修改方法：vim /etc/apt/sources.list，然后添加下面对应的代码区
中科大镜像源
deb https://mirrors.ustc.edu.cn/ubuntu/ bionic main restricted universe multiverse deb-src https://mirrors.ustc.edu.cn/ubuntu/ bionic main restricted universe multiverse deb https://mirrors.ustc.edu.cn/ubuntu/ bionic-updates main restricted universe multiverse deb-src https://mirrors.ustc.edu.cn/ubuntu/ bionic-updates main restricted universe multiverse deb https://mirrors.ustc.edu.cn/ubuntu/ bionic-backports main restricted universe multiverse deb-src https://mirrors.ustc.edu.cn/ubuntu/ bionic-backports main restricted universe multiverse deb https://mirrors.ustc.edu.cn/ubuntu/ bionic-security main restricted universe multiverse deb-src https://mirrors.ustc.edu.cn/ubuntu/ bionic-security main restricted universe multiverse deb https://mirrors.ustc.edu.cn/ubuntu/ bionic-proposed main restricted universe multiverse deb-src https://mirrors.ustc.edu.cn/ubuntu/ bionic-proposed main restricted universe multiverse
台湾的官方源
deb http://tw.archive.ubuntu.com/ubuntu karmic main restricted universe multiverse deb http://tw.archive.ubuntu.com/ubuntu karmic-security main restricted universe multiverse deb http://tw.archive.ubuntu.com/ubuntu karmic-updates main restricted universe multiverse deb http://tw.archive.ubuntu.com/ubuntu karmic-backports main restricted universe multiverse deb http://tw.archive.ubuntu.com/ubuntu karmic-proposed main restricted universe multiverse deb-src http://tw.archive.ubuntu.com/ubuntu karmic main restricted universe multiverse deb-src http://tw.archive.ubuntu.com/ubuntu karmic-security main restricted universe multiverse deb-src http://tw.archive.ubuntu.com/ubuntu karmic-updates main restricted universe multiverse deb-src http://tw.archive.ubuntu.com/ubuntu karmic-backports main restricted universe multiverse deb-src http://tw.archive.ubuntu.com/ubuntu karmic-proposed main restricted universe multiverse
中国台湾 台湾大学更新服务器
deb http://ubuntu.csie.ntu.edu.tw/ubuntu/ karmic main restricted universe multiverse deb-src http://ubuntu.csie.ntu.edu.tw/ubuntu/ karmic main restricted universe multiverse deb http://ubuntu.csie.ntu.edu.tw/ubuntu/ karmic-updates main restricted universe multiverse deb-src http://ubuntu.csie.ntu.edu.tw/ubuntu/ karmic-updates main restricted universe multiverse deb http://ubuntu.csie.ntu.edu.tw/ubuntu/ karmic-backports main restricted universe multiverse deb-src http://ubuntu.csie.ntu.edu.tw/ubuntu/ karmic-backports main restricted universe multiverse deb http://ubuntu.csie.ntu.edu.tw/ubuntu/ karmic-security main restricted universe multiverse deb-src http://ubuntu.csie.ntu.edu.tw/ubuntu/ karmic-security main restricted universe multiverse deb http://ubuntu.csie.ntu.edu.tw/ubuntu/ karmic-proposed main multiverse restricted universe deb-src http://ubuntu.csie.ntu.edu.tw/ubuntu/ karmic-proposed main restricted universe multiverse
网易163更新服务器：
deb http://mirrors.163.com/ubuntu/ karmic main restricted universe multiverse deb http://mirrors.163.com/ubuntu/ karmic-security main restricted universe multiverse deb http://mirrors.163.com/ubuntu/ karmic-updates main restricted universe multiverse deb http://mirrors.163.com/ubuntu/ karmic-proposed main restricted universe multiverse deb http://mirrors.163.com/ubuntu/ karmic-backports main restricted universe multiverse deb-src http://mirrors.163.com/ubuntu/ karmic main restricted universe multiverse deb-src http://mirrors.163.com/ubuntu/ karmic-security main restricted universe multiverse deb-src http://mirrors.163.com/ubuntu/ karmic-updates main restricted universe multiverse deb-src http://mirrors.163.com/ubuntu/ karmic-proposed main restricted universe multiverse deb-src http://mirrors.163.com/ubuntu/ karmic-backports main restricted universe multiverse
sohu 更新服务器：
