BirdSky

使用yum更新或者安装软件时，有时下载速度会很慢，这时可以安装自动选择最快源的插件yum-fastestmirror。
yum install yum-fastestmirror

装上之后，在yum更新或者安装时，它会自动选择最快的源来下载，如果你对它选择的源不满意，只要Ctrl+c一下，它就会自动更换一个源来下载了，如果新换的源还是慢，就再Ctrl+c一下，接着换，直到换到快的为止。

注意：千万别一次连着按几下Ctrl+c，那样会直接退出yum安装了。

yum虽然很好用，但却有一个小问题，那就是更新速度。对于国内用户，尤其是你的网速还不够快的时候，使用yum意味着漫长的等待。我搜集了几个速度不错的国内源，大家可以自己选择、测试、修改。需要修改的文件是/etc/yum.repos.d/CentOS-Base.repo，记得备份！

首先，备份原yum源
cd /etc/yum.repos.d/
cp CentOS-Base.repo CentOS-Base.repo.bak
然后在下面的源中选择一个来用
vi CentOS-Base.repo
最后更新缓存
yum makecache

以下为收集到的源
1.默认的CentOS-Base.repo文件:

CentOS-Base.repo
# CentOS-Base.repo  
#  
# This file uses a new mirrorlist system developed by Lance Davis for CentOS.  
# The mirror system uses the connecting IP address of the client and the  
# update status of each mirror to pick mirrors that are updated to and  
# geographically close to the client.  You should use this for CentOS updates  
# unless you are manually picking other mirrors.  
#  
# If the mirrorlist= does not work for you, as a fall back you can try the    
# remarked out baseurl= line instead.  
#  
#  
 
[base]  
name=CentOS-$releasever - Base  
mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=os  
#baseurl=http://mirror.centos.org/centos/$releasever/os/$basearch/  
gpgcheck=1  
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-5  
priority=1  
 
#released updates    
[updates]  
name=CentOS-$releasever - Updates  
mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=updates  
#baseurl=http://mirror.centos.org/centos/$releasever/updates/$basearch/  
gpgcheck=1  
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-5  
priority=1  
 
#packages used/produced in the build but not released  
[addons]  
name=CentOS-$releasever - Addons  
mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=addons  
#baseurl=http://mirror.centos.org/centos/$releasever/addons/$basearch/  
gpgcheck=1  
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-5  
priority=1  
 
#additional packages that may be useful  
[extras]  
name=CentOS-$releasever - Extras  
mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=extras  
#baseurl=http://mirror.centos.org/centos/$releasever/extras/$basearch/  
gpgcheck=1  
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-5  
priority=1  
 
#additional packages that extend functionality of existing packages  
[centosplus]  
name=CentOS-$releasever - Plus  
mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=centosplus  
#baseurl=http://mirror.centos.org/centos/$releasever/centosplus/$basearch/  
gpgcheck=1  
enabled=0  
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-5  
priority=2  

2.USTC源
该源由中国科学技术大学提供，合肥电信，每小时更新，CentOS官方镜像。编辑CentOS-Base.repo内容如下，下同。

USTC
[base]  
name=CentOS-$releasever - Base  
baseurl=http://centos.ustc.edu.cn/centos/$releasever/os/$basearch/  
gpgcheck=1  
gpgkey=http://centos.ustc.edu.cn/centos/RPM-GPG-KEY-CentOS-5  
 
[updates]  
name=CentOS-$releasever - Updates  
baseurl=http://centos.ustc.edu.cn/centos/$releasever/updates/$basearch/  
gpgcheck=1  
gpgkey=http://centos.ustc.edu.cn/centos/RPM-GPG-KEY-CentOS-5  
 
[addons]  
name=CentOS-$releasever - Addons  
baseurl=http://centos.ustc.edu.cn/centos/$releasever/addons/$basearch/  
gpgcheck=1  
gpgkey=http://centos.ustc.edu.cn/centos/RPM-GPG-KEY-CentOS-5  
 
[extras]  
name=CentOS-$releasever - Extras  
baseurl=http://centos.ustc.edu.cn/centos/$releasever/extras/$basearch/  
gpgcheck=1  
gpgkey=http://centos.ustc.edu.cn/centos/RPM-GPG-KEY-CentOS-5  
 
[centosplus]  
name=CentOS-$releasever - Plus  
baseurl=http://centos.ustc.edu.cn/centos/$releasever/centosplus/$basearch/  
gpgcheck=1  
enabled=0  
gpgkey=http://centos.ustc.edu.cn/centos/RPM-GPG-KEY-CentOS-5  

3.mirror.centos.net.cn源
该源同样为CentOS官方镜像，属于北京网通，北方网通用户推荐。

mirror.centos.net.cn
[base]  
name=CentOS-$releasever - Base  
baseurl=http://mirror.centos.net.cn/$releasever/os/$basearch/  
gpgcheck=1  
gpgkey=http://mirror.centos.net.cn/RPM-GPG-KEY-CentOS-5  
 
[update]  
name=CentOS-$releasever - Updates  
baseurl=http://mirror.centos.net.cn/$releasever/updates/$basearch/  
gpgcheck=1  
gpgkey=http://mirror.centos.net.cn/RPM-GPG-KEY-CentOS-5  
 
[addons]  
name=CentOS-$releasever - Addons  
baseurl=http://mirror.centos.net.cn/$releasever/addons/$basearch/  
gpgcheck=1  
gpgkey=http://mirror.centos.net.cn/RPM-GPG-KEY-CentOS-5  
 
