Software & AppsOperating SystemLinux

How To Recover Data from an SD Card That Won’t Mount: “Can’t Read Superblock” Error

Ubuntu 16

In this comprehensive guide, we will walk you through the process of recovering data from an SD card that won’t mount due to the “Can’t Read Superblock” error. This error typically indicates that the system is unable to read the filesystem’s superblock, which is crucial for mounting the filesystem.

Backing Up the SD Card

Before we begin, it’s essential to create a backup of your SD card. This can be done using the dd command in Linux:

sudo dd if=/dev/mmcblk0 of=/var/tmp/safeplace bs=1024k

In this command:

  • if stands for input file, which is your SD card (/dev/mmcblk0).
  • of stands for output file, which is the backup file (/var/tmp/safeplace).
  • bs stands for block size, which is set to 1024k for faster data transfer.

Checking the Partition Table

The next step is to check the partition table of the SD card. This can be done using the parted command:

sudo parted -l /dev/mmcblk0

This command lists the partition tables for all devices, but the output will be limited to the specific device (/dev/mmcblk0) in this case.

Repairing a vfat Filesystem

If your SD card’s partition type is vfat, the superblock might be corrupted. You can use the fsck.vfat command to check and repair the filesystem:

sudo fsck.vfat /dev/mmcblk0p1

The fsck.vfat command checks a FAT filesystem (which vfat is a type of) and repairs it if necessary.

Handling an exFAT Filesystem

If the SD card was not created on a Linux machine, it might be formatted as exFAT. You can check this by running the following command:

sudo dd if=/dev/mmcblk0p1 bs=16 count=1 | hd

If the output starts with ‘EXFAT’, you need to install the exFAT fuse-based driver:

sudo apt-get install exfat-fuse

After installing the driver, try manually mounting the SD card if it’s not recognized automatically.

Using Testdisk for Recovery

If none of the above steps work, you can use Testdisk, a powerful open-source tool for data recovery. Before using Testdisk, remove the SD card entry from /etc/fstab.

Testdisk can locate and recover files, even from damaged or deleted partitions. You can find detailed instructions on how to use Testdisk on its official documentation page.

When All Else Fails

If all else fails, there is a possibility that the SD card is dead. In this case, check the output of dmesg for more details on the issue.

dmesg | tail

This command displays the system message buffer’s content and can provide useful information about hardware events.

Remember, it’s always crucial to make regular backups of your data to avoid data loss. If you’re frequently encountering issues with your SD cards, it might be time to consider using a more reliable storage solution.

In conclusion, while the “Can’t Read Superblock” error can be daunting, there are several methods to recover your data. Always ensure to back up your data regularly to prevent such situations.

What is a superblock?

A superblock is a data structure in a filesystem that contains important information about the filesystem, such as the size, location of data blocks, and metadata.

How can I create a backup of my SD card?

To create a backup of your SD card, you can use the dd command in Linux. Here’s an example command: sudo dd if=/dev/mmcblk0 of=/var/tmp/safeplace bs=1024k. This command creates a backup file (/var/tmp/safeplace) by copying the contents of the SD card (/dev/mmcblk0) with a block size of 1024k for faster data transfer.

How can I check the partition table of my SD card?

You can use the parted command in Linux to check the partition table of your SD card. For example, sudo parted -l /dev/mmcblk0 will list the partition tables for all devices, but the output will be limited to the specific device (/dev/mmcblk0) in this case.

How can I repair a vfat filesystem?

If your SD card’s partition type is vfat and the superblock is corrupted, you can use the fsck.vfat command. For example, sudo fsck.vfat /dev/mmcblk0p1 will check and repair the vfat filesystem on partition 1 of the SD card.

What should I do if my SD card is formatted as exFAT?

If your SD card is formatted as exFAT, you can check this by running the command sudo dd if=/dev/mmcblk0p1 bs=16 count=1 | hd. If the output starts with ‘EXFAT’, you need to install the exFAT fuse-based driver using the command sudo apt-get install exfat-fuse. After installing the driver, try manually mounting the SD card if it’s not recognized automatically.

What is Testdisk and how can it help with data recovery?

Testdisk is a powerful open-source tool for data recovery. It can locate and recover files, even from damaged or deleted partitions. Before using Testdisk, make sure to remove the SD card entry from /etc/fstab. You can find detailed instructions on how to use Testdisk on its official documentation page.

What should I do if none of the recovery methods work?

If none of the recovery methods mentioned in the guide work, there is a possibility that the SD card is dead. In this case, you can check the output of dmesg using the command dmesg | tail for more details on the issue.

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