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Recently, I have noticed that I cannot access my USB flash drive filesystem (it was of FAT type, as far as I can remember). Fedora did not mount it automatically and lsblk could not see the partition. So, I decided to create new partition (instead of wiping the device at first) with fdisk.

The process was straightforward (fdisk did not complain a bit), but I noticed that fdisk asks me as a last step about removing a thing called "vfat signature":

Created a new partition 1 of type 'Linux' and of size 7.3 GiB.
Partition #1 contains a vfat signature.

Do you want to remove the signature? [Y]es/[N]o:

I am aware that happily creating new partition in such a case may not be the best thing. I do not know yet, what I would like to/should do. However, nonetheless, primarily I am curious, so I would like to know:

  1. What is a "vfat signature"?
  2. What is the reason that fdisk detects it?
  3. What is the purpose that fdisk detects it?
  4. Is it somehow related to a term that I have encountered in the context of Windows, "disk signature"?
  5. Why would I like to remove it or not?

I have searched for a similar question here, but found only this question which does not answer my doubts.

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  • It is NOT a part of vfat / fat it is a part of the gpt partition table see thestarman.pcministry.com/asm/mbr/GPT.htm#TGPT . You can remove it if you wish to reparation, otherwise leave it alone Commented Oct 26, 2018 at 16:24
  • @Panther, thanks. That clears things a bit. So, should I read mainly about GPT? Then why is this "signature" called "vfat"? Commented Oct 26, 2018 at 16:37
  • @RuiFRibeiro, why did you remove the note at the bottom of the question? Commented Oct 26, 2018 at 16:38
  • The SE community the "tradition" of moderating questions. As per our FAQ request for materials make without doubt this question off-topic. Please see our FAQ. As for signature, it is basically a mark that signals a partition is there, and it is quite useful. Commented Oct 26, 2018 at 16:41
  • @RuiFRibeiro, thanks for clarification. I will read the FAQ. Commented Oct 26, 2018 at 16:46

2 Answers 2

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The signature partition is basically a mark/beacon there is something there, and it is not empty. It also may identify a partition.

It is useful on the context of several utilities/OS to tell the partition has already data there.

Moving a partition size/recreating a partition is usually a non-destructive operation up to the point before formatting it.

So a signature warning is signalling you "There is already data here!...are you sure you want to go ahead?"

As for removing it or not, it depends on wether you are for instance resizing a partition or creating a partition anew. If you are creating a partition anew, obviously you may want to remove the signature, if you are resizing a partition you surely want to keep it.

The use of partition signatures is not exclusive to Linux.

From How to wipe a signature from a disk device on Linux with wipefs command

Each disk and partition has some sort of signature and metadata/magic strings on it. The metadata used by operating system to configure disks or attach drivers and mount disks on your system

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  • RuiFRibeiro, thanks. As far as I know, "vfat" is a linux filesystem driver for the FAT filesystems family, so why one would tell about partition instead of filesystem? Additionally, partition table displayed by fdisk doesn't list any partition. As to the quote, I don't understand what exactly are these "signature and metadata/magic strings". I can imagine it's like ID consisting of e.g. numbers, but preferably I'd read some formal definition, especially why numbers not letters. By the way, wipefs doesn't show any output in my case. Commented Oct 26, 2018 at 17:15
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To add to the above answer, fdisk can print a warning about a filesystem signature detected if you run it on a partition instead of an entire disk.

Example:

# fdisk /dev/sda1

The device contains 'vfat' signature and it will be removed by a write command. See fdisk(8) man page and --wipe option for more details.

Device does not contain a recognized partition table.

Always run fdisk on an entire disk (e.g. /dev/sda, not /dev/sda1)

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