1. 备份当前yum源配置
cd /etc/yum.repos.d/
rename repo repo.old CentOS-*.repo
2. 重建官方yum源
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
3. 重建缓存
yum clean all
yum makecache