1、yum update 、yum clean、yum install操作提示
Loaded plugins: fastestmirror, langpacks Loading mirror speeds from cached hostfile There are no enabled repos.

解决方案：

1、备份
mv /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.backup
2、
wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo
3、
yum makecache