备份原有repo文件

#创建一个备份目录
mkdir /etc/yum.repos.d/backup
#把所有的repo文件都移动到backup目录
mv /etc/yum.repos.d/*.repo /etc/yum.repos.d/backup

下载阿里云YUM源

#下载阿里云的yum源配置文件到/etc/yum.repos.d/CentOS-Base.repo
wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-8.repo

修改yum源文件

#查询目录结构
vim /etc/yum.repos.d/CentOS-Base.repo

#命令行模式下
%s/mirrors.cloud.aliyuncs.com/mirrors.aliyun.com/g

#再次进入命令模式
%s/$releasever/$releasever-stream/g

更新yum源配置

#清理一下
yum clean all
#生成缓存
yum makecache

#运行结果
[root@idevops ~]# yum makecache
CentOS-8-stream - Base - mirrors.aliyun.com                                                            16 MB/s |  41 MB     00:02    
CentOS-8-stream - Extras - mirrors.aliyun.com                                                          72 kB/s |  18 kB     00:00    
CentOS-8-stream - AppStream - mirrors.aliyun.com                                                       14 MB/s |  31 MB     00:02    
Metadata cache created.