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FAT32 USB is suddenly read-only on Mac?

My SanDisk Cruzer 32 GB USB, which has been working with no problems for several months, is suddenly read only on Mac. After pressing Command + i, I see the message "You can only read" but can't find a way to change permissions. There's also no lock symbol. I tried to repair it in Disk Utility but failed with an error saying "The underlying task reported failure on exit." I figured I might be able to reformat it but the Erase option is grayed out. Any idea on how to get it to work again?

Best Answered by

iBoysoft author Jenny Zeng

Jenny Zeng

Answered on Wednesday, November 22, 2023

FAT32 has no permissions. Usually, when you check the permissions of a FAT32 drive, it shows the message "You have custom access." When it becomes read-only in a sudden, it may be caused by disk corruption or temporary bugs. I suggest you give the following tips a try:

  • Reboot your Mac with the drive connected.
  • Disconnect and reconnect the drive.
  • Plug the FAT32 drive into a Windows PC to repair it.
  • Log into your Mac with an Admin account.
  • Reformat the USB drive on your Mac via Terminal. 

Here's how to reformat the USB drive to FAT32 in Terminal:

  1. Back up data on the USB.
  2. Open Terminal.
  3. Type the following command and hit Enter.diskutil list
  4. Note down the disk identifier of your USB.
  5. Run the command below to format the USB. (Suppose the disk identifier is disk2 and you want to assign it the name "USB.")diskutil eraseDisk FAT32 USB disk2

Also Read: How to Fix USB Drive is Read Only on Mac Error?

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