在终端执行yum -y install wget时，终端提示：
已加载插件：fastestmirror
Loading mirror speeds from cached hostfile
There are no enabled repos.
Run "yum repolist all" to see the repos you have.
To enable Red Hat Subscription Management repositories:
subscription-manager repos --enable <repo>
To enable custom repositories:
yum-config-manager --enable <repo>
解决方法：在终端运行curl -o /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo
再运行安装命令：yum -y install wget即可
