ubuntu/
改成 http://old-releases.ubuntu.com/ubuntu/

办法2： 升级到 13.10 ( refer to: http://askubuntu.com/questions/455741/upgrade-from-13-04-to-14-04)

Not an official tutorial, but worked successfully for me with lubuntu.

1. Change /etc/apt/sources.list to a 13.10 repository
(use the list generator from http://repogen.simplylinux.ch/)

# http://wiki.ubuntu.org.cn/Template:13.10source
deb http://mirrors.sohu.com/ubuntu/ saucy main restricted universe multiverse
deb http://mirrors.sohu.com/ubuntu/ saucy-security main restricted universe multiverse
deb http://mirrors.sohu.com/ubuntu/ saucy-updates main restricted universe multiverse
deb http://mirrors.sohu.com/ubuntu/ saucy-proposed main restricted universe multiverse
deb http://mirrors.sohu.com/ubuntu/ saucy-backports main restricted universe multiverse
deb-src http://mirrors.sohu.com/ubuntu/ saucy main restricted universe multiverse
deb-src http://mirrors.sohu.com/ubuntu/ saucy-security main restricted universe multiverse
deb-src http://mirrors.sohu.com/ubuntu/ saucy-updates main restricted universe multiverse
deb-src http://mirrors.sohu.com/ubuntu/ saucy-proposed main restricted universe multiverse
deb-src http://mirrors.sohu.com/ubuntu/ saucy-backports main restricted universe multiverse

2. apt-get update && apt-get upgrade && reboot && apt-get dist-upgrade
(will upgrade to 13.10. Don't panik if your desktop is lost. Solve this by clearing desktop configs in your /home/userxxx and re-login)

3. reboot (just in case)

4. start the software updater and run the 14.04 LTS upgrade

5. Your're done.

May take quite a bit of time (2 dist upgrades) and is not guaranteed to
work in every situation, but if not, re-installing is still an option.