备份原镜像
mv /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.backup
下载阿里云镜像
下载新的 CentOS-8.repo 到 /etc/yum.repos.d/
wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-8.repo
或者
curl -o /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-8.repo
删除不能登陆的http://mirrors.aliyuncs.com和http://mirrors.cloud.aliyuncs.com
sed -i -e '/mirrors.cloud.aliyuncs.com/d' -e '/mirrors.aliyuncs.com/d' /etc/yum.repos.d/CentOS-Base.repo
生成缓存生效
运行 yum makecache