cd /etc/yum.repos.d/
mkdir backup
mv CentOS-* backup/
wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo
yum clean all
yum install -y epel-release
yum clean all
yum makecache
yum repolist enabled
yum repolist all
原文：https://www.cnblogs.com/lmgsanm/p/10726648.html