直接使用yum install命令安装时提示如下内容：

Loaded plugins: fastestmirror

There are no enabled repos.

 Run "yum repolist all" to see the repos you have.

 You can enable repos with yum-config-manager --enable <repo>

加上参数执行即可，例：

yum install iotop --releasever=7 --enablerepo=base,extras