deb http://mirrors.sohu.com/ubuntu/ karmic main restricted universe multiverse deb http://mirrors.sohu.com/ubuntu/ karmic-security main restricted universe multiverse deb http://mirrors.sohu.com/ubuntu/ karmic-updates main restricted universe multiverse deb http://mirrors.sohu.com/ubuntu/ karmic-proposed main restricted universe multiverse deb http://mirrors.sohu.com/ubuntu/ karmic-backports main restricted universe multiverse deb-src http://mirrors.sohu.com/ubuntu/ karmic main restricted universe multiverse deb-src http://mirrors.sohu.com/ubuntu/ karmic-security main restricted universe multiverse deb-src http://mirrors.sohu.com/ubuntu/ karmic-updates main restricted universe multiverse deb-src http://mirrors.sohu.com/ubuntu/ karmic-proposed main restricted universe multiverse deb-src http://mirrors.sohu.com/ubuntu/ karmic-backports main restricted universe multiverse
骨头兄亲自搭建并维护这个Ubuntu源
deb http://ubuntu.srt.cn/ubuntu/ karmic main restricted universe multiverse deb http://ubuntu.srt.cn/ubuntu/ karmic-security main restricted universe multiverse deb http://ubuntu.srt.cn/ubuntu/ karmic-updates main restricted universe multiverse deb http://ubuntu.srt.cn/ubuntu/ karmic-proposed main restricted universe multiverse deb http://ubuntu.srt.cn/ubuntu/ karmic-backports main restricted universe multiverse deb-src http://ubuntu.srt.cn/ubuntu/ karmic main restricted universe multiverse deb-src http://ubuntu.srt.cn/ubuntu/ karmic-security main restricted universe multiverse deb-src http://ubuntu.srt.cn/ubuntu/ karmic-updates main restricted universe multiverse deb-src http://ubuntu.srt.cn/ubuntu/ karmic-proposed main restricted universe multiverse deb-src http://ubuntu.srt.cn/ubuntu/ karmic-backports main restricted universe multiverse deb http://mirror.lupaworld.com/ubuntu/ubuntu-cn karmic main restricted universe multiverse
Archive.ubuntu.com更新服务器
deb http://archive.ubuntu.com/ubuntu/ karmic main restricted universe multiverse deb http://archive.ubuntu.com/ubuntu/ karmic-security main restricted universe multiverse deb http://archive.ubuntu.com/ubuntu/ karmic-updates main restricted universe multiverse deb http://archive.ubuntu.com/ubuntu/ karmic-proposed main restricted universe multiverse deb http://archive.ubuntu.com/ubuntu/ karmic-backports main restricted universe multiverse deb-src http://archive.ubuntu.com/ubuntu/ karmic main restricted universe multiverse deb-src http://archive.ubuntu.com/ubuntu/ karmic-security main restricted universe multiverse deb-src http://archive.ubuntu.com/ubuntu/ karmic-updates main restricted universe multiverse deb-src http://archive.ubuntu.com/ubuntu/ karmic-proposed main restricted universe multiverse deb-src http://archive.ubuntu.com/ubuntu/ karmic-backports main restricted universe multiverse
Mirrors.shlug.org更新服务器
deb http://cn.archive.ubuntu.com/ubuntu karmic main restricted universe multiverse deb http://cn.archive.ubuntu.com/ubuntu karmic-security main restricted universe multiverse deb http://cn.archive.ubuntu.com/ubuntu karmic-updates main restricted universe multiverse deb http://cn.archive.ubuntu.com/ubuntu karmic-backports main restricted universe multiverse deb http://cn.archive.ubuntu.com/ubuntu karmic-proposed main restricted universe multiverse deb-src http://cn.archive.ubuntu.com/ubuntu karmic main restricted universe multiverse deb-src http://cn.archive.ubuntu.com/ubuntu karmic-security main restricted universe multiverse deb-src http://cn.archive.ubuntu.com/ubuntu karmic-updates main restricted universe multiverse deb-src http://cn.archive.ubuntu.com/ubuntu karmic-backports main restricted universe multiverse deb-src http://cn.archive.ubuntu.com/ubuntu karmic-proposed main restricted universe multiverse
Mirror.lupaworld.com更新服务器
