推荐使用CentOS系统及下载（添加国内镜像源）
转载自：www.linuxtone.org
CentOS是Linux的一个发行版。

特点：
＝＝＝
1、可以把CentOS理解为Red Hat AS系列！它完全就是对Red Hat AS进行改进后发布的！各种操作、使用和RED HAT没有区别！

2、CentOS完全免费，不存在RED HAT AS4需要序列号的问题。

3、CentOS独有的yum命令支持在线升级，可以即时更新系统，不像RED HAT那样需要花钱购买支持服务！

4、CentOS修正了许多RED HAT AS的BUG！

呵呵，保留了RED HAT AS的优势，去掉了RED HAT AS 的限制，为什么不用CentOS呢？

附：
1、CentOS版本说明：
CentOS3.1 等同于 RED HAT AS3 Update1
CentOS3.4 等同于 RED HAT AS3 Update4
CentOS4.0 等同于 RED HAT AS4
…………………
2、CentOS 主页
http://www.centos.org

3、CentOS5.1 ISO文件下载:
http://mirror.nsc.liu.se/CentOS/5.1/isos/i386/
http://mirror.be10.com/centos/5.1/isos/

添加国内镜像源
一、CentOS国内镜像源下载
1、备份/etc/yum.repos.d/CentOS-Base.repo文件
＃vi /etc/yum.repos.d/CentOS-Base.repo 填入如下内容

代码:

[base]
name=CentOS-$releasever - Base
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=os
baseurl=http://mirror.be10.com/centos/$releasever/os/$basearch/
gpgcheck=1
gpgkey=http://mirror.be10.com/centos/RPM-GPG-KEY-CentOS-5

#released updates
[updates]
name=CentOS-$releasever - Updates
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=updates
baseurl=http://mirror.be10.com/centos/$releasever/updates/$basearch/
gpgcheck=1
gpgkey=http://mirror.be10.com/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=$basearch&repo=addons
baseurl=http://mirror.be10.com/centos/$releasever/addons/$basearch/
gpgcheck=1
gpgkey=http://mirror.be10.com/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=$basearch&repo=extras
baseurl=http://mirror.be10.com/centos/$releasever/extras/$basearch/
gpgcheck=1
gpgkey=http://mirror.be10.com/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=$basearch&repo=centosplus
baseurl=http://mirror.be10.com/centos/$releasever/centosplus/$basearch/
gpgcheck=1
enabled=0
gpgkey=http://mirror.be10.com/centos/RPM-GPG-KEY-CentOS-5
2、执行
rpm –import http://mirror.be10.com/centos/RPM-GPG-KEY-CentOS-5

二、CentOS 下使用本地镜像源

如果你已经下载了centos的DVD或者多CD版本，那好办，解压i386目录到本地的目录，比如/pkgstore/CentOS而CentOS已经 在/etc/yum.repos.d下面创建了CentOS-Media.repo，对该文件做适应修改就可以使用。以下是修改结果
[root@localhost etc]# cat yum.repos.d/CentOS-Media.repo
# CentOS-Media.repo
#
# This repo is used to mount the default locations for a CDROM / DVD on
# CentOS-5. You can use this repo and yum to install items directly off the
# DVD ISO that we release.
#
# To use this repo, put in your DVD and use it with the other repos to
# yum –enablerepo=c4-media [command]
#
# or for ONLY the media repo, do this:
#
# yum –disablerepo=\* –enablerepo=c4-media [command]

[c5-media]
name=CentOS-$releasever - Media
baseurl=file:///pkgstore/CentOS
# file:///media/cdrom/
# file:///media/cdrecorder/
gpgcheck=1
enabled=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-beta

现在就可以使用yum check-update来测验一下本地源了。如果在没有连接网络情况，最好把yum.repos.d目录下面的其它repo文件适当更名，这样yum就只使用本地源，速度得以提升。
补充：

