當我在安裝python包時，往往會依賴以下幾個包，但是有些電腦會出現以下錯誤：

[[email protected] scrapy-cluster-1.2]# yum install gcc libffi-devel python-devel openssl-devel
Loaded plugins: fastestmirror, refresh-packagekit, security
Existing lock /var/run/yum.pid: another copy is running as pid 4776.
Another app is currently holding the
 
 yum lock; waiting for it to exit...
  The other application is: PackageKit
    Memory :  52 M RSS (433 MB VSZ)
    Started: Tue Jun 14 11:17:51 2016 - 338 day(s) 4:56:20 ago
    State  : Sleeping, pid: 4776
Another app is currently holding the yum lock; waiting for it to exit...
  The other application
 
 is: PackageKit
    Memory :  52 M RSS (433 MB VSZ)
    Started: Tue Jun 14 11:17:51 2016 - 338 day(s) 4:56:22 ago
    State  : Sleeping, pid: 4776
Another app is currently holding the yum lock; waiting for it to exit...
  The other application is: PackageKit
    Memory :  52 M RSS (433 MB VSZ)
    Started: Tue Jun 14
 
 11:17:51 2016 - 338 day(s) 4:56:24 ago
    State  : Sleeping, pid: 4776
Another app is currently holding the yum lock; waiting for it to exit...
  The other application is: PackageKit
    Memory :  52 M RSS (433 MB VSZ)
    Started: Tue Jun 14 11:17:51 2016 - 338 day(s) 4:56:26 ago
    State  : Sleeping, pid: 4776
Another app is currently holding the yum lock; waiting for it to exit...
  The other application is: PackageKit
    Memory :  52 M RSS (433 MB VSZ)
    Started: Tue Jun 14 11:17:51 2016 - 338 day(s) 4:56:28 ago
    State  : Sleeping, pid: 4776
Another app is currently holding the yum lock; waiting for it to exit...
  The other application is: PackageKit
    Memory :  52 M RSS (433 MB VSZ)
    Started: Tue Jun 14 11:17:51 2016 - 338 day(s) 4:56:30 ago
    State  : Sleeping, pid: 4776
Another app is currently holding the yum lock; waiting for it to exit...
  The other application is: PackageKit
    Memory :  52 M RSS (433 MB VSZ)
    Started: Tue Jun 14 11:17:51 2016 - 338 day(s) 4:56:32 ago
    State  : Sleeping, pid: 4776
Another app is currently holding the yum lock; waiting for it to exit...
  The other application is: PackageKit
    Memory :  52 M RSS (433 MB VSZ)
    Started: Tue Jun 14 11:17:51 2016 - 338 day(s) 4:56:34 ago
    State  : Sleeping, pid: 4776
Another app is currently holding the yum lock; waiting for it to exit...
  The other application is: PackageKit
    Memory :  52 M RSS (433 MB VSZ)
    Started: Tue Jun 14 11:17:51 2016 - 338 day(s) 4:56:36 ago
    State  : Sleeping, pid: 4776
Another app is currently holding the yum lock; waiting for it to exit...
  The other application is: PackageKit
    Memory :  52 M RSS (433 MB VSZ)
    Started: Tue Jun 14 11:17:51 2016 - 338 day(s) 4:56:38 ago
    State  : Sleeping, pid: 4776

遇到這個錯誤我們可以用以下命令解決：

[root@pachong1 scrapy-cluster-1.2]# rm -f /var/run/yum.pid 4776

至此，你安裝這些依賴不會報這個錯誤，這個錯誤的原因是因為：
/var/run/yum.pid 已被鎖定，PID 為 4776 的另一個程式正在執行。另外一個程式鎖定了 yum。刪除yum.pid即可。

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