今天在日常进行CentOS操作的时候，不知为何yum -y install xxx命令突然卡死不动，Ctrl+C取消执行也无解，遂关闭SSH重新建立连接，然而再次重新执行yum -y install xxx命令时却报如下错误：
...
root@localhost:~>yum -y install xxx
Loaded plugins: fastestmirror, langpacks
Existing lock /var/run/yum.pid: another copy is running as pid 27970.
Another app is currently holding the yum lock; waiting for it to exit...
The other application is: yum
Memory : 43 M RSS (362 MB VSZ)
Started: Mon Jul 13 18:27:38 2020 - 03:46 ago
State : Uninterruptible, pid: 27970
Another app is currently holding the yum lock; waiting for it to exit...
The other application is: yum
Memory : 43 M RSS (362 MB VSZ)
Started: Mon Jul 13 18:27:38 2020 - 03:48 ago
State : Uninterruptible, pid: 27970
...
初步判断应该是进程号为27970的那个假死了，即使刚才SSH关闭了也并没有杀掉他，遂干脆利落的执行了kill -9 27970直接杀死，后再执行yum -y install xxx命令，结果又有报错：
...
root@localhost:~>yum -y install xxx
error: rpmdb: BDB0113 Thread/process 27970/140274709284672 failed: BDB1507 Thread died in Berkeley DB library
error: db5 error(-30973) from dbenv->failchk: BDB0087 DB_RUNRECOVERY: Fatal error, run database recovery
error: cannot open Packages index using db5 - (-30973)
error: cannot open Packages database in /var/lib/rpm
CRITICAL:yum.main:
Error: rpmdb open failed
...
哦豁，凉了，rpmdb本地数据存储文件炸了……不过好在有解决方法。
执行如下命令，清理YUM仓库本地数据存储文件：
mv /var/lib/rpm/__db* /tmp;
执行如下命令，清理yum缓存：
rpm --rebuilddb;
yum clean all
大功告成。
现在细想一下，yum当时有可能是因为网络问题假死，可能再等等就好了，不过毕竟当时有点着急，以后得注意下。