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://mirror.be10.com/centos/

http://centos.candishosting.com.cn/

http://ftp.sjtu.edu.cn/centos/

http://ftp.hostrino.com/pub/centos/

http://mirrors.ta139.com/centos/

http://ftp.iasi.roedu.net/mirrors/centos.org/centos/
首先备份CentOS-Base.repo，然后再编辑 yum 的配置文件
[admingu@googe ~]$ sudo cp /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.bak
[admingu@googe ~]$ 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/$basearch/
baseurl=http://centos.candishosting.com.cn/$releasever/os/$basearch/
http://mirrors.ta139.com/centos/$releasever/os/$basearch/
http://mirror.be10.com/centos/$releasever/os/$basearch/
http://ftp.sjtu.edu.cn/centos/$releasever/os/$basearch/
http://ftp.hostrino.com/pub/centos/$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/$basearch/
baseurl=http://centos.candishosting.com.cn/$releasever/updates/$basearch/
http://mirrors.ta139.com/centos/$releasever/updates/$basearch/
http://mirror.be10.com/centos/$releasever/updates/$basearch/
http://ftp.sjtu.edu.cn/centos/$releasever/updates/$basearch/
http://ftp.hostrino.com/pub/centos/$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/$basearch/
baseurl=http://centos.candishosting.com.cn/$releasever/addons/$basearch/
http://mirrors.ta139.com/centos/$releasever/addons/$basearch/
http://mirror.be10.com/centos/$releasever/addons/$basearch/
http://ftp.sjtu.edu.cn/centos/$releasever/addons/$basearch/
http://ftp.hostrino.com/pub/centos/$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/$basearch/
baseurl=http://centos.candishosting.com.cn/$releasever/extras/$basearch/
http://mirrors.ta139.com/centos/$releasever/extras/$basearch/
http://mirror.be10.com/centos/$releasever/extras/$basearch/
http://ftp.sjtu.edu.cn/centos/$releasever/extras/$basearch/
http://ftp.hostrino.com/pub/centos/$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/$basearch/
baseurl=http://centos.candishosting.com.cn/$releasever/centosplus/$basearch/
http://mirrors.ta139.com/centos/$releasever/centosplus/$basearch/
http://mirror.be10.com/centos/$releasever/centosplus/$basearch/
http://ftp.sjtu.edu.cn/centos/$releasever/centosplus/$basearch/
http://ftp.hostrino.com/pub/centos/$releasever/centosplus/$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/$basearch/
baseurl=http://centos.candishosting.com.cn/$releasever/contrib/$basearch/
http://mirrors.ta139.com/centos/$releasever/contrib/$basearch/
http://mirror.be10.com/centos/$releasever/contrib/$basearch/
http://ftp.sjtu.edu.cn/centos/$releasever/contrib/$basearch/
http://ftp.hostrino.com/pub/centos/$releasever/contrib/$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：
[admingu@googe ~]$ 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。
[admingu@googe ~]$ sudo wget http://dag.wieers.com/rpm/packag ... 6-1.el5.rf.i386.rpm
[admingu@googe ~]$ sudo rpm -ivh rpmforge-release-0.3.6-1.el5.rf.i386.rpm
[admingu@googe ~]$ 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。
II、添加DAG更新仓库。
1)在/etc/yum.repos.d/下建立dag.repo
2)编辑dag.repo
[admingu@googe ~]$ sudo vi /etc/yum.repos.d/dag.repo
[dag]
name=Dag RPM Repository for Red Hat Enterprise Linux
baseurl=http://apt.sw.be/redhat/el5/en/i386/dag
gpgcheck=1
enabled=1
gpgkey=http://dag.wieers.com/rpm/packages/RPM-GPG-KEY.dag.txt

保存退出。
然后导入Key,
[admingu@googe ~]$ sudo rpm --import http://dag.wieers.com/rpm/packages/RPM-GPG-KEY.dag.txt
添加DAG可能会有点问题，这要看所在网速如何？
三、使用如下命令更新到最新系统
# yum upgrade
四、安装必要的软件工具
# yum install wget bzip2 unzip zip nmap tree lynx fileutils ncftp lftp
若您需要在本机编译源代码的软件，请安装开发工具组的软件包
# yum groupinstall "Development Tools"
追加新源地址：
[base]
name=CentOS-5 - Base
baseurl=http://centos.ustc.edu.cn/centos/5/os/$basearch/
gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-5

#released updates
[update]
name=CentOS-5 - Updates
baseurl=http://centos.ustc.edu.cn/centos/5/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-5 - Addons
baseurl=http://centos.ustc.edu.cn/centos/5/addons/$basearch/
gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-5
#additional packages that may be useful
[extras]
name=CentOS-5 - Extras
baseurl=http://centos.ustc.edu.cn/centos/5/extras/$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-5 - Plus
baseurl=http://centos.ustc.edu.cn/centos/5/centosplus/$basearch/
gpgcheck=1
enabled=0
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-5

#contrib - packages by Centos Users
[contrib]
name=CentOS-5 - Contrib
baseurl=http://centos.ustc.edu.cn/centos/5/contrib/$basearch/
gpgcheck=1
enabled=0
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-5

#packages in testing
[testing]
name=CentOS-5 - Testing
baseurl=http://centos.ustc.edu.cn/centos/5/testing/$basearch/
gpgcheck=1
enabled=0
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-5