1 、安装完 CentOS 5.3 之后，首先要保证可以上网，安装完 SSH ，并且打开。
2 、设置软件源
1 ）、 CentOS 的网络源配置文件是：
/etc/yum.repos.d/ 下的 CentOS-Base.repo
本文提供其 5.3 版本的：网通，电信，第三方，163 源各一个
配置方法一般是：
① . 进入到repos.d 目录
$ cd /etc/yum.repos.d
$ ls -l
总计 24
-rw-r--r-- 1 root root 802 2009-09-02 CentOS-Base.repo
-rw-r--r-- 1 root root 626 03-17 09:30 CentOS-Media.repo
② . 备份原来的源
$ mv CentOS-Base.repo CentOS-Base.repo.backup
③ . 用下面的内容，重新生成CentOS-Base.repo
④ .$ yum update
2 ）、广泛应用的 CentOS 的软件源
① . 国内某大学源（电信网通皆可使用）
[base]
name=CentOS-5 – Base
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever5&arch=$basearch&repo=os
#baseurl=http://mirror.centos.org/centos/$releasever/os/$basearch/
baseurl=http://ftp.sjtu.edu.cn/centos/5.3/os/$basearch/
gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-centos6
#released updates
[update]
name=CentOS-5 – Updates
#mirrorlist=http://mirrorlist.centos.org/?release=4&arch=$basearch&repo=updates
baseurl=http://ftp.sjtu.edu.cn/centos/5.3/updates/$basearch/
gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-centos5
#packages used/produced in the build but not released
[addons]
name=CentOS-5 – Addons
#mirrorlist=http://mirrorlist.centos.org/?release=4&arch=$basearch&repo=addons
baseurl=http://ftp.sjtu.edu.cn/centos/5.3/addons/$basearch/
② . 国内电信源
# CentOS-Base.repo
#
# This file uses a new mirrorlist system developed by Lance Davis for CentOS.
# The mirror system uses the connecting IP address of the client and the
# update status of each mirror to pick mirrors that are updated to and
# geographically close to the client. You should use this for CentOS updates
# unless you are manually picking other mirrors.
#
# If the mirrorlist= does not work for you, as a fall back you can try the
# remarked out baseurl= line instead.
#
#
[base]
name=CentOS-$releasever – Base
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