使用CentOS时，使用yum安装软件，老是会遇到这种提示：
Existing lock /var/run/yum.pid: another copy is running as pid 3053.
Another app is currently holding the yum lock; waiting for it to exit...
The other application is: PackageKit
Memory : 37 M RSS ( 82 MB VSZ)
Started: Sun Jan 24 16:11:53 2010 - 14:44 ago
State : Sleeping, pid: 3053
后来才发现只要把/etc/yum/pluginconf.d/refresh-packagekit.conf改为如下：
enabled=0
就OK了。