I need to format my USB flash drive first before using it. However, when I connect the USB and am preparing to erase it in Disk Utility, I get the following message:
A writable disk is required.: (-69772).
I think that the flash drive was partitioned, but is protected. I tried to change permissions with “sudo chmod”, but failed. I also tried erasing the USB with “sudo diskutil eraseDisk free EMPTY”, and “diskutil zeroDisk /dev/disk2”, but only got the error saying “A writable disk is required.: (-69772).”
That error usually means the USB stick has gone into a read-only state at the firmware level.
When flash memory detects too many bad blocks, some controllers lock the device so it can’t be written to anymore. That’s why Disk Utility, chmod, and even diskutil eraseDisk all fail with “A writable disk is required.”
Unfortunately, if that’s the case, no software command can re-enable writing. The drive is basically stuck in read-only or completely dead.
However, a few things you can try just to confirm:
Plug the drive into another Mac or even a Windows PC to see if it behaves the same way.
Run diskutil info /dev/disk2 (replace disk2 with the USB’s real identifier) and check the “Read-Only Media” field. If it says “Yes,” the drive is toast.
If you can still access files on the USB drive, copy them out quickly.
Simply download iBoysoft Data Recovery for Mac, select the USB, click Search for Lost Data, check the scanning results, choose the files, and click Recover.