在CentOS系统中，yum是个好东东，几乎大部分流行的组件都可以直接通过yum来安装，但系统默认的yum源速度往往不尽人意，而fastest mirror插件，有时候用起来并不是很适用，为了达到快递安装的目的，我们需要修改默认的yum源
中科大的Centos 开源镜像站点. http://centos.ustc.edu.cn/
执行以下命令就可以了
cd /etc/yum.repos.d
mv CentOS-Base.repo CentOS-Base.repo.bak
wget http://centos.ustc.edu.cn/CentOS-Base.repo.5
mv CentOS-Base.repo.5 CentOS-Base.repo
cat CentOS-Base.repo
[base]
name=CentOS-$releasever – Base
baseurl=http://centos.ustc.edu.cn/centos/$releasever/os/$basearch/
gpgcheck=1
gpgkey=http://centos.ustc.edu.cn/centos/RPM-GPG-KEY-CentOS-5
#released updates
[updates]
name=CentOS-$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
#packages used/produced in the build but not released
[addons]
name=CentOS-$releasever – Addons
baseurl=http://centos.ustc.edu.cn/centos/$releasever/addons/$basearch/
gpgcheck=1
gpgkey=http://centos.ustc.edu.cn/centos/RPM-GPG-KEY-CentOS-5
#additional packages that may be useful
[extras]
name=CentOS-$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
#additional packages that extend functionality of existing packages
[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
也可以使用，http://mirrors.163.com/ http://mirrors.sohu.com，电信用户使用163的镜像速度会比较快。