[root@tomcat ~]# yum repolist
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 - 06:17 ago
    State  : Sleeping, pid: 14997
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: 14997

可能是系統自動升級正在運行，yum在鎖定狀態中。
已經有一個yum進程在運行了，使用kill幹掉它：

# kill -s 9 14997
# ps aux|grep yum
root 6744  0.0  0.0 103260 900 pts/1  S+  14:59  0:00 grep yum
root 14997 0.0  0.0 0    0  ?    Z  Sep19  0:01 [yumBackend.py] <defunct>1234

很遺憾，kill對付不了它，那怎麽辦呢？

可以通過強制關掉yum進程：

解決方法：
rm -rf /var/run/yum.pid 來強行解除鎖定，然後你的yum就可以運行了

yum提示Another app is currently holding the yum lock