卸载目录时，当前位置不能处于要卸载的目录，否则卸载不成功
Every wonder why sometimes you get this message when you try to un-mount a NFS drive or cdrom drive （不能卸载的情形）
CODE
root@homer:~# umount /mnt/cdrom
umount: /mnt/cdrom: device is busy
umount: /mnt/cdrom: device is busy
root@homer:~#
Well chances a process is running that is using that directory. To find out run （有关的运行的进程）
CODE
root@homer:~# fuser -m /mnt/cdrom/
/mnt/cdrom/: 24066c
That shows you what process is using that directory. Now lets do a ps aux and see whats running （查看哪个进程使用了这个目录）
CODE
root@homer:~# ps aux | grep 24066
root 24066 0.0 0.5 2244 1284 pts/10 S 14:04 0:00 -su
root@homer:~#
Looks like a the root user is in that directory. If you cannot find the term that is in that directory then kill that process（杀死进程）
CODE
root@homer:~# kill -9 24066
root@homer:~#
now you can un-mount （可以卸载）
CODE
root@homer:~# umount /mnt/cdrom/
root@homer:~#
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