cd /etc/yum.repos.d/
mkdir backup
mv *.repo backup/

touch Aliyun-Centos-Stream-8.repo

vi Aliyun-Centos-Stream-8.repo

[BaseOS]
name=BaseOS
baseurl=https://mirrors.aliyun.com/centos/8-stream/BaseOS/x86_64/os/
enabled=1
gpgcheck=0

[Appstream]
name=Appstream
baseurl=https://mirrors.aliyun.com/centos/8-stream/AppStream/x86_64/os/
enabled=1
gpgcheck=0

[Extras]
name=Extras
baseurl=https://mirrors.aliyun.com/centos/8-stream/extras/x86_64/os/
enabled=1
gpgcheck=0

[PowerTools]
name=PowerTools
baseurl=https://mirrors.aliyun.com/centos/8-stream/PowerTools/x86_64/os/
enabled=1
gpgcheck=0

yum clean all

yum makecache