Apple has a bug in its disk I/O throttling code that affects raw disk copies

Re:Apple has a bug in its disk I/O throttling code that affe... by gabereiser on Saturday June 18, 2022 @11:19AM (#31790598)

This actually bit me earlier this week when I had to write a Windows 11 iso to a usb stick. Using dd on macos, everything seemed like it wrote ok. Checksums matched. All of that. Yet when I booted the target machine with the usb stick, windows installer kept asking for drivers. Back and forth with the motherboard manufacturer and debugging and I narrowed it down to this bug in dd which skipped a few bits (or wrote them incorrectly).

Needless to say, I used a friends windows machine to make an install stick using Microsoft’s media creation tool and that worked out of the box. Strange. The only other explanation I have is that their direct download iso was corrupt or that this dd bug prevented it from writing correctly.

UDF file format. Bootable image. UEFI. SecureBoot enabled. Standard Intel chipset.

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Re:Apple has a bug in its disk I/O throttling code that affe... by pronoiac on Saturday June 18, 2022 @12:05PM (#31791104)

> The only other explanation I have is that their direct download iso was corrupt

I definitely got this impression, after a 2 or 4 gig boundary was crossed. I think I tried a Raspberry Pi to rule out a Mac issue. I had success with https://github.com/WoeUSB/WoeUSB-ng .

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Re:Apple has a bug in its disk I/O throttling code that affe... by stazz1 on Saturday June 18, 2022 @12:16PM (#31791212)

what does a checksum do

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Re:Apple has a bug in its disk I/O throttling code that affe... by pronoiac on Saturday June 18, 2022 @01:07PM (#31791730)

Sorry, I didn't mean "the iso was mangled in transit," I meant "they appear to not understand iso."

The iso checksum verified without issue. Looking into it a bit, this might have something to do with UEFI firmware that only had FAT32 drivers. It started the install fine, but it broke when it hit a 4+ gig file, which would probably look truncated.

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Re:Apple has a bug in its disk I/O throttling code that affe... by stazz1 on Tuesday June 21, 2022 @04:23PM (#31828700)

i'm curious if bits can be altered and the checksum is the same -- it seems like checksum is for file length but not necessarily contents?

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Re:Apple has a bug in its disk I/O throttling code that affe... by withinboredom on Saturday June 18, 2022 @11:35AM (#31790793)

Almost identical problem earlier last month, except it made the drive read-only and had to fix it from Linux. Both Windows and OSX couldn’t fix it.

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Re:Apple has a bug in its disk I/O throttling code that affe... by culpable_pickle on Sunday June 19, 2022 @03:16PM (#31802453)

> and I narrowed it down to this bug in dd which skipped a few bits (or wrote them incorrectly)

Which bug in dd?

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