[cygwin] DD bug fails to wipe last 48 sectors of a disk

[Brian Inglis]

On 2020-06-25 06:08, Hashim Aziz via Cygwin wrote:
> On 24 June 2020 11:21 AM, Andrey Repin wrote:
>> Bottom posting in this channel, please.
>> 
>>> I've just tested with the command:
>> 
>>> dd if=/dev/zero of=/dev/sda iflag=fullblock bs=4M status=progress
>> 
>> oflag=direct
>> 
>> Although I'm unsure how Cygwin/Windows handles it. But without this flag, the
>> write is cached, and the problem may be outside dd, or even Cygwin.
>> 
>>> ...and can confirm that the last 48 sectors remain unwiped in this case also.
>> 
>>> Here is the output:
>> 
>>> 1000182120448 bytes (1.0 TB, 931 GiB) copied, 8284 s, 121 MB/s
>>> dd: error writing '/dev/sda': No space left on device
>>> 238468+0 records in
>>> 238467+0 records out
>>> 1000204861440 bytes (1.0 TB, 932 GiB) copied, 8284.89 s, 121 MB/s

> I have no idea what bottom posting is, mailing lists are new to me and I find
> them a very archaic and noisy way to communicate development changes. I 
> really wish the Cygwin dev team would enter the 21st century and move to a 
> modern development process involving a repository like Github, I'm convinced 
> it would increase developer engagement with the project massively while 
> cutting down on so much of the noise.
> I ran:> dd if=/dev/zero of=/dev/SDA bs=4m oflag=direct status=progress
> ...and can confirm the bug still presents - the last 48 sectors fail to be
> wiped.
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-- 
Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada

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