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== Downgrade ==
So, for one reason or another, you've upgraded Ubuntu to a new version. Now, you're not liking the new version (or it's a development version and too unstable for your taste). Downgrading is a little-covered topic, but let's change that!

=== DISCLAIMER ===
This document is still under development. I have *YET TO TEST THE PROCEDURE*. Please pursue at your own risk until this documentation is completed!

=== Getting Started ===
For this guide, we'll use the example of downgrading Ubuntu Breezy to Ubuntu Hoary. This guide can be adapted to downgrade any combination of releases.

=== The Procedure ===

==== Setting up sources ====
You'll need sources.list entries for both releases for the procedure to work properly. It's important to remove all other lines for now! Example sources.list:

<pre><nowiki>deb http://archive.ubuntu.com/ubuntu hoary main restricted universe multiverse

deb http://archive.ubuntu.com/ubuntu breezy main restricted universe multiverse</nowiki></pre>

==== Setting up pinning ====
Open up /etc/apt/preferences with your favorite editor (such as <code><nowiki>sudo gedit /etc/apt/preferences</nowiki></code>)

Add the following lines to the file (remove any existing entries):
<pre><nowiki>
Package: *
Pin: release a=hoary
Pin-Priority: 1001

Package: *
Pin: release a=breezy
Pin-Priority: 60
</nowiki></pre>

==== Doing the downgrade ====
If you're ready to continue, we're going to continue:

First, we need to update APT's information:
<code><nowiki>sudo apt-get update</nowiki></code>

Next, we'll downgrade:
<code><nowiki>sudo apt-get dist-upgrade</nowiki></code>

==== Cleaning up after the storm ====
The last step probably will end up a catastrophic mess of incompletely installed packages. We need to fix that now.
=== Sources ===
http://linuxmafia.com/faq/Debian/downgrade.html




== 降级 ==
出于某种原因，你将Ubuntu升级到了一个新的版本。可是，你发现你并不喜欢这个新版本(或者这个新版本是个尚未开发完毕的版本，并且它很不合你的口味)。尽管降级是个容易被忽略的主题，可是并非不能实现,现在就让我们来进行降级操作吧。

=== 不承诺声明 ===
这份文档仍然处于完善中。尽管我已经测试过程序了，但仍然有操作失败的风险。你需要衡量一下是否值得冒这个险直到这份操作文档彻底完成。

=== 开始操作 ===
在这份操作指南中，我们以Ubuntu Breezy降级到Ubuntu Hoary为例子来说明如何进行降级操作。这份操作指南适用于所有的发行版本的任意组合。

=== 脚本程序 ===

==== 设置源 ====
你需要设置一下sources.list的条目，只保留降级操作的始末的版本信息，以便能使降级操作得以运行。记住要将其他所有的行都去掉，这很重要。以下是一个sources.list的例子:

<pre><nowiki>deb http://archive.ubuntu.com/ubuntu hoary main restricted universe multiverse

deb http://archive.ubuntu.com/ubuntu breezy main restricted universe multiverse</nowiki></pre>

==== 设置销连接 ====
用编辑器(如gedit)打开/etc/apt/preferences (如 <code><nowiki>sudo gedit /etc/apt/preferences</nowiki></code>)

将下面这几行加入到这个文件中(记住先把其他的内容清除掉):
<pre><nowiki>
Package: *
Pin: release a=hoary
Pin-Priority: 1001

Package: *
Pin: release a=breezy
Pin-Priority: 60
</nowiki></pre>

==== 进行降级操作 ====
如果你准备好了，我们就继续我们的降级操作:

首先，我们需要升级APT的信息:
<code><nowiki>sudo apt-get update</nowiki></code>

然后，我们就开始降级:
<code><nowiki>sudo apt-get dist-upgrade</nowiki></code>

==== 操作失败后的修复工作 ====
我们操作的结果可能会变成安装不完全的悲惨结局，因此我们需要修复它。

翻译：norvid 2005-12-18
=== 转载自 ===
http://linuxmafia.com/faq/Debian/downgrade.html