Two volume USB stick ISO9660-FAT32, ISO9660 volume not working correctly

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Level 1

4 points

Two volume USB stick ISO9660-FAT32, ISO9660 volume not working correctly

I have a USB stick, showing in Disk Utility two 'devices', both named USB Flash Disk Media.

The first device shows up as an uninitiallized device holding an ISO9660 volume with data. The second device shows up as Master Boot Record device with an empty FAT32 volume.

The stick mounts and works perfectly in Windows, but on MacOS (Big Sur and Sonoma) the ISO9660 volume does not work correctly. Certain files cannot be read nor copied, copying files result in error: The Finder can’t complete the operation because some data in FILENAME can’t be read or written. (Error code -36).

I have no info on how this USB stick was created, so I have no clue how one ends up with an uninitiallized device with a ISO9660 volume.

Unmounting the first device doesn't work completely, the ISO9660 volume seems to be unmounted partially, a 'new' ISO9660 volume remains, its size is equal to a compressed (zipped) version of the ISO9660 volume that just was unmounted. Only now the first device can be unmounted completely with Disk Utility.

I was wondering if there's a way to circumvent the error -36 on MacOS, there clearly a problem with the way Mac OS reads this specific ISO image.

Are there any alternative mounting methods/tools that could still allow me to extract/read the data from this ISO image without error -36 ?

Posted on Oct 21, 2024 2:39 PM

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Answer 1

Kurt Lang

Level 9

62,190 points

Oct 21, 2024 2:48 PM in response to AAAFNRAA

This is a common problem, caused by manufacturers who insist on putting hidden garbage on the drives. They're set up such that Windows ignores them, but the Mac doesn't.

Copy any data on the drive to your Mac. Use Disk Utility to erase the entire drive by choosing the drive's physical name in the left column. That will eliminate the hidden junk.

Copy your data back.

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Answer 2

AAAFNRAA Author

Level 1

4 points

Oct 21, 2024 2:59 PM in response to Kurt Lang

Hi Kurt,

Thanks, problem is that on MacOS the data cannot be copied because of the -36 error. As this is an ISO image removing the culprit hidden data is also not an option.

I can of course take a detour via Windows but I like to find a MacOS only solution if possible.

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Answer 3

Kurt Lang

Level 9

62,190 points

Oct 21, 2024 5:11 PM in response to AAAFNRAA

Error 36 means the Finder is having trouble either reading, or writing a file.

By hidden junk, I meant on the USB drive, as indicated by the nonsensical listing of ISO9660-FAT32, ISO9660. Which would be two volumes where there should only be one.

And, what ISO image? I can't tell from what you've written if you're trying to copy this image from the USB drive, or to it from your Mac.

If it's to the drive, then it could easily be a write error. FAT32 cannot handle any single file larger than 4GB. If your ISO image is bigger than that, then that's why the write fails.

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Answer 4

HWTech

Level 9

60,800 points

Oct 21, 2024 6:34 PM in response to AAAFNRAA

Seems like someone "burned" a bootable ISO raw image file to the USB stick. macOS is very limited on being able to read these types of ISO files and resulting USB boot drives since they usually involve drive layouts & file systems that macOS is unfamiliar. At least most ISO files are for making bootable USB sticks, although they don't have to be.

Plus the quality of USB sticks is extremely poor, so you may also be dealing with a hardware issue with that USB stick. IIRC "-36 error code" is an I/O Error which typically is caused by a hardware issue.

If you want the data on the USB stick on your Mac, then use the Windows system to copy the data to another drive formatted with FAT32 or exFAT so you can transfer the data to the Mac.

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