SD card Problems:

[last updated: 2019-11-24]
go to: raspberry Pi home page
go to: SD card home page
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• (link to:) Great post of all or most boot issues
• Bad Superblock:
• In the process of trying to get a TFT LCD module driver installed, I managed to "break" four SD cards. That is, they won't boot in rPi. The boot process starts, but hangs at various places.
• Initially when inserted into an SD card reader, and insert the reader into my Linux desktop running Mint 19.2 ...
• Even though the red light on the reader is lit, the SD card doesn't show up in list of "removable drives" (icon in lower menu tray).
• ... ..., and I can't see them in File manager nor with fdisk.
• $ dmesg however does show the drive (sdf) when I insert it in the card reader.
  "[sdf] Attached SCSI removable disk"
• so I created a mount point with:
  $ cd /media/jay
  $ sudo mkdir sdf
• then attempted to manually mount with:
  $ sudo mount /dev/sdf1 /media/jay/sdf
  (also tried $ sudo mount /dev/sdf /media/jay/sdf - same result)
  but failed with:
  "mount: /media/jay/sdf: wrong fs type, bad option, bad superblock on /dev/sdf1,
  missing codepage or helper program, or other error."
• Investigating further:
  I see that File manager for /dev shows line items for sdf and sdf1 when (only when) SD reader is plugged in
• Next I see that:
  $ sudo fdisk -l shows sdf1 is Type: W95 FAT32
• $ sudo fsck.vfat -v /dev/sdf1 returns:
  fsck.fat 4.1 (2017-01-24)
  Logical sector size is zero.
• inserting SD05 auto mounts and opens file manager windows for /root, /boot, & /SETTINGS
  then executing $ sudo fdisk -l returns:
  Device Boot Start End Sectors Size Id Type
  /dev/sdf1 8192 3275390 3267199 1.6G e W95 FAT16 (LBA)
  /dev/sdf2 3275391 31116287 27840897 13.3G 5 Extended
  /dev/sdf5 3276800 3342333 65534 32M 83 Linux
  /dev/sdf6 3342336 3483647 141312 69M c W95 FAT32 (LBA)
  /dev/sdf7 3489792 31116287 27626496 13.2G 83 Linux

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• SD card corruption:
• At some point I started losing files. That is, when I was working with python files, I would make edits, and they would seem to be saved, but if I rebooted, the changes were lost.
• Forums suggested my SD card had been corrupted, probably from repeated power-downs without having done an orderly shutdown of the op sys (ie with $ sudo shutdown).
• It was advised that, if you do need to do a power-down without having done an orderly shutdown, at least note the processor activity LED (green) on the rPi, because if it's flashing, that indicates it's in the process of reading/writing to the SD card, and if you power down while that's going on, it will increase the likelihood of SD corruption.
• So I'm researching an external pushbutton circuit that will initiate a proper shutdown, to be used prior to powering down.

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