今天晚上用官方源打算安装东西的时候发现速度偏慢，哎，这么不靠谱，这不是逼我投向别人的怀抱嘛。开了N个网页，总算搞清楚源是肿么回事了，果断码个总结！
一、软件源的描述
软件源就是一个应用程序安装库，很多很多的应用软件都在这个库里面。他可以是网络服务器，是光盘，甚至是硬盘上的一个目录。所以说要安装好软件且方便快捷，那首先得找到一个好的源，然后修改源文件更新下即可。
二、怎么修改源
源文件具体目录：/etc/apt/sources.list
我的Ubuntu版本是11.10，刚安装Ubuntu后sources.list文件内容如下：
1 #deb cdrom:[Ubuntu 11.10 _Oneiric Ocelot_ - Release i386 (20111012)]/ oneiric main restricted
2
3 # See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
4 # newer versions of the distribution.
5 deb http://us.archive.ubuntu.com/ubuntu/ oneiric main restricted
6 deb-src http://us.archive.ubuntu.com/ubuntu/ oneiric main restricted
7
8 ## Major bug fix updates produced after the final release of the
9 ## distribution.
10 deb http://us.archive.ubuntu.com/ubuntu/ oneiric-updates main restricted
11 deb-src http://us.archive.ubuntu.com/ubuntu/ oneiric-updates main restricted
12
13 ## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
14 ## team. Also, please note that software in universe WILL NOT receive any
15 ## review or updates from the Ubuntu security team.
16 deb http://us.archive.ubuntu.com/ubuntu/ oneiric universe
17 deb-src http://us.archive.ubuntu.com/ubuntu/ oneiric universe
18 deb http://us.archive.ubuntu.com/ubuntu/ oneiric-updates universe
19 deb-src http://us.archive.ubuntu.com/ubuntu/ oneiric-updates universe
20
21 ## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
22 ## team, and may not be under a free licence. Please satisfy yourself as to
23 ## your rights to use the software. Also, please note that software in
24 ## multiverse WILL NOT receive any review or updates from the Ubuntu
25 ## security team.
26 deb http://us.archive.ubuntu.com/ubuntu/ oneiric multiverse
27 deb-src http://us.archive.ubuntu.com/ubuntu/ oneiric multiverse
28 deb http://us.archive.ubuntu.com/ubuntu/ oneiric-updates multiverse
29 deb-src http://us.archive.ubuntu.com/ubuntu/ oneiric-updates multiverse
30
31 ## N.B. software from this repository may not have been tested as
32 ## extensively as that contained in the main release, although it includes
33 ## newer versions of some applications which may provide useful features.
34 ## Also, please note that software in backports WILL NOT receive any review
35 ## or updates from the Ubuntu security team.
36 deb http://us.archive.ubuntu.com/ubuntu/ oneiric-backports main restricted universe multiverse
37 deb-src http://us.archive.ubuntu.com/ubuntu/ oneiric-backports main restricted universe multiverse
38
39 deb http://security.ubuntu.com/ubuntu oneiric-security main restricted
40 deb-src http://security.ubuntu.com/ubuntu oneiric-security main restricted
41 deb http://security.ubuntu.com/ubuntu oneiric-security universe
42 deb-src http://security.ubuntu.com/ubuntu oneiric-security universe
43 deb http://security.ubuntu.com/ubuntu oneiric-security multiverse
44 deb-src http://security.ubuntu.com/ubuntu oneiric-security multiverse
45
46 ## Uncomment the following two lines to add software from Canonical's
47 ## 'partner' repository.
48 ## This software is not part of Ubuntu, but is offered by Canonical and the
49 ## respective vendors as a service to Ubuntu users.
50 # deb http://archive.canonical.com/ubuntu oneiric partner
51 # deb-src http://archive.canonical.com/ubuntu oneiric partner
52
53 ## This software is not part of Ubuntu, but is offered by third-party
54 ## developers who want to ship their latest software.
