备份当前 yum 源配置

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cd /etc/yum.repos.d/
rename repo repo.old CentOS-*.repo

重建官方yum源

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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

替换阿里云源

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wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo

重建缓存

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yum clean all
yum makecache

提醒

建议全程使用root进行操作