1、将 CentOS-Base.repo 备份为CentOS-Base.repo.backup 防止丢失

cp /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.backup

2、下载阿里云CentOS-Base.repo文件

从https://mirrors.aliyun.com/repo/Centos-8.repo,并命名为CentOS-Base.repo

curl -o /etc/yum.repos.d/CentOS-Base.repo https://mirrors.aliyun.com/repo/Centos-8.repo

或者

wget -O /etc/yum.repos.d/CentOS-Base.repo https://mirrors.aliyun.com/repo/Centos-8.repo

3、清除缓存

清除系统所有的yum缓存

yum clean all

生成yum缓存

yum makecache

如果需要更新现有包，可使用下面命令

yum upgrade