1.进入yum文件夹

cd /etc/yum.repos.d/

2.下载阿里云源

wget "http://mirrors.aliyun.com/repo/Centos-7.repo"

3.备份系统原来的repo文件

mv CentOS-Base.repo CentOS-Base.repo.bak

4.修改Centos-7.repo名称改为CentOS-Base.repo

mv Centos-7.repo CentOS-Base.repo

5.执行yum源的更新命令

yum clean all

yum makecache

yum update