[extras]  
name=CentOS-$releasever - Extras  
baseurl=http://mirror.centos.net.cn/$releasever/extras/$basearch/  
gpgcheck=1  
gpgkey=http://mirror.centos.net.cn/RPM-GPG-KEY-CentOS-5  
 
[centosplus]  
name=CentOS-$releasever - Plus  
baseurl=http://mirror.centos.net.cn/$releasever/centosplus/$basearch/  
gpgcheck=1  
enabled=1  
gpgkey=http://mirror.centos.net.cn/RPM-GPG-KEY-CentOS-5  
 
[contrib]  
name=CentOS-$releasever - Contrib  
baseurl=http://mirror.centos.net.cn/$releasever/contrib/$basearch/  
gpgcheck=1  
enabled=0  
gpgkey=http://mirror.centos.net.cn/RPM-GPG-KEY-CentOS-5  

4.网易源
http://mirrors.163.com, 该源由网易提供，杭州电信。下载CentOS-Base-163.repo, 放入/etc/yum.repos.d/，然后运行yum makecache生成缓存。

NETEASE:mirrors.163.com
[base]  
name=CentOS-$releasever - Base  
baseurl=http://mirrors.163.com/centos/$releasever/os/$basearch/  
gpgcheck=1  
gpgkey=http://mirrors.163.com/centos/RPM-GPG-KEY-CentOS-5  
 
[update]  
name=CentOS-$releasever - Updates  
baseurl=http://mirrors.163.com/centos/$releasever/updates/$basearch/  
gpgcheck=1  
gpgkey=http://mirrors.163.com/centos/RPM-GPG-KEY-CentOS-5  
 
[addons]  
name=CentOS-$releasever - Addons  
baseurl=http://mirrors.163.com/centos/$releasever/addons/$basearch/  
gpgcheck=1  
gpgkey=http://mirrors.163.com/centos/RPM-GPG-KEY-CentOS-5  
 
[extras]  
name=CentOS-$releasever - Extras  
baseurl=http://mirrors.163.com/centos/$releasever/extras/$basearch/  
gpgcheck=1  
gpgkey=http://mirrors.163.com/centos/RPM-GPG-KEY-CentOS-5  
 
[centosplus]  
name=CentOS-$releasever - Plus  
baseurl=http://mirrors.163.com/centos/$releasever/centosplus/$basearch/  
gpgcheck=1  
enabled=1  
gpgkey=http://mirrors.163.com/centos/RPM-GPG-KEY-CentOS-5  
 
[contrib]  
name=CentOS-$releasever - Contrib  
baseurl=http://mirrors.163.com/centos/$releasever/contrib/$basearch/  
gpgcheck=1  
enabled=0  
gpgkey=http://mirrors.163.com/centos/RPM-GPG-KEY-CentOS-5  

5.搜狐源
http://mirrors.sohu.com ,该源由搜狐提供，山东联通。下载CentOS-Base-sohu.repo, 放入/etc/yum.repos.d/，然后运行yum makecache生成缓存。

SOHU:mirrors.sohu.com
[base]  
name=CentOS-$releasever - Base  
baseurl=http://mirrors.sohu.com/centos/$releasever/os/$basearch/  
gpgcheck=1  
gpgkey=http://mirrors.sohu.com/centos/RPM-GPG-KEY-CentOS-5  
 
[update]  
name=CentOS-$releasever - Updates  
baseurl=http://mirrors.sohu.com/centos/$releasever/updates/$basearch/  
gpgcheck=1  
gpgkey=http://mirrors.sohu.com/centos/RPM-GPG-KEY-CentOS-5  
 
[addons]  
name=CentOS-$releasever - Addons  
baseurl=http://mirrors.sohu.com/centos/$releasever/addons/$basearch/  
gpgcheck=1  
gpgkey=http://mirrors.sohu.com/centos/RPM-GPG-KEY-CentOS-5  
 
[extras]  
name=CentOS-$releasever - Extras  
baseurl=http://mirrors.sohu.com/centos/$releasever/extras/$basearch/  
gpgcheck=1  
gpgkey=http://mirrors.sohu.com/centos/RPM-GPG-KEY-CentOS-5  
 
[centosplus]  
name=CentOS-$releasever - Plus  
baseurl=http://mirrors.sohu.com/centos/$releasever/centosplus/$basearch/  
gpgcheck=1  
enabled=1  
gpgkey=http://mirrors.sohu.com/centos/RPM-GPG-KEY-CentOS-5  
 
[contrib]  
name=CentOS-$releasever - Contrib  
baseurl=http://mirrors.sohu.com/centos/$releasever/contrib/$basearch/  
gpgcheck=1  
enabled=0  
gpgkey=http://mirrors.sohu.com/centos/RPM-GPG-KEY-CentOS-5  

     在 64位版本的 CentOS 5.4 上使用 yum 安装软件包的时候如果不小心的话会同时安装 i386 和 x86_64 版本的软件。同时安装32位和64位版本的软件虽然不是什么错，也不会对系统造成什么问题，但是这样会浪费硬盘空间，而且显得系统臃肿、不干净。如果想要保持一个纯的64位系统、在64位 CentOS 上避免安装32位软件包的话很容易，只需要在 yum.conf 加上一行过滤掉 i386, i686 的软件包就可以了：

# vi /etc/yum.conf

[main]
...
exclude=*.i386 *.i686