使用yum安裝計劃任務功能出錯，如下：
Another app is currently holding the yum lock; waiting for it to exit...
The other application is: PackageKit
Memory : 245 M RSS (1.1 GB VSZ)
Started: Fri Aug 16 03:10:51 2019 - 23:53 ago
State : Sleeping, pid: 11712
強制關掉yum進程：
#rm -f /var/run/yum.pid