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 https://mirrors.aliyun.com/repo/Centos-7.repo

3.重新生成緩存

yum makecache