Re: dd if=/dev/rdisk12 of=/dev/zero (OT, since macOS)
Date: Sun, 02 Nov 2025 09:09:17 UTC
A last word on the actual error message (Invalid argument) that occured: giving the command the blocksize 4096 makes it pass without an error message. dd if=/dev/rdisk12 of=/dev/null bs=4096 It came to memory again when I recalled that I had a similar problem with the attempt to dump (dd) a CD device. One has to specify bs=2048 with CDROMs. -- Christoph > Am 01.11.2025 um 23:19 schrieb Christoph Kukulies <kuku@kukulies.org>: > > I unmounted the device from the macOS and inserted a 120GB Corsair. > The dd commands works with both, /dev/zero, /dev/null. > No "Invalid argument". > > So it must be faulty hardware. > > Thanks. I think we can close the case :-) > > -- > Christoph > >> Am 01.11.2025 um 23:12 schrieb Christoph Kukulies <kuku@kukulies.org>: >> >> Christophs-MBP:~ root# ls -al /dev/rdisk12 >> crw-r----- 1 root operator 0x100001e Nov 1 23:02 /dev/rdisk12 >> Christophs-MBP:~ root# dd if=/dev/rdisk12 of=/dev/null >> dd: /dev/rdisk12: Invalid argument >> 0+0 records in >> 0+0 records out >> 0 bytes transferred in 0.000052 secs (0 bytes/sec) >> Christophs-MBP:~ root# >>> >> >> >> The drive is new and I haven't done nothing else than mounting it on my macOS. Never written to it. My suspicion is that it is fake hardware. >> Einar, die idea that I /dev/zero is wrong for using in the output direction just came to me a couple of minutes before, but it didn't change anything. >> >> Paul, I just wanted to read every byte from the drive into the kitchen sink. After that dd would write out the number of bytes read. That should be >> >> 10.485.760.000.000 Bytes >> >> >> >>> Am 01.11.2025 um 16:43 schrieb Einar Indridason <einar.indrida@gmail.com>: >>> >>> try using /dev/null as your output. instead of /dev/zero >>> >>> On Sat, 1 Nov 2025, 15:08 Christoph Kukulies, <kuku@kukulies.org <mailto:kuku@kukulies.org>> wrote: >>>> >>>> No, I don't want to use diskutil. I wanted to know why my dd command returns "Invalid argument". >>>> Yes, I know it's OT, sorry for that. The suspicion comes up that I'm fallen victim a fake. So I anted to physically read the device once. >>>> A program like diskutil or system information USB section only transports the faked information. >>>> >>>> Is "Invalid argument" already a consequence of the drive being a fake? >>>> >>>> -- >>>> Christoph >>>> >>>> >>>>> Am 01.11.2025 um 16:00 schrieb paul beard <paulbeard@gmail.com <mailto:paulbeard@gmail.com>>: >>>>> >>>>> Ah. So you want to verify what 'diskutil info rdisk12' returns? >>>>> >>>>> On Sat, Nov 1, 2025 at 7:39 AM Christoph Kukulies <kuku@kukulies.org <mailto:kuku@kukulies.org>> wrote: >>>>>> No no, direction is intentionally read. I just want to read the disk once to get the exact count of bytes and see its integrity. >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> Christoph Kukulies >>>>>> kuku@kukulies.org <mailto:kuku@kukulies.org> >>>>>> >>>>>> >>>>>> >>>>>>> Am 01.11.2025 um 15:32 schrieb Odhiambo Washington <odhiambo@gmail.com <mailto:odhiambo@gmail.com>>: >>>>>>> >>>>>>> >>>>>>> >>>>>>> On Sat, Nov 1, 2025 at 5:10 PM Christoph Kukulies <kuku@kukulies.org <mailto:kuku@kukulies.org>> wrote: >>>>>>>> Hi co-readers, >>>>>>>> >>>>>>>> excuse me for coming up with a non FreeBSD question but I'm sure many "also macOS" users are here. >>>>>>>> I got an SSD external drive today from China. It's supposed to have 10TB and has the name "SEAGATE" engraved on the cover which I haven't opened >>>>>>>> yet, also because it's clipped together - no screws. >>>>>>>> >>>>>>>> Anyway, I tried >>>>>>>> >>>>>>>> >>>>>>>> # dd if=/dev/rdisk12 of=/dev/zero >>>>>>>> >>>>>>>> on it (in a macOS terminal window. >>>>>>>> >>>>>>>> I'm getting >>>>>>>> >>>>>>>> $ sudo dd if=/dev/rdisk12 of=/dev/zero bs=512 >>>>>>>> Password: >>>>>>>> dd: /dev/rdisk12: Invalid argument >>>>>>>> 0+0 records in >>>>>>>> 0+0 records out >>>>>>>> 0 bytes transferred in 0.000036 secs (0 bytes/sec) >>>>>>>> $ >>>>>>>> >>>>>>>> also without the bs=512 not any better. >>>>>>>> >>>>>>>> An ideas what might be wrong? >>>>>>> >>>>>>> You want to wipe the disk, right? So, you write zeros to the raw device, not the other way round. >>>>>>> So it should be something like this: >>>>>>> >>>>>>> dd if=/dev/zero of=/dev/rdisk12 bs=16M count=1000 status=progress >>>>>>> >>>>>>> >>>>>>> >>>>>>> -- >>>>>>> Best regards, >>>>>>> Odhiambo WASHINGTON, >>>>>>> Nairobi,KE >>>>>>> +254 7 3200 0004/+254 7 2274 3223 >>>>>>> In an Internet failure case, the #1 suspect is a constant: DNS. >>>>>>> "Oh, the cruft.", egrep -v '^$|^.*#' ¯\_(ツ)_/¯ :-) >>>>>>> [How to ask smart questions: http://www.catb.org/~esr/faqs/smart-questions.html] >>>>>> >>>>> >>>>> >>>>> >>>>> -- >>>>> Paul Beard / www.paulbeard.org/ <http://www.paulbeard.org/> >>>> >> >