CentOS 7.5 最小化安装之后突遇停电，导致系统无法正常启动直接进入修复模式，经过文件系统修复之后系统开机启动。

进系统之后，启动某些服务发现仍然有分区文件损坏，于是想要卸载分区挂载点来修复文件系统，结果执行umount的时候无法卸载，逐执行fuser命令查看是什么进程在占用，结果直接报-bash: fuser: command not found，找不到此命令。

一般这种错误就是系统没有安装相关的包，所以没有这个命令，解决方法很简单，找到这个命令在哪个包里，安装上就可以了，但是麻烦的就是很多命令你不知道是在哪个包里面，还好yum有个功能可以查到某个命令在哪个包里面，使用yum provides  ifconfig，yum provides lsof，yum provides fuser等可以查到这个命令的安装包是什么，用起来很方便。

# yum provides fuser
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
 * base: mirrors.aliyun.com
 * extras: mirrors.aliyun.com
 * updates: mirrors.aliyun.com
psmisc-22.20-15.el7.x86_64 : Utilities for managing processes on your system
Repo        : base
Matched from:
Filename    : /usr/sbin/fuser

psmisc-22.20-15.el7.x86_64 : Utilities for managing processes on your system
Repo        : @base
Matched from:
Filename    : /usr/sbin/fuser

知道在哪个包里使用yum安装即可。

# yum -y install psmisc
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
 * base: mirrors.aliyun.com
 * extras: mirrors.aliyun.com
 * updates: mirrors.aliyun.com
base                                                                                                                              | 3.6 kB  00:00:00     
extras                                                                                                                            | 3.4 kB  00:00:00     
updates                                                                                                                           | 3.4 kB  00:00:00     
Resolving Dependencies
--> Running transaction check
---> Package psmisc.x86_64 0:22.20-15.el7 will be installed
--> Finished Dependency Resolution

Dependencies Resolved

=========================================================================================================================================================
 Package                            Arch                               Version                                    Repository                        Size
=========================================================================================================================================================
Installing:
 psmisc                             x86_64                             22.20-15.el7                               base                             141 k

Transaction Summary
=========================================================================================================================================================
Install  1 Package

Total download size: 141 k
Installed size: 475 k
Downloading packages:
psmisc-22.20-15.el7.x86_64.rpm                                                                                                    | 141 kB  00:00:00     
Running transaction check
Running transaction test
Transaction test succeeded
Running transaction
  Installing : psmisc-22.20-15.el7.x86_64                                                                                                            1/1 
  Verifying  : psmisc-22.20-15.el7.x86_64                                                                                                            1/1 

Installed:
  psmisc.x86_64 0:22.20-15.el7                                                                                                                           

Complete!