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] >
