Quick Fix “Unable to write to the last block of the device”

When Mac users try to format an external hard drive like seagate SSD, Samsung SSD or flash drive using terminal diskutil command it shows error message like “Error: -69760: Disk erase failed with the error Unable to write to the last block of the device”.

Fix 1:-

  1. Connect your external USB disk into a Linux box or Ubuntu and partition it.
  2. Then plug the disk back into the Mac. You can format the Linux created partition with Journaled HFS+.

Fix 2 :-

Try to use 3rd party partition manager apps like GPARTED Live or iPartition apps. These apps will erase your externa; drive and as a new partition.

Fix 3:- (For Windows users/PC)

You can fix a corrupted USB in Windows 7 or 8.

  1. Click the start button.
  2. Type and Enter “cmd” in search field.
  3. In command window type “diskpart” and click Enter button.
  4. Then type “list disk” and click Enter.
  5. Note the disk number associated and note the space that best matches your USB space.
  6. Next type “select disk 1” (use the disk number instead of 1), click Enter.
  7. After that type “clean” and click Enter.
  8. Type “create partition primary” and click Enter.
  9. Type “active” and click Enter.
  10. Type “select partition 1” and click Enter.
  11. Type “format fs=fat32” and click Enter. Now this command start formatting your device.


  1. Restart your mac from Apple menu, and reboot in recovery mode. Then reformat the external drive using disk utility from the recovery partition. It worked like a charm!
  2. Run disk utility from the recovery partition. And format drive in normal would and boot it.

Also try to format your external hard drive with Disk Utility.

Guys I hope this will work you to solve the problem. And if you have any other solutions, let's me know in the comment section below.

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