CentOS 安装完毕，首先应该修改更新源，并升级到最新的系统。国内速度比较快的更新源，我推荐：http://mirrors.163.com 网易的更新源，刚发现的，速度还可以。
首先我们得先备份系统先前的配置文件CentOS-Base.repo：sudo cp /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.bak编辑yum的配置文件：sudo vi /etc/yum.repos.d/CentOS-Base.repo
把CenOS-Base-repo内文件的中的mirrorlist注释掉，然后把baseurl前的注释去掉，然后把源地址改为网易的
配置文件的内容为：
[base]name=CentOS-$releasever - Base#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=osbaseurl=http://mirrors.163.com/centos/$releasever/os/$basearch/gpgcheck=1gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-5#released updates[updates]name=CentOS-$releasever - Updates#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=updatesbaseurl=http://mirrors.163.com/centos/$releasever/updates/$basearch/gpgcheck=1gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-5#packages used/produced in the build but not released[addons]name=CentOS-$releasever - Addons#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=addonsbaseurl=http://mirrors.163.com/centos/$releasever/addons/$basearch/gpgcheck=1gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-5#additional packages that may be useful[extras]name=CentOS-$releasever - Extras#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=extrasbaseurl=http://mirrors.163.com/centos/$releasever/extras/$basearch/gpgcheck=1gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-5#additional packages that extend functionality of existing packages[centosplus]name=CentOS-$releasever - Plus#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=centosplusbaseurl=http://mirrors.163.com/centos/$releasever/centosplus/$basearch/gpgcheck=1enabled=0gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-5#contrib - packages by Centos Users[contrib]name=CentOS-$releasever - Contrib#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=contribbaseurl=http://mirrors.163.com/centos/$releasever/contrib/$basearch/gpgcheck=1enabled=0gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-5
其中：
repositoryid:用于指定一个仓库
name：用于指定易读的仓库名称
baseurl：用于指定本仓库的URL，可以是以下的3种类型，如http,ftp,file
mirrorlist：用于指定仓库的镜像站点
enable：用于指定是否使用本仓库，默认值为1，即可用。
gpgcheck：用于指定是否检查软件包的GPG签名。
gpgkey：用于指定GPG签名文件的URL。
本人一般都是用root超级用户
如果是普通用户就在命令最前面加上sudo
执行命令：
rpm --import /etc/pki/rpm-gpg/RPM-GPG-KEY*
rpm update
相关资源：Redhat 使用CentOS的yum源进行升级或软件安装