Error set: /var/run/yum.pid is locked when yum is installed, and another program with PID 2828 is running.

Error: /var/run/yum.pid was locked when yum was installed in the ELK experiment and another program with PID 2828 was running.

1. Error reporting phenomenon:

[root@apache ~]#yum -y install httpd
已加载插件：fastestmirror, langpacks
/var/run/yum.pid 已被锁定，PID 为 2828 的另一个程序正在运行。
Another app is currently holding the yum lock; waiting for it to exit...
  另一个应用程序是：PackageKit
    内存： 48 M RSS （463 MB VSZ）
    已启动： Mon Mar 15 12:59:55 2021 - 3:20:17之前
    状态  ：睡眠中，进程ID：2828
Another app is currently holding the yum lock; waiting for it to exit...
  另一个应用程序是：PackageKit
    内存： 48 M RSS （463 MB VSZ）
    已启动： Mon Mar 15 12:59:55 2021 - 3:20:19之前
    状态  ：睡眠中，进程ID：2828
Another app is currently holding the yum lock; waiting for it to exit...
  另一个应用程序是：PackageKit
    内存： 48 M RSS （463 MB VSZ）
    已启动： Mon Mar 15 12:59:55 2021 - 3:20:21之前
    状态  ：睡眠中，进程ID：2828
^C

Exiting on user cancel.

2. Solution:

The reason is: the yum command can only download one software at a time, so when you need to download the second software package, the system will lock yum with the process lock; sometimes when you use yum to upgrade some files, this is the case.
After deleting its process file, run yum again to be available.

rm -rf /var/run/yum.pid