Set and Verify FAT Labels and Volume IDs with fatlabel

You can rename a USB stick or camera card in seconds with fatlabel, and read or set its 32-bit hexadecimal volume ID while you are there. This guide uses dosfstools 4.2, the version installed on the machine used for these examples. Allow about five minutes, including a read-back to prove it worked.

Before you start

You need the fatlabel command from the dosfstools package and the path to a FAT filesystem.

• Practise safely. A regular user can experiment on an image file they own.
• Real devices need privileges. A USB stick or disk partition normally does, so use sudo for the individual command rather than making the whole shell a root shell.
• Unmount first. Do not operate on a filesystem while it is mounted or being written to. A label change is small, but it still writes filesystem metadata.

Identify the intended device before anything else:

lsblk -f
findmnt --source /dev/sdX1

Replace /dev/sdX1 with the actual FAT device. The second command should produce no entry before you continue. If it shows a mount point, stop and unmount that filesystem during a maintenance window. The operand is a whole-disk image or a partition; a directory containing a mounted filesystem is not.

1. Read the current label

With no new value, fatlabel prints the existing label:

sudo fatlabel /dev/sdX1

For example, the output might be:

CAMERA

In label mode, which is the default, an omitted second argument means read rather than change. The historical name dosfslabel is an alias in this guide's source set, but prefer fatlabel.

2. Change a label

Pass the new label after the device. Keep it to 11 bytes or fewer. Upper-case ASCII is the safest choice when older DOS or Windows systems will read the volume:

sudo fatlabel /dev/sdX1 ARCHIVE

A successful change normally prints nothing. Read it back immediately:

sudo fatlabel /dev/sdX1

ARCHIVE

old_label=$(sudo fatlabel /dev/sdX1); echo "$old_label"

What gets rejected or goes wrong:

• Empty or whitespace labels. Do not pass them.
• Anything over 11 bytes. Rejected.
• Non-ASCII text. It depends on the DOS codepage used for encoding. The default is codepage 850.

If another system expects a different DOS codepage, select it explicitly:

sudo fatlabel --codepage=932 /dev/sdX1 CAMERA

3. Read and set the volume ID

A FAT volume also has a numeric volume ID. Select volume ID mode with --volume-id or its short form -i:

sudo fatlabel --volume-id /dev/sdX1

The output is hexadecimal, such as:

a61a0e1b

To set a known ID, supply hexadecimal digits without a leading 0x:

sudo fatlabel --volume-id /dev/sdX1 1A2B3C4D
sudo fatlabel --volume-id /dev/sdX1

1a2b3c4d

The value must fit in 32 bits. A volume ID is not a backup or an integrity check. Change it only when a tool or migration demands a particular identifier, because software may use it to recognise removable media.

4. Reset a label or ID

sudo fatlabel --reset /dev/sdX1
sudo fatlabel /dev/sdX1

The second command should print no label. To undo it, set the recorded old label again:

sudo fatlabel /dev/sdX1 ARCHIVE

In volume ID mode, reset generates a new ID rather than removing the ID:

sudo fatlabel --volume-id --reset /dev/sdX1
sudo fatlabel --volume-id /dev/sdX1

Common traps

• Wrong device. Stop if lsblk -f does not match the expected filesystem type, size and label. A device name such as /dev/sdb1 can change when removable storage is reconnected.
• Mounted or busy filesystem. Unmount it and retry. Do not force a metadata write into a filesystem that another process is using.
• Rejected label. Shorten it, remove whitespace-only input, and use upper-case ASCII unless you have checked the required codepage.
• Invalid volume ID. Remove 0x and use at most eight hexadecimal digits, for example 1A2B3C4D.
• Unexpected label on another operating system. FAT labels have historically been stored in both the boot sector and the root directory. fatlabel 4.2 reads the root-directory label and updates both locations when changing it, which is what common DOS and Windows readers expect.