执行yum命令时，提示
“Another app is currently holding the yum lock; waiting for it to exit…”
等错误字样。这是因为yum被锁定无法使用导致的。 错误信息参考：
Another app is currently holding the yum lock; waiting for it to exit… The other application is: yum Memory : 40 M RSS ( 50 MB VSZ) Started: Thu Jul 19 01:59:25 2012 - 03:45 ago State : Uninteruptable, pid: 903
解决方案：
rm
-rf /
var/run/yum
.pid
SSH执行以上命令，删除yum.pid强行解除锁定即可。
