Followup on this, I noticed it again last night on multiple USB thumbdrives. A dd to the device immediately succeeds (which is weird in itself for large writes of iso sized blobs), but unplugging-replugging shows the writes didn't actually happen. The problem was persistent until I rebooted the machine and it started working normally again. Very weird. I think the microSD was probably fine and the hosage was at the USB or something other than the hardware level. It might be related to unplugging a mounted device at some point. Any ideas are welcome.
On Tue, Mar 6, 2018 at 8:29 PM, Russell Senior <russ...@personaltelco.net> wrote: > https://www.youtube.com/watch?v=r3GDPwIuRKI > > On Tue, Mar 6, 2018 at 8:22 PM, Russell Senior > <russ...@personaltelco.net> wrote: > > Yeah, I understood about the on-SD controller. There is typically > > some kind of ARM-based microcontroller that does all the block-device > > to NAND translation. It is doing something wrong and clearly > > dysfunctional now, though. I am sure that I did successful block > > operations on the same microSD previously. > > > > On Tue, Mar 6, 2018 at 5:31 PM, Tomas Kuchta > > <tomas.kuchta.li...@gmail.com> wrote: > >> When I said card controller, I meant the card controller on/in the > actual > >> SD card. Not the piece of HW attached to your computer. > >> > >> My conclusion at the time I was trying to understand the same behavior > was > >> that the in-card controller must be doing file transactions of some > kind. > >> Not behaving quite like basic block device. > >> > >> I recall even trying to actively corrupt the card's content, no success. > >> Still, all worked fine when installing Linux on said cards. > >> > >> Hope it helps you avoiding wasting whole day or three on this, like I > did. > >> > >> Tomas > >> > >> On Mar 7, 2018 9:23 AM, tomas.kuchta.li...@gmail.com wrote: > >> > >>> I do not believe that SD cards respond to pure raw block writes from > dd. > >>> Not unless the stream looks like files. > >>> > >>> I run into the same discovery some time ago. If I remember correctly, > dd > >>> didn't overwrite the content even with random data. It could behave > >>> different for different firmware, but I tried a few with the same > result. > >>> > >>> Tomas > >>> > >>> On Mar 7, 2018 9:13 AM, "wes" <p...@the-wes.com> wrote: > >>> > >>> that's only if you want to generate a certain size. otherwise it just > keeps > >>> going until it runs out of blocks to fill. > >>> > >>> -wes > >>> > >>> On Tue, Mar 6, 2018 at 5:08 PM, Tim Garton <garton....@gmail.com> > wrote: > >>> > >>> > Don't you need a "count=#" option to dd as well? Not at a computer > right > >>> > now otherwise I'd be able to check if that's the case... > >>> > > >>> > On Mar 6, 2018 5:02 PM, "Richard England" <rlengl...@frontier.com> > >>> wrote: > >>> > > >>> > > On 03/06/2018 04:20 PM, Tomas Kuchta wrote: > >>> > > > >>> > >> Try to delete the original files first. Then create empty file > using > >>> > >> /dev/zero and copy it to the card. I bet that it will be there on > the > >>> > card > >>> > >> and some of your original data will disappear as result. > >>> > >> > >>> > >> My guess is that the card controller is deduplicating your > /dev/zero > >>> > >> blocks > >>> > >> trying to protect the card from writes. > >>> > >> > >>> > >> Tomas > >>> > >> > >>> > >> On Mar 6, 2018 7:09 PM, "Russell Senior" < > russ...@personaltelco.net> > >>> > >> wrote: > >>> > >> > >>> > >> On Tue, Mar 6, 2018 at 3:04 AM, Russell Senior > >>> > >>> <russ...@personaltelco.net> wrote: > >>> > >>> > >>> > >>>> On Tue, Mar 6, 2018 at 3:01 AM, Jim Karlock < > jjkarl...@gmail.com> > >>> > >>>> wrote: > >>> > >>>> > >>> > >>>>> My initial attempt to google this was unsuccessful (most people > >>> point > >>> > >>>>>> out the write protect tab, not my problem). > >>> > >>>>>> > >>> > >>>>> > >>> > >>>>> Bad switch on the write protect tab? (The tab operates a tiny > >>> > switch.) > >>> > >>>>> > >>> > >>>> Nope. > >>> > >>>> > >>> > >>>> I can turn the switch to lock and it mounts the device read only > >>> very > >>> > >>>> clearly. The behavior I observe is that it happily writes > /dev/zero > >>> > >>>> over the block device, but then when I read again, the old data > is > >>> > >>>> still present. > >>> > >>>> > >>> > >>> For example, if I flip the tab to write protect tab to "Lock", I > get > >>> > >>> this: > >>> > >>> > >>> > >>> # dd if=/dev/zero of=/dev/sdc status=progress bs=1M > >>> > >>> dd: failed to open '/dev/sdc': Read-only file system > >>> > >>> _______________________________________________ > >>> > >>> PLUG mailing list > >>> > >>> PLUG@pdxlinux.org > >>> > >>> http://lists.pdxlinux.org/mailman/listinfo/plug > >>> > >>> > >>> > >>> _______________________________________________ > >>> > >> PLUG mailing list > >>> > >> PLUG@pdxlinux.org > >>> > >> http://lists.pdxlinux.org/mailman/listinfo/plug > >>> > >> > >>> > > > >>> > > |Perhaps using dd if=/dev/urandom |of=/dev/sdc status=progress > bs=1M > >>> > > ...just a thought. > >>> > > > >>> > > _______________________________________________ > >>> > > PLUG mailing list > >>> > > PLUG@pdxlinux.org > >>> > > http://lists.pdxlinux.org/mailman/listinfo/plug > >>> > > > >>> > _______________________________________________ > >>> > PLUG mailing list > >>> > PLUG@pdxlinux.org > >>> > http://lists.pdxlinux.org/mailman/listinfo/plug > >>> > > >>> _______________________________________________ > >>> PLUG mailing list > >>> PLUG@pdxlinux.org > >>> http://lists.pdxlinux.org/mailman/listinfo/plug > >>> > >>> > >>> > >> _______________________________________________ > >> PLUG mailing list > >> PLUG@pdxlinux.org > >> http://lists.pdxlinux.org/mailman/listinfo/plug > _______________________________________________ PLUG mailing list PLUG@pdxlinux.org http://lists.pdxlinux.org/mailman/listinfo/plug