比如说当我需要安装cloudstack for kvm的agent的时候，为了方便起见，我首先使用yum的方式进行安装，
“yum install cloudstack-agent”
可以执行这个命名时，任何rpm包都没有安装，并出现下面的提示信息
“
...
Error:Noting to do
”此时再看cloudstack的官方网站上提供了配置yum的方式来安装cloudstack-agent，于是根据官方网站的说明采取如下的步骤进行配置
“4.4.2. RPM package repository
There is a RPM package repository for CloudStack so you can easily install on RHEL based platforms.
If you're using an RPM-based system, you'll want to add the Yum repository so that you can install CloudStack with Yum.
Yum repository information is found under /etc/yum.repos.d. You'll see several .repo files in this directory, each one denoting a specific repository.
To add the CloudStack repository, create /etc/yum.repos.d/cloudstack.repo and insert the following information.
[cloudstack]
name=cloudstack
baseurl=http://cloudstack.apt-get.eu/rhel/4.2/
enabled=1
gpgcheck=0”
