Another app is currently holding the yum lock; waiting for it to exit…
The other application is: PackageKit
Memory : 153 M RSS (266 MB VSZ)
Started: Thu Jul 12 00:03:05 2012 – 06:19 ago
State : Sleeping, pid: 4018
解决方法：
rm -rf /var/run/yum.pid 来强行解除锁定，然后yum就可以运行了
