RedHat Enterprise因为是商业软件，所以没有注册就不能更新或用yum方便的安装软件。想到Ubuntu使用/etc/apt/sources.list文件进行1、修改.repo文件
cd /etc/yum.repos.d/
vim CentOS-Base.repo更新，而CentOs是RHEL的翻版，就直接用CentOS的更新源来更新吧。
写入以下内容：
[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/os/$basearch/
gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-centos5
#released updates
[update]
name=CentOS-5 – Updates
#mirrorlist=http://mirrorlist.centos.org/?release=4&arch=$basearch&repo=updates
baseurl=http://ftp.sjtu.edu.cn/centos/5/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/addons/$basearch/
gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-centos5
#additional packages that may be useful
[extras]
name=CentOS-5 – Extras
#mirrorlist=http://mirrorlist.centos.org/?release=4&arch=$basearch&repo=extras
baseurl=http://ftp.sjtu.edu.cn/centos/5/extras/$basearch/
gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-centos5
#additional packages that extend functionality of existing packages
[centosplus]
name=CentOS-5 – Plus
#mirrorlist=http://mirrorlist.centos.org/?release=4&arch=$basearch&repo=centosplus
baseurl=http://ftp.sjtu.edu.cn/centos/5/centosplus/$basearch/
gpgcheck=1
enabled=0
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-centos5
#contrib – packages by Centos Users
[contrib]
name=CentOS-5 – Contrib
#mirrorlist=http://mirrorlist.centos.org/?release=4&arch=$basearch&repo=contrib
baseurl=http://ftp.sjtu.edu.cn/centos/5/contrib/$basearch/
gpgcheck=1
enabled=0
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-centos5
创建或者更改 vi dag.repo
写入：
[dag]
name=Dag RPM Repository for RHEL5
baseurl=http://ftp.riken.jp/Linux/dag/redhat/el5/en/$basearch/dag/
enabled=1
gpgcheck=1
gpgkey=http://ftp.riken.jp/Linux/dag/packages/RPM-GPG-KEY.dag.txt
导入KEY：
rpm –import
使用 yum update 更新测试！