在CentOS下运行yum install flash-plugin或yum install mplayer的时候，提示库里没有找到这个软件？为什么会这样？因为CentOS是RHEL编译过来的，去掉了所有关于版权问题的东西。因此，在没有使 用第三方软件库的情况下，很多软件无法用yum install来直接安装。 这时候，我们就需要扩展yum库，CentOS下安装RPMforge，下载RPMforge。RPMForge库现在已经拥有超过10000种的CentOS的软件包，被CentOS社区认为是最安全也是最稳定的一个第三方软件库。

RPMFORGE 的centos官方安装文档：http://wiki.centos.org/AdditionalResources/Repositories/RPMForge

CentOS 5 下安装RPMforge

下载RPMforge

• i386 http://packages.sw.be/rpmforge-release/rpmforge-release-0.5.2-2.el5.rf.i386.rpm

• x86_64 http://packages.sw.be/rpmforge-release/rpmforge-release-0.5.2-2.el5.rf.x86_64.rpm

The preferred rpmforge-release package to retrieve and to install in order to enable that repository is one of the two listed above.

Install DAG's GPG key

rpm --import http://apt.sw.be/RPM-GPG-KEY.dag.txt

Verify the package you have downloaded

rpm -K rpmforge-release-0.5.2-2.el5.rf.*.rpm

Security warning: The rpmforge-release package imports GPG keys into your RPM database. As long as you have verified the md5sum of the key injection package, and trust Dag, et al., then it should be as safe as your trust of them extends.

安装RPMforge

rpm -i rpmforge-release-0.5.2-2.el5.rf.*.rpm