[root@localhost ~]# umount 設備文件名或掛載點

[root@localhost ~]# umount /mnt/usb
#卸載U盤
[root@localhost ~]# umount /mnt/cdrom
#卸載光盤
[root@localhost ~]# umount /dev/sr0
#命令加設備文件名同樣是可以卸載的

[root@localhost ~]# mount /dev/sr0 /mnt/cdrom/

[root@localhost ~]# cd /mnt/cdrom/
#進入光盤掛載點
[root@localhost cdrom]# umount /mnt/cdrom/
umount: /mnt/cdrom: device is busy.
#報錯，設備正忙