#1.備份
mv /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.backup

#2.下載新的CentOS-Base.repo 到/etc/yum.repos.d/
wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo
或者
curl -o /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo

#3.運(yùn)行 yum makecache

#4.運(yùn)行yum install epel-release

#5.運(yùn)行yum install nginx