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