umount不掉挂载点时的处理方法

[root@oradoc ~]# mount /dev/cdrom /dev/mnt
mount: /dev/sr0 is write-protected,mounting read-only
[root@oradoc ~]# df -h
Filesystem           Size  Used Avail Use% Mounted on
devtmpfs             3.8G     0  3.8G   0% /dev
tmpfs                3.8G     0  3.8G   0% /dev/shm
tmpfs                3.8G  8.4M  3.8G   1% /run
tmpfs                3.8G     0  3.8G   0% /sys/fs/cgroup
/dev/mapper/ol-root   84G   23G   62G  27% /
/dev/sda1            197M  151M   47M  77% /boot
tmpfs                773M     0  773M   0% /run/user/0
/dev/sr0             4.4G  4.4G     0 100% /dev/mnt
[root@oradoc ~]# cd /dev/mnt
[root@oradoc mnt]# ls -lrt
total 1050
drwxr-xr-x. 5 root root   2048 Nov  8  2016 addons
-rw-r--r--. 1 root root   1011 Nov  8  2016 RPM-GPG-KEY-oracle
-rw-r--r--. 1 root root   1011 Nov  8  2016 RPM-GPG-KEY
-rw-r--r--. 1 root root 187067 Nov  8  2016 RELEASE-NOTES-U3-en.html
-rw-r--r--. 1 root root  64277 Nov  8  2016 RELEASE-NOTES-U3-en
-rw-r--r--. 1 root root  18390 Nov  8  2016 GPL
-rw-r--r--. 1 root root   8643 Nov  8  2016 EULA
drwxr-xr-x. 2 root root 776192 Nov  8  2016 Packages
drwxr-xr-x. 2 root root   4096 Nov  8  2016 repodata
drwxr-xr-x. 2 root root   2048 Nov  8  2016 LiveOS
drwxr-xr-x. 3 root root   2048 Nov  8  2016 EFI
drwxr-xr-x. 3 root root   2048 Nov  8  2016 images
-r--r--r--. 1 root root   3322 Nov  8  2016 TRANS.TBL
drwxr-xr-x. 2 root root   2048 Nov  8  2016 isolinux
[root@oradoc mnt]# umount /dev/mnt
umount: /dev/mnt: target is busy.
        (In some cases useful info about processes that use
         the device is found by lsof(8) or fuser(1))
[root@oradoc mnt]# fuser -m  /dev/mnt
-bash: fuser: command not found
[root@oradoc mnt]# yum install fuser
Loaded plugins: ulninfo
No package fuser available.
Error: Nothing to do
[root@oradoc mnt]# yum provides fuser
Loaded plugins: ulninfo
ol7_addons/x86_64/filelists                                                                                                           | 334 kB  00:00:00     
psmisc-22.20-8.el7.x86_64 : Utilities for managing processes on your system
Repo        : ol7_latest
Matched from:
Filename    : /usr/sbin/fuser



psmisc-22.20-9.el7.x86_64 : Utilities for managing processes on your system
Repo        : ol7_latest
Matched from:
Filename    : /usr/sbin/fuser



psmisc-22.20-11.el7.x86_64 : Utilities for managing processes on your system
Repo        : ol7_latest
Matched from:
Filename    : /usr/sbin/fuser



psmisc-22.20-15.el7.x86_64 : Utilities for managing processes on your system
Repo        : ol7_latest
Matched from:
Filename    : /usr/sbin/fuser



[root@oradoc mnt]# yum install psmisc
Loaded plugins: ulninfo
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                             ol7_latest                             140 k

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

Total download size: 140 k
Installed size: 475 k
Is this ok [y/d/N]: y
Downloading packages:
psmisc-22.20-15.el7.x86_64.rpm                                                                                                        | 140 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!
[root@oradoc mnt]# fuser -m  /dev/mnt
/dev/mnt:             2398c
[root@oradoc mnt]# ps -ef | grep 2398
root      2398  2394  0 07:46 pts/0    00:00:00 -bash
root      2438  2398  0 07:49 pts/0    00:00:00 ps -ef
root      2439  2398  0 07:49 pts/0    00:00:00 grep --color=auto 2398
[root@oradoc mnt]#

后面 c 代表的意思可参考下述:

* c: current directory. * e: executable being run. * f: open file. f is omitted in default display mode. * F: open file for writing. F is omitted in default display mode. * r: root directory. * m: mmap'ed file or shared library.