deb http://mirror.lupaworld.com/ubuntu karmic main restricted universe multiverse deb http://mirror.lupaworld.com/ubuntu karmic-security main restricted universe multiverse deb http://mirror.lupaworld.com/ubuntu karmic-updates main restricted universe multiverse deb http://mirror.lupaworld.com/ubuntu karmic-backports main restricted universe multiverse deb http://mirror.lupaworld.com/ubuntu karmic-proposed main restricted universe multiverse deb-src http://mirror.lupaworld.com/ubuntu karmic main restricted universe multiverse deb-src http://mirror.lupaworld.com/ubuntu karmic-security main restricted universe multiverse deb-src http://mirror.lupaworld.com/ubuntu karmic-updates main restricted universe multiverse deb-src http://mirror.lupaworld.com/ubuntu karmic-backports main restricted universe multiverse deb-src http://mirror.lupaworld.com/ubuntu karmic-proposed main restricted universe multiverse
ubuntu 10.04源
deb http://mirrors.163.com/ubuntu/ lucid main universe restricted multiverse deb-src http://mirrors.163.com/ubuntu/ lucid main universe restricted multiverse deb http://mirrors.163.com/ubuntu/ lucid-security universe main multiverse restricted deb-src http://mirrors.163.com/ubuntu/ lucid-security universe main multiverse restricted deb http://mirrors.163.com/ubuntu/ lucid-updates universe main multiverse restricted deb http://mirrors.163.com/ubuntu/ lucid-proposed universe main multiverse restricted deb-src http://mirrors.163.com/ubuntu/ lucid-proposed universe main multiverse restricted deb http://mirrors.163.com/ubuntu/ lucid-backports universe main multiverse restricted deb-src http://mirrors.163.com/ubuntu/ lucid-backports universe main multiverse restricted deb-src http://mirrors.163.com/ubuntu/ lucid-updates universe main multiverse restricted
以下为充字数内容
Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Venenatis cras sed felis eget velit aliquet sagittis id. Sed tempus urna et pharetra. Donec ultrices tincidunt arcu non sodales neque sodales ut etiam. Parturient montes nascetur ridiculus mus mauris vitae ultricies leo integer. Id consectetur purus ut faucibus pulvinar elementum integer enim. Purus non enim praesent elementum facilisis leo vel fringilla. Quis hendrerit dolor magna eget est lorem ipsum dolor sit. Fusce id velit ut tortor pretium viverra. Orci nulla pellentesque dignissim enim sit amet venenatis. Volutpat odio facilisis mauris sit amet massa vitae tortor condimentum. Sed arcu non odio euismod. Interdum varius sit amet mattis. Venenatis a condimentum vitae sapien pellentesque habitant morbi tristique senectus. Urna cursus eget nunc scelerisque viverra mauris in. Congue nisi vitae suscipit tellus mauris. Et sollicitudin ac orci phasellus egestas tellus rutrum tellus.
Lectus vestibulum mattis ullamcorper velit sed ullamcorper. Elit at imperdiet dui accumsan sit amet nulla. Feugiat in ante metus dictum. Dis parturient montes nascetur ridiculus mus. Nunc mattis enim ut tellus elementum sagittis vitae et leo. Ultricies mi eget mauris pharetra. Felis eget velit aliquet sagittis id consectetur purus. Turpis egestas integer eget aliquet nibh praesent tristique magna sit. Feugiat nisl pretium fusce id velit ut tortor pretium. Tristique risus nec feugiat in fermentum posuere urna nec tincidunt. Non arcu risus quis varius quam quisque. Libero volutpat sed cras ornare. Posuere lorem ipsum dolor sit. Dolor purus non enim praesent elementum facilisis leo. Mauris a diam maecenas sed enim ut.
Elementum pulvinar etiam non quam lacus suspendisse faucibus interdum. Et netus et malesuada fames. Dui id ornare arcu odio ut sem nulla. Proin libero nunc consequat interdum varius sit. Quam nulla porttitor massa id neque aliquam vestibulum morbi. Ut tristique et egestas quis ipsum suspendisse. A arcu cursus vitae congue mauris. Ut porttitor leo a diam sollicitudin tempor. Tortor dignissim convallis aenean et tortor at. Ac feugiat sed lectus vestibulum mattis ullamcorper velit sed ullamcorper. Habitasse platea dictumst quisque sagittis purus sit.
