若有其他用户正在访问某个挂载点，则无法卸载该挂载点
[root@station110 ~]# umount /dev/sda6
umount: /media/book: device is busy.
(In some cases useful info about processes that use
the device is found by lsof(8) or fuser(1))
查看是谁正在访问此挂载点
the device is found by lsof(8) or fuser(1))
[root@station110 ~]# fuser /media/book
/media/book: 3100c
fuser -km [MOUNT_POINT]: 强行杀死正在访问此挂载点的进程；
root@station110 ~]# fuser -km /media/book
/media/book: 3100c
查看内核识别的分区信息：
cat /proc/partitions
major minor #blocks name
8 0 125829120 sda
8 1 204800 sda1
8 2 62914560 sda2
8 4 1 sda4
8 5 52435129 sda5
8 6 10273536 sda6
8 16 20971520 sdb
253 0 20971520 dm-0
253 1 2097152 dm-1
253 2 10485760 dm-2
253 3 20971520 dm-3