一、使用更新源的国内镜像
CentOS 安装完毕，首先应该修改更新源，并升级到最新的系统。 国内速度较快的常用更新源：
http://centos.ustc.edu.cn/centos/ http://mirrors.163.com/centos/ http://mirrors.sohu.com/centos/
首先备份CentOS-Base.repo，然后再编辑 yum 的配置文件： [piaoyun@piaoyun-pc ~]$ sudo cp /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.bak [piaoyun@piaoyun-pc ~]$ sudo vi /etc/yum.repos.d/CentOS-Base.repo
[base]
name=CentOS-$releasever - Base
mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=os
baseurl=http://mirror.centos.org/centos/$releasever/os/$basearch/
http://centos.ustc.edu.cn/centos/$releasever/os/$basearch/
http://mirrors.163.com/centos/$releasever/os/$basearch/
http://mirrors.sohu.com/centos/$releasever/os/$basearch/
gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-5
#released updates
[updates]
name=CentOS-$releasever - Updates
mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=updates
baseurl=http://mirror.centos.org/centos/$releasever/updates/$basearch/
http://centos.ustc.edu.cn/centos/$releasever/updates/$basearch/
http://mirrors.163.com/centos/$releasever/updates/$basearch/
http://mirrors.sohu.com/centos/$releasever/updates/$basearch/
gpgcheck=1
gpgkey=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=$basearch&repo=addons
baseurl=http://mirror.centos.org/centos/$releasever/addons/$basearch/
http://centos.ustc.edu.cn/centos/$releasever/addons/$basearch/
http://mirrors.163.com/centos/$releasever/addons/$basearch/
http://mirrors.sohu.com/centos/$releasever/addons/$basearch/
gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-5
#additional packages that may be useful
[extras]
name=CentOS-$releasever - Extras
mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=extras
baseurl=http://mirror.centos.org/centos/$releasever/extras/$basearch/
http://centos.ustc.edu.cn/centos/$releasever/extras/$basearch/
http://mirrors.163.com/centos/$releasever/extras/$basearch/
http://mirrors.sohu.com/centos/$releasever/extras/$basearch/
gpgcheck=1
gpgkey=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=$basearch&repo=centosplus
baseurl=http://mirror.centos.org/centos/$releasever/centosplus/$basearch/
http://centos.ustc.edu.cn/centos/$releasever/centosplus/$basearch/
http://mirrors.163.com/centos/$releasever/extras/$basearch/
http://mirrors.sohu.com/centos/$releasever/extras/$basearch/
gpgcheck=1
enabled=0
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-5
#contrib - packages by Centos Users
[contrib]
name=CentOS-$releasever - Contrib
mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=contrib
baseurl=http://mirror.centos.org/centos/$releasever/contrib/$basearch/
http://ftp.sjtu.edu.cn/centos/$releasever/contrib/$basearch/
http://mirrors.163.com/centos/$releasever/extras/$basearch/
http://mirrors.sohu.com/centos/$releasever/extras/$basearch/
gpgcheck=1
enabled=0
gpgkey=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。 执行命令： [piaoyun@piaoyun-pc ~]$ sudo rpm --import /etc/pki/rpm-gpg/RPM-GPG-KEY*
二、使用非官方更新源
下面以安装rpmforge和DAG软件包为例添加非官方更新源 I、添加rmpforge软件库 1）到http://dag.wieers.com/rpm/packages/rpmforge-release/查找适用于RHEL5/CentOS5的软件包。 2）下载适用于RHEL5/CentOS5的软件包。 [piaoyun@piaoyun-pc ~]$ sudo wget http://dag.wieers.com/rpm/packages/rpmforge-release/rpmforge-release-0.3.6-1.el5.rf.i386.rpm [piaoyun@piaoyun-pc ~]$ sudo rpm -ivh rpmforge-release-0.3.6-1.el5.rf.i386.rpm [piaoyun@piaoyun-pc ~]$ sudo rpm --import /etc/pki/rpm-gpg/RPM-GPG-KEY-rpmforge-* 安装rpmforge-release软件包之后，就可以看到/etc/yum.repos.d/rpmforge.repo文件，以后yum就可以使用这个更新源了。
三、使用如下命令更新到最新系统：
yum check-update yum -y update yum upgrade 使用yum update更新时，默认会升级内核。但有些服务器硬件（特别是组装的机器）在升级内核后，新的内核可能会认不出某些硬件，要重新安装驱动，很麻烦。所以在生产环境中不要轻易的升级内核，除非你确定升级内核后不会出现麻烦的问题。
CentOS使用yum update升级时，默认包含升级内核！比如从CentOS 6.2升级到CentOS 6.4如果不想升级内核而只更新其他软件包，有两种方法： 1、修改yum的配置文件 vim /etc/yum.conf，在[main]的最后添加
exclude=kernel* centos-release*
2、直接在yum的命令后面加上如下的参数：
yum --exclude=kernel* centos-release* update
四、安装必要的软件工具
yum -y install --skip-broken yum-fastestmirror build-essential gcc gcc-c++ bzip2 make vixie-cron flex ncurses-devel wget patch ntp libxml2 libxml2-devel libevent m4 autoconf zip unzip libjpeg libjpeg-devel gd gd-devel freetype freetype-devel libpng libpng-devel openssl openssl-devel file libtool libtool-libs libtool-ltdl-devel gmp-devel pspell-devel parted zlib mod_perl-devel ftp readline-devel apr apr-util curl-devel pam pam-devel lynx libmcrypt-devel libmhash-devel sudo glibc glibc-devel perl perl*
