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f3probe: Bad news: The device `/dev/sdd' is a counterfeit of type limbo.

In the manual of f3probe, there is no description of any types of counterfeit media.

What are the other types than limbo, and where are they documented?.

Arronical
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neverMind9
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    To-do: Create tag f3 after surpassing reputation 300. – neverMind9 Mar 02 '18 at 10:27
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    only 3 questions about f3 since 2016, probably no need for a tag. – pim Mar 02 '18 at 13:17
  • @neverMind9 quick reminder.... – cagcoach Dec 21 '20 at 22:05
  • TL;DR: When you see limbo as the output of f3probe, the flash drive(s) you got are fake, in the most common way. The other possible outputs occur if it's just damaged or if it's more sophisticatedly fake. Get your money back and report them. Also: The "fix" command really is a """fix""" and not an actual fix; it means you can then use it for the actual size of the device, as opposed to the counterfeit size. – Andrew May 15 '23 at 05:13

3 Answers3

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They are documented where the rest of the f3 docs are:

The line “Bad news: The device `/dev/sdb’ is a counterfeit of type limbo” summarizes the results presented below this line. The types of drives are good, damaged (seriously failing), limbo (the most common type of fake drives), wraparound (a rare, if existing at all, type of fake drives), and chain (a rare type of fake drives). If you ever find wraparound and chain drives, please consider donating them to my collection.

muru
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The types of known drives are documented in the comments of https://github.com/AltraMayor/f3/libdevs.h:

enum fake_type {
        /* Device is good. */
        FKTY_GOOD,

        /* Device is at least partially damaged. */
        FKTY_BAD,

        /* Device discards data after a given limit. */
        FKTY_LIMBO,

        /* Device overwrites data after a given limit. */
        FKTY_WRAPAROUND,

        /* Device is a sequence of wraparound and limbo regions. */
        FKTY_CHAIN,

        FKTY_MAX
};
  • I think that the region at the beginning of a common chain fake flash drive (first 1 GB?) is a limbo, while the rest is wraparound. – neverMind9 Mar 05 '18 at 12:09
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You can find a quite good and detailed explaination on the Github Issue Page:

FKTY_GOOD: the drive passed f3probe's test with flying colors.

FKTY_BAD: there were repeated I/O errors during the test, or there's no usable segment of good blocks at the beginning of the drive.

FKTY_LIMBO: The drive starts with one segment of good blocks and finishes with one segment of bad blocks. The vast majority of fake drives are of this type. If fake drives didn't have internal caches, a single write to the last block would spot these drives.

FKTY_WRAPAROUND: The drive maps all blocks onto a single segment of good blocks. That is, the drive overwrites old data with new data. This type is rare.

FKTY_CHAIN: The drive maps all blocks onto a segment of good blocks and a segment of bad blocks. That is, the drive overwrites old data with new data and some data is lost right away. This type is very rare. I conjecture that a chain drive is a wraparound drive that degraded some of its good blocks.

cagcoach
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