linux挂载U盘：/dev/sda和/dev/sda1

fdisk -l
root@localhost:~# fdisk -l
Disk /dev/ram0: 4 MiB, 4194304 bytes, 8192 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes

Disk /dev/mmcblk1: 7.3 GiB, 7818182656 bytes, 15269888 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: 85260000-0000-475E-8000-7EFB00000CDA

Device Start End Sectors Size Type
/dev/mmcblk1p1 16384 24575 8192 4M unknown
/dev/mmcblk1p2 24576 32767 8192 4M unknown
/dev/mmcblk1p3 32768 40959 8192 4M unknown
/dev/mmcblk1p4 40960 106495 65536 32M unknown
/dev/mmcblk1p5 106496 172031 65536 32M unknown
/dev/mmcblk1p6 172032 237567 65536 32M unknown
/dev/mmcblk1p7 237568 368639 131072 64M unknown
/dev/mmcblk1p8 368640 12951551 12582912 6G unknown
/dev/mmcblk1p9 12951552 15269854 2318303 1.1G unknown

Disk /dev/mmcblk1boot1: 4 MiB, 4194304 bytes, 8192 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes

Disk /dev/mmcblk1boot0: 4 MiB, 4194304 bytes, 8192 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes

Disk dev/sda: 57.3 GiB, 61530439680 bytes, 120176640 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x306b2a46

Device Boot Start End Sectors Size Id Type
/dev/sda1 32 120176639 120176608 57.3G 7 HPFS/NTFS/exFAT
root@localhost:~#

在windows的cmd下通过指令，清除分区后，不能挂载：

Disk /dev/sda: 57.3 GiB, 61530439680 bytes, 120176640 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x8a1b5ae2
root@localhost:~#
root@localhost:~#
root@localhost:~#
root@localhost:~# cd /mnt
root@localhost:/mnt# ls
usb usb0
root@localhost:/mnt# mount /dev/sda /mnt/usb
NTFS signature is missing.
Failed to mount ‘/dev/sda’: Invalid argument
The device ‘/dev/sda’ doesn’t seem to have a valid NTFS.
Maybe the wrong device is used? Or the whole disk instead of a
partition (e.g. /dev/sda, not /dev/sda1)? Or the other way around?
root@localhost:/mnt#

结论：U盘只有分区了才能格式化，而在linux中挂载使用的时候看到的就是这个分区。【有了分区才有地址，然后读写使用】
https://zhidao.baidu.com/question/1673915496050147467.html