Semper viverra nam libero justo laoreet sit amet cursus sit. Vel orci porta non pulvinar neque. Maecenas sed enim ut sem viverra aliquet eget sit. Netus et malesuada fames ac turpis egestas integer eget aliquet. Sit amet mattis vulputate enim nulla aliquet porttitor lacus luctus. A cras semper auctor neque vitae tempus quam pellentesque. Ultrices vitae auctor eu augue ut lectus arcu. Id velit ut tortor pretium viverra suspendisse potenti nullam ac. Et malesuada fames ac turpis egestas integer eget aliquet nibh. Egestas fringilla phasellus faucibus scelerisque eleifend donec. At tellus at urna condimentum mattis pellentesque id nibh tortor. Dolor magna eget est lorem ipsum dolor sit. Eget mi proin sed libero enim. Aliquam ultrices sagittis orci a scelerisque purus semper eget duis. Tellus rutrum tellus pellentesque eu tincidunt tortor aliquam.
Felis eget velit aliquet sagittis id consectetur purus ut. Vitae proin sagittis nisl rhoncus mattis rhoncus urna neque. Non quam lacus suspendisse faucibus interdum. Elit scelerisque mauris pellentesque pulvinar. Habitasse platea dictumst vestibulum rhoncus est pellentesque. Eu ultrices vitae auctor eu. Viverra suspendisse potenti nullam ac tortor vitae purus. Nulla pellentesque dignissim enim sit amet venenatis urna cursus eget. Lectus sit amet est placerat in egestas erat imperdiet sed. Gravida neque convallis a cras semper auctor neque vitae. Morbi non arcu risus quis varius quam quisque id diam. Quam quisque id diam vel quam elementum pulvinar. Ullamcorper eget nulla facilisi etiam dignissim diam quis enim. Vel elit scelerisque mauris pellentesque pulvinar pellentesque habitant. Vitae congue eu consequat ac felis donec et odio. In nulla posuere sollicitudin aliquam ultrices sagittis orci a. Ligula ullamcorper malesuada proin libero nunc. Maecenas pharetra convallis posuere morbi leo urna. Ut consequat semper viverra nam libero. Sit amet cursus sit amet dictum sit.
乱数假文，英文又称“Lorem ipsum”，是指一篇常用于排版设计领域的文章，主要的目的为测试文章或文字在不同字型、版型下看起来的效果，通常网站还没建设好时会出现这段文字。
乱数假文生成器用来生成一篇用于排版设计领域的随机文章，支持生成英文、简体中文、繁体中文的乱数假文。
乱数假文相关介绍
Lorem ipsum从西元15世纪开始就被广泛地使用在西方的印刷、设计领域中，在电脑排版盛行之后，这段被传统印刷产业使用几百年的无意义文字又再度流行。由于这段文字以“Lorem ipsum”起头，并且常被用于标题的测试中，所以一般称为Lorem ipsum，简称为Lipsum。
网站没有建设完时，也会出现这样的段落，甚至有些是故意的，包括使用网页制作软件，网页模板等，新建时一般都会出现Lorem ipsum段落
常见的Lorem ipsum起头如下：
Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.
原先大家以为这段拉丁文只是没有意义的组合，目的是让阅读者不要被文章内容所影响，而只专注于观察字型或版型，并借此填满空间。但根据美国拉丁学者Richard McClintock的研究，Lorem ipsum原来起源于西塞罗的《善恶之尽》（De finibus bonorum et malorum）：
Neque porro quisquam est qui dolorem ipsum quia dolor sit amet, consectetur, adipisci velit…
（中译：无人爱苦，亦无人寻之欲之，乃因其苦…）
为了减少Lorem ipsum的可读性，并且让字母出现的频率与现代英语接近，所以有些版本中部分字母被K、W、Z等拉丁文中没有的字母替换，或是加入zzril、takimata等字。除了原始的Lorem ipsum版本外，还有几套新的Lorem ipsum。
