今天很是郁闷，带着EMOS的光盘结果坏了，安装Centos 又不成功，换了N次 都是一样，没办法，只好换redhat 来试下，结果OK ，就安装rhel，但是rhel 升级不好升级，我就决定把rhel  升级为Centos
1.安装安全证书
2.安装release package
rpm -Uvh http://mirror.centos.org/centos-5/5.4/os/i386/CentOS/centos-release-notes-5.4-4.i386.rpm
rpm -Uvh http://mirror.centos.org/centos-5/5.4/os/i386/CentOS/centos-release-5-4.el5.centos.1.i386.rpm
3.删除rhel的yum
rpm -e yum-rhn-plugin-0.4.3-1.el5
rpm -e yum-updatesd-3.0.1-5.el5
rpm -e yum-3.0.1-5.el5 --nodeps
rpm -e yum-metadata-parser-1.0-8.fc6 --nodeps
4. 安装 CentOS的yum
rpm -Uvh http://mirror.centos.org/centos-5/5.4/os/i386/CentOS/yum-fastestmirror-1.1.16-13.el5.centos.noarch.rpm  --nodeps
rpm -Uvh http://mirror.centos.org/centos-5/5.4/os/i386/CentOS/yum-3.2.22-20.el5.centos.noarch.rpm --nodeps
5.安装成功。
yum update