查看centos版本
cat /etc/centos-relese
备份所有
cd /etc/yum.repos.d/
mkdir repobak
mv /etc/yum.repos.d/*.repo /etc/yum.repos.d/repobak
手动安装相关 rpm
rpm -Uvh --force http://mirror.centos.org/centos-7/7.9.2009/os/x86_64/Packages/centos-release-7-9.2009.0.el7.centos.x86_64.rpm
< 也可以使用清华源 https://mirrors.tuna.tsinghua.edu.cn/centos/7.9.2009/os/x86_64/Packages/centos-release-7-9.2009.0.el7.centos.x86_64.rpm
重新缓存
yum clean all
yum makecache