CentOS 5.5 yum 国内更新源

第1步
备份yum配置文件，修改yum配置文件。

cp /etc/yum.repos.d/CentOS-Base.repo CentOS-Base.repo_bak
vi /etc/yum.repo.d/CentOS-Base.repo
可以用中科大(ustc)yum源，也可以用上海交大(sjtu)yum源，两者只能选一个。
用下面的内容覆盖CentOS-Base.repo就行了。

#中科大(ustc)yum源，http://centos.ustc.edu.cn/centos/5/就是最新的，
#也可以设置成http://centos.ustc.edu.cn/centos/5.5/

[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

#第一部分结束

#============分割线============ 注意，上下两部分只选一个

#中科大(ustc)yum源，http://ftp.sjtu.edu.cn/centos/5/就是最新的，
#也可以设置成http://ftp.sjtu.edu.cn/centos/5.5/

[base]
name=CentOS-5 - Base
baseurl=http://ftp.sjtu.edu.cn/centos/5/os/$basearch/
gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-centos5

#released updates
[update]
name=CentOS-5 - Updates
baseurl=http://ftp.sjtu.edu.cn/centos/5/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
baseurl=http://ftp.sjtu.edu.cn/centos/5/addons/$basearch/
gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-centos5

#additional packages that may be useful
[extras]
name=CentOS-5 - Extras
baseurl=http://ftp.sjtu.edu.cn/centos/5/extras/$basearch/
gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-centos5

#additional packages that extend functionality of existing packages
[centosplus]
name=CentOS-5 - Plus
baseurl=http://ftp.sjtu.edu.cn/centos/5/centosplus/$basearch/
gpgcheck=1
enabled=0
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-centos5

#contrib - packages by Centos Users
[contrib]
name=CentOS-5 - Contrib
baseurl=http://ftp.sjtu.edu.cn/centos/5/contrib/$basearch/
gpgcheck=1
enabled=0
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-centos5

#第二部分结束

第2步

中科大(ustc)yum源
32位: rpm --import http://centos.ustc.edu.cn/centos/5/os/i386/RPM-GPG-KEY-CentOS-5
64位: rpm --import http://centos.ustc.edu.cn/centos/5/os/x86_64/RPM-GPG-KEY-CentOS-5

上海交大(sjtu)yum源
32位: rpm --import http://ftp.sjtu.edu.cn/centos/5/os/i386/RPM-GPG-KEY-CentOS-5
64位: rpm --import http://ftp.sjtu.edu.cn/centos/5/os/x86_64/RPM-GPG-KEY-CentOS-5

第3步

yum update