參考文獻：
https://www.cnblogs.com/itxdm/p/restore_yum.html
yum報錯error: rpmdb open failed
這種情況一般是由於rpm數據庫被損壞導致的，可按照下述方法重建yum數據庫：
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cd /var/lib/rpm/
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rm -rf __db.*
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rpm –rebuilddb
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yum clean all
yum 重建 用於無法恢復情況下：
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cat /etc/issus
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rpm -qa |grep release
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arch
rpm -Uvh http://mirror.centos.org/centos/6/os/x86_64/Packages/centos-release-6-8.el6.centos.12.3.x86_64.rpm
rpm -Uvh http://repo.webtatic.com/yum/el6/latest.rpm
rpm -ivh http://rpms.famillecollet.com/enterprise/remi-release-6.rpm
rpm -Uvh http://pkgs.repoforge.org/rpmforge-release/rpmforge-release-0.5.3-1.el7.rf.x86_64.rpm