1 卸载
sudo umount /home/pi/NAS/NAS1
sudo udisksctl unmount --block-device /dev/sdb1
2 关闭电源，如果是USB移动硬盘可以听到硬盘停转了。
udisksctl power-off -b /dev/sdb
3 lsblk 检查发现卸载的干干净净
pi@pi:~/Scripts $ lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda 8:0 1 29.3G 0 disk
├─sda1 8:1 1 28.1G 0 part /home/pi/NAS/NAS0
└─sda2 8:2 1 447.1M 0 part
mmcblk0 179:0 0 14.5G 0 disk
├─mmcblk0p1 179:1 0 256M 0 part /boot
└─mmcblk0p2 179:2 0 14.2G 0 part /
