MacOS – How to change an NTFS Volume UUID

disk-volumemacosntfspartitionuuid

I just upgraded my Mac to Mac OS X El Capitan and I wanted to update my Windows 7 to Windows 10.
But, before that, I need to make a backup of my Windows partition.

As I've done it before, I have a Windows (NTFS) partition on a backup HDD.

The thing is, I want to make a new backup with Carbon Copy Cloner, but it tell's me it can't be done because there are two volumes with same UUID.

OK, then, I fight with my Windows backup partition to have it a different UUID from the one I got for my "local" Windows partition… and I'm loosing the fight !

I have this when using diskutil info /dev/disk0s2 :

   Device Identifier:        disk0s2
   Device Node:              /dev/disk0s2
   Whole:                    No
   Part of Whole:            disk0
   Device / Media Name:      Windows_NTFS_Untitled_3

   Volume Name:              Win

   Mounted:                  Yes
   Mount Point:              /Volumes/Win

   File System Personality:  NTFS
   Type (Bundle):            ntfs
   Name (User Visible):      Windows NT File System (NTFS)

   Partition Type:           Microsoft Basic Data
   OS Can Be Installed:      No
   Media Type:               Generic
   Protocol:                 SATA
   SMART Status:             Verified
   Volume UUID:              24D65D1E-43E8-4FF0-BBBF-A82CC6B45D20
   Disk / Partition UUID:    D5C23E74-E658-45E1-B9B3-44681D0D02C2

   Total Size:               85.0 GB (84999667712 Bytes) (exactly 166014976 512-Byte-Units)
   Volume Free Space:        34.1 GB (34093342720 Bytes) (exactly 66588560 512-Byte-Units)
   Device Block Size:        512 Bytes
   Allocation Block Size:    4096 Bytes

   Read-Only Media:          No
   Read-Only Volume:         No

   Device Location:          Internal
   Removable Media:          No

   Solid State:              No

… and I have this using diskutil info /dev/disk1s4 :

   Device Identifier:        disk1s4
   Device Node:              /dev/disk1s4
   Whole:                    No
   Part of Whole:            disk1
   Device / Media Name:      WindowsB

   Volume Name:              Windows

   Mounted:                  Yes
   Mount Point:              /Volumes/Windows

   File System Personality:  NTFS
   Type (Bundle):            ntfs
   Name (User Visible):      Windows NT File System (NTFS)

   Partition Type:           Microsoft Basic Data
   OS Can Be Installed:      No
   Media Type:               Generic
   Protocol:                 USB
   SMART Status:             Not Supported
   Volume UUID:              24D65D1E-43E8-4FF0-BBBF-A82CC6B45D20
   Disk / Partition UUID:    C8E2A2D5-6065-4903-8BB6-AC02698323A6

   Total Size:               84.7 GB (84655734784 Bytes) (exactly 165343232 512-Byte-Units)
   Volume Free Space:        44.0 GB (44012474368 Bytes) (exactly 85961864 512-Byte-Units)
   Device Block Size:        512 Bytes
   Allocation Block Size:    4096 Bytes

   Read-Only Media:          No
   Read-Only Volume:         No

   Device Location:          External
   Removable Media:          No

As you can see, the "Disk / Partition UUID" is different, but not the "Volume UUID".

Does anybody have a solution to change the "Volume UUID"?

Best Answer

Usually NTFS volumes don't contain UUIDs. The visible UUID in diskutil is derived from the NTFS Volume Serial Number.

Get the disk identifier of your backup disk and the volume:

diskutil list

Unmount the external disk:

diskutil umountDisk /dev/disk1

Copy the NTFS superblock:

sudo dd if=/dev/disk1s4 of=~/Desktop/superblock bs=512 count=1

Change the mod bits:

sudo chmod 777 ~/Desktop/superblock

Create a backup of the superblock (just in case!):

cp ~/Desktop/superblock ~/Desktop/superblock.backup

Modify the file superblock with HexFiend:

Hexfiend superblock

The NTFS volume serial number is highlighted in violet (eight bytes beginning at offset 72 or 0x48). Modify at least one byte. After saving the file check the size which should still be 512 Bytes.

Write back the superblock:

sudo dd if=~/Desktop/superblock of=/dev/disk1s4 bs=512 count=1

Reboot your Mac and verify the new UUID of disk1s4.

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