I git clone'd f3, a tool for testing sd cards, and it f3probe reports both of the micro SD cards I was trying to write as damaged. I found a third micro SD card that is not damaged, which implies the problem is with the cards, not the computer or reader. Just unlucky, I guess. The fact that the first two cards I found were on the table next to me might have been a clue that they'd come out of something and maybe they came out of them FOR A REASON. I put a big Sharpie X on the two bad ones to give me more of a clue for next time. It is interesting that I can still read from them, just not write.
On Sat, May 9, 2026 at 8:45 PM Russell Senior <[email protected]> wrote: > > On Sat, May 9, 2026 at 3:56 PM Ted Mittelstaedt <[email protected]> > wrote: > > > > Have you tried a different card reader in a different computer? > > I think I literally said that in the second paragraph, but yes. On > plugging via a USB dongle, dmesg says it is writable: > > [Sat May 9 20:06:58 2026] usb 3-2: new high-speed USB device number > 18 using xhci_hcd > [Sat May 9 20:06:58 2026] usb 3-2: New USB device found, > idVendor=05e3, idProduct=0751, bcdDevice=14.04 > [Sat May 9 20:06:58 2026] usb 3-2: New USB device strings: Mfr=3, > Product=4, SerialNumber=0 > [Sat May 9 20:06:58 2026] usb 3-2: Product: USB Storage > [Sat May 9 20:06:58 2026] usb 3-2: Manufacturer: USB Storage > [Sat May 9 20:06:58 2026] usb-storage 3-2:1.0: USB Mass Storage device > detected > [Sat May 9 20:06:58 2026] scsi host0: usb-storage 3-2:1.0 > [Sat May 9 20:06:59 2026] scsi 0:0:0:0: Direct-Access Generic > STORAGE DEVICE 1404 PQ: 0 ANSI: 6 > [Sat May 9 20:06:59 2026] sd 0:0:0:0: Attached scsi generic sg0 type 0 > [Sat May 9 20:06:59 2026] sd 0:0:0:0: [sda] 31116288 512-byte logical > blocks: (15.9 GB/14.8 GiB) > [Sat May 9 20:06:59 2026] sd 0:0:0:0: [sda] Write Protect is off > [Sat May 9 20:06:59 2026] sd 0:0:0:0: [sda] Mode Sense: 21 00 00 00 > [Sat May 9 20:06:59 2026] sd 0:0:0:0: [sda] Write cache: disabled, > read cache: enabled, doesn't support DPO or FUA > [Sat May 9 20:06:59 2026] sda: sda1 > [Sat May 9 20:06:59 2026] sd 0:0:0:0: [sda] Attached SCSI removable disk > [Sat May 9 20:07:00 2026] EXT4-fs (sda1): recovery complete > [Sat May 9 20:07:00 2026] EXT4-fs (sda1): mounted filesystem > 40af6f66-8d84-45b4-b056-9a2ee4c5a7b5 r/w with ordered data mode. Quota > mode: none. > > umount /dev/sda1 > > [Sat May 9 20:08:02 2026] EXT4-fs (sda1): unmounting filesystem > 40af6f66-8d84-45b4-b056-9a2ee4c5a7b5. > > # time dd if=/dev/urandom of=/dev/sda bs=128k status=progress oflag=sync > 15921446912 bytes (16 GB, 15 GiB) copied, 863 s, 18.4 MB/s > dd: error writing '/dev/sda': No space left on device > 121549+0 records in > 121548+0 records out > 15931539456 bytes (16 GB, 15 GiB) copied, 863.936 s, 18.4 MB/s > > real 14m23.938s > user 0m0.749s > sys 2m5.471s > > [Sat May 9 20:23:31 2026] sda: sda1 > > like, why is there still a partition? > > # time dd if=/dev/zero of=/dev/sda bs=128k status=progress oflag=sync > 15915155456 bytes (16 GB, 15 GiB) copied, 751 s, 21.2 MB/s > dd: error writing '/dev/sda': No space left on device > 121549+0 records in > 121548+0 records out > 15931539456 bytes (16 GB, 15 GiB) copied, 752.161 s, 21.2 MB/s > > real 12m32.163s > user 0m0.634s > sys 0m19.809s > > [Sat May 9 20:36:49 2026] sda: sda1 > > Unplug and replug, dmesg says: > > [Sat May 9 20:39:21 2026] usb 3-2: USB disconnect, device number 18 > [Sat May 9 20:39:25 2026] usb 3-2: new high-speed USB device number > 19 using xhci_hcd > [Sat May 9 20:39:25 2026] usb 3-2: New USB device found, > idVendor=05e3, idProduct=0751, bcdDevice=14.04 > [Sat May 9 20:39:25 2026] usb 3-2: New USB device strings: Mfr=3, > Product=4, SerialNumber=0 > [Sat May 9 20:39:25 2026] usb 3-2: Product: USB Storage > [Sat May 9 20:39:25 2026] usb 3-2: Manufacturer: USB Storage > [Sat May 9 20:39:25 2026] usb-storage 3-2:1.0: USB Mass Storage device > detected > [Sat May 9 20:39:25 2026] scsi host0: usb-storage 3-2:1.0 > [Sat May 9 20:39:26 2026] scsi 0:0:0:0: Direct-Access Generic > STORAGE DEVICE 1404 PQ: 0 ANSI: 6 > [Sat May 9 20:39:26 2026] sd 0:0:0:0: Attached scsi generic sg0 type 0 > [Sat May 9 20:39:27 2026] sd 0:0:0:0: [sda] 31116288 512-byte logical > blocks: (15.9 GB/14.8 GiB) > [Sat May 9 20:39:27 2026] sd 0:0:0:0: [sda] Write Protect is off > [Sat May 9 20:39:27 2026] sd 0:0:0:0: [sda] Mode Sense: 21 00 00 00 > [Sat May 9 20:39:27 2026] sd 0:0:0:0: [sda] Write cache: disabled, > read cache: enabled, doesn't support DPO or FUA > [Sat May 9 20:39:27 2026] sda: sda1 > [Sat May 9 20:39:27 2026] sd 0:0:0:0: [sda] Attached SCSI removable disk > [Sat May 9 20:39:27 2026] EXT4-fs (sda1): recovery complete > [Sat May 9 20:39:27 2026] EXT4-fs (sda1): mounted filesystem > 40af6f66-8d84-45b4-b056-9a2ee4c5a7b5 r/w with ordered data mode. Quota > mode: none. > > wtf? > > Same thing seems to be happening on another micro SD card on an mmcblk > interface on a different computer. > > > Sent: Saturday, May 9, 2026 2:15 PM > > To: Portland Linux/Unix Group <[email protected]> > > Subject: [PLUG] writing to micro SD card and not writing to micro SD cards > > AT THE SAME TIME??? > > > > I was trying to reformat some microSD cards last night. They are apparently > > writable, mount rw. I umount them, use (CAREFULLY) dd to write /dev/zero or > > /dev/urandom on to them and dd seems to happily do it. I can even hexdump > > back out the zeros or whatever back out, for a short time. But moments > > later, all the original content is still there. > > > > I have tried multiple computers, two different microSD cards, multiple > > distribution versions, interface adapters, including your usual USB > > adapters and mmcblk adapters, same result. It isn't a write protect slide > > switch, because there aren't any in some of those adapters and anyway, in > > the case where there was one, it was in the correct position. > > > > Anyone know what's going on? > > > > -- > > Russell Senior > > [email protected] > >
