[HOWTO] set a disk identifier of your disk

[Rava]

You have to be user root. This HOWTO assumes you have a root terminal opened already.

TL;DR:
According to the man pages, only sfdisk can do so (not gparted, nor cfdisk nor fdisk)
DEVICE is the device or your drive. Cave! All partitions of that disk drive should be umounted (and swapoff'd) during this operation. Valid DEVICE is e.g. /mnt/sdb not /mnt/sdb1 !

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sfdisk --disk-id DEVICE

shows you the current disk identifier ID (helpful to not overwrite the disk identifier of the wrong device)

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sfdisk --disk-id DEVICE ID

sets the ID. It should be an appropriate randomized hex code.
Like so:

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sfdisk --disk-id /dev/sdd 0x7be907a5

The long read:
I checked two of my similar blue HAMA 8 GB USB thumbdrives.

One has the "Disk identifier" set

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root@rava:/# fdisk -l /dev/sdc
Disk /dev/sdc: 7.47 GiB, 8016363520 bytes, 15656960 sectors
Disk model: USB Flash Disk  
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: 0x7ae803a4

Device     Boot Start      End  Sectors  Size Id Type
/dev/sdc1  *       32 15656959 15656928  7.5G  b W95 FAT32

the other not:

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root@rava:/# fdisk -l /dev/sdd
Disk /dev/sdd: 7.47 GiB, 8016363520 bytes, 15656960 sectors
Disk model: USB Flash Disk  
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: 0x00000000

Device     Boot Start      End  Sectors  Size Id Type
/dev/sdd1          32 15656959 15656928  7.5G  b W95 FAT32

I looked through man fdisk but no hit for "identifier", also no hit in man cfdisk or man gparted.

Then I manually searched all appropriate man pages :

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guest@rava:/usr/man/man8$ ls -l *fdisk* gparted*
-rw-r--r-- 1 root root  8218 2022-02-15 19:37 cfdisk.8
-rw-r--r-- 1 root root 17217 2022-02-15 19:37 fdisk.8
-rw-r--r-- 1 root root  2408 2021-07-20 20:44 gparted.8
-rw-r--r-- 1 root root 26620 2022-02-15 19:37 sfdisk.8

(Of course you can only do so when you [downloaded and] activated 06-man.xzm)

And as you can see, at least according to the man pages only sfdisk can do so:
not gparted, nor cfdisk nor fdisk:

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guest@rava:/usr/man/man8$ grep -i identifier *fdisk* gparted*
sfdisk.8:Change the disk identifier. If \fIid\fP is not specified, then print the 
current identifier. The identifier is UUID for GPT or unsigned integer for MBR.
sfdisk.8:Specify the partition table identifier. It should be a hexadecimal number 
(with a 0x prefix) for MBR and a UUID for GPT.

I even searched for grep -i ident *fdisk* gparted* but there is no appropriate additional hit (I did this very search for this abbreviated search pattern because it could be on a line break with a colon in between the wrapped parts)

Let's copy the relevant [ code ] directly from man sfdisk to get rid of the inserted code for bold or underlined highlighting you get when just grep'ing the man page via the terminal:

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--disk-id device [id]
    Change the disk identifier. If id is not specified, then print the
    current identifier. The identifier is UUID for GPT or unsigned
    integer for MBR.

Since it is also the UUID a drive should not have 0x00000000 for its disk identifier.

To get the disk identifier for drive /dev/sdc:

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sfdisk --disk-id /dev/sdc

Mount the partition

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root@rava:~# mount /mnt/sdc1/

to see if it is the correct drive, e.g. via ls /mnt/sdc1/

1. umount all partitions of /mnt/sdc (there is only one partition: /mnt/sdc1/ ) and swapoff all swap partitions that could be on /mnt/sdc (there is no swap partition on /mnt/sdc; using a USB2 thumbdrive for swap would be quite silly)
2. list the current disk identifier
3. set the new disk identifier to "0x7be907a5"
4. list the current disk identifier

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root@rava:~# umount /mnt/sdc1/
root@rava:~# sfdisk --disk-id /dev/sdc
0x00000000
root@rava:~# sfdisk --disk-id /dev/sdc 0x7be907a5
Disk identifier changed from 0x00000000 to 0x7be907a5.

The partition table has been altered.
Calling ioctl() to re-read partition table.
Syncing disks.
root@rava:~# sfdisk --disk-id /dev/sdc
0x7be907a5

That's all folks!

[donald]

....only sfdisk can do so (not gparted, nor cfdisk nor fdisk)

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root@porteus:/home/guest# fdisk -l /dev/sdc
Disk /dev/sdc: 3.8 GiB, 4009754624 bytes, 7831552 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: 0xfa5d0ab8

Device     Boot Start     End Sectors  Size Id Type
/dev/sdc1        2048 7831551 7829504  3.8G 83 Linux

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root@porteus:/home/guest# fdisk /dev/sdc

Welcome to fdisk (util-linux 2.27.1).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.


Command (m for help): x

Expert command (m for help): i

Enter the new disk identifier: 0x00000000

Disk identifier changed from 0xfa5d0ab8 to 0x00000000.

Expert command (m for help): r

Command (m for help): w
The partition table has been altered.
Calling ioctl() to re-read partition table.
Syncing disks.

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root@porteus:/home/guest# fdisk -l /dev/sdc
Disk /dev/sdc: 3.8 GiB, 4009754624 bytes, 7831552 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: 0x00000000

Device     Boot Start     End Sectors  Size Id Type
/dev/sdc1        2048 7831551 7829504  3.8G 83 Linux
root@porteus:/home/guest#

[Rava]

^ Then why is

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man fdisk

not mentioning "disk identifier"?

Also, my quote said this

According to the man pages, only sfdisk can do so (not gparted, nor cfdisk nor fdisk)

(highlighting by me)