55 deb http://extras.ubuntu.com/ubuntu oneiric main
56 deb-src http://extras.ubuntu.com/ubuntu oneiric main
从文件内容我们可以看出官方源服务器位于美国，既然要找个速度快的，显然得换个国内的源嘛。由于国内源众多，据说163源蛮好，所以我选择了163的源；不过据说骨头源也蛮不错，不过我已经选择了163了，要专一啊！！反正好的源很多，看自己是电信的还是网通的，找个合适自己的最好！
OK，把原来的文件sources.list备份到sources.list-origin，我现在的sources.list的内容更换如下：
deb http://mirrors.163.com/ubuntu/ oneiric main restricted universe multiverse
deb http://mirrors.163.com/ubuntu/ oneiric-security main restricted universe multiverse
deb http://mirrors.163.com/ubuntu/ oneiric-updates main restricted universe multiverse
deb http://mirrors.163.com/ubuntu/ oneiric-proposed main restricted universe multiverse
deb http://mirrors.163.com/ubuntu/ oneiric-backports main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ oneiric main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ oneiric-security main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ oneiric-updates main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ oneiric-proposed main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ oneiric-backports main restricted universe multiverse
OK，接下来简要分析下sources.list的内容的意思，地址是http://mirrors.163.com/ubuntu/这个呢就是163的ubuntu源的服务器目录，这个目录下的内容我们还是要了解一下的，等会分析。然后有一个字符串引起我们的注意，而且至关重要，没错，就是：oneiric，这是Ubuntu 11.10的名字，具体有什么用还是等会带来讲解。
好的，接下来分析一下这个163服务器，进入这个服务器后(http://mirrors.163.com/ubuntu/)，我们进入dists目录，可以看到此时目录下内容为：
../
hardy/ 14-Oct-2011 15:23 -
hardy-backports/ 15-Jul-2012 14:54 -
hardy-proposed/ 21-Jul-2012 15:30 -
hardy-security/ 13-Jun-2012 15:09 -
hardy-updates/ 21-Jul-2012 15:30 -
lucid/ 14-Oct-2011 15:23 -
lucid-backports/ 18-Jul-2012 15:24 -
lucid-proposed/ 30-Jul-2012 14:57 -
lucid-security/ 18-Jul-2012 15:23 -
lucid-updates/ 22-Jul-2012 15:13 -
maverick/ 14-Oct-2011 15:23 -
maverick-backports/ 04-Apr-2012 14:59 -
maverick-proposed/ 04-Apr-2012 14:59 -
maverick-security/ 24-Mar-2012 14:57 -
maverick-updates/ 24-Mar-2012 14:57 -
natty/ 14-Oct-2011 15:23 -
natty-backports/ 03-May-2012 15:32 -
natty-proposed/ 31-Jul-2012 14:37 -
natty-security/ 18-Jul-2012 15:23 -
natty-updates/ 19-Jul-2012 15:18 -
oneiric/ 14-Oct-2011 15:22 -
oneiric-backports/ 04-Apr-2012 14:58 -
oneiric-proposed/ 01-Aug-2012 15:21 -
oneiric-security/ 18-Jul-2012 15:23 -
oneiric-updates/ 21-Jul-2012 15:29 -
precise/ 26-Apr-2012 14:30 -
precise-backports/ 16-Jul-2012 15:00 -
precise-proposed/ 01-Aug-2012 21:14 -
precise-security/ 01-Aug-2012 21:14 -
precise-updates/ 01-Aug-2012 21:14 -
quantal/ 01-Aug-2012 21:14 -
quantal-backports/ 27-Apr-2012 15:32 -
quantal-proposed/ 01-Aug-2012 21:14 -
quantal-security/ 27-Apr-2012 15:32 -
quantal-updates/ 27-Apr-2012 15:32 -
那这个内容对我们有什么用呢？我们可以看到里面有hardy，lucid，oneiric等，这些呢，就是Ubuntu版本代号。每个Ubuntu版本都是有版本名的，不清楚可以进入百科查看hardy对应的是Ubuntu 8.04，而lucid对应的是Ubuntu 10.04。不同版本要求的的源文件的内容也是不同的，所以需要看清楚。
在此目录中我们可以看到我们需要的版本11.10对应的源：oneiric，有了这个我们才能用163的源。
那假设我现在的Ubuntu版本是11.04，那我怎么修改sources.list的内容呢？很简单，首先我们知道11.04的英文名是natty，我们从这个服务器可以看到有natty的目录，那我们只需要把我刚更新的163的源文件中的oneiric改为natty，保存就可以了，方便吧！如果没有natty，那么显然修改了也找不到的，所以需要看清楚有没对应自己Ubuntu版本的源。
三、修改源后操作
经过上面的操作，现在已经换好源了，肯定要让它生效吧，按下面的步骤来即可：
1）sudo apt-get update #这一步是更新你的源列表，换源后必须执行
2）sudo apt-get dist-upgrade #这一步是更新软件
OK，换源完成，要安装什么东西输入"sudo apt-get install [软件名] "即可。而且速度蛮快！
本文完。