# cat /etc/redhat-release
# cd /etc/yum.repos.d
# vim CentOS-AppStream.repo
baseurl=https://mirrors.aliyun.com/centos/$releasever/AppStream/$basearch/os/
# vim CentOS-Base.repo
baseurl=https://mirrors.aliyun.com/centos/$releasever/BaseOS/$basearch/os/
# vim CentOS-Extras.repo
baseurl=https://mirrors.aliyun.com/centos/$releasever/extras/$basearch/os/
# dnf -y install epel-release
# dnf clean all
# dnf makecache
# dnf repolist