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My external hard drive format suddenly changed on Mac?

I recently copied a load of images onto an external hard drive that has only ever been used with a Mac. Yesterday, I relocated about 20000 Aperture preview from a legacy library into the drive and left it running overnight. When I checked the transfer this morning, I saw the"Disk not ejected properly" message and my external hard drive unmounted. I can't get Disk Utility to repair or mount the volume but the disk appears to have no issue and mounted. I notice the unmounted volume is formatted in MS-DOS. This drive was never used on a Windows PC, so how can it be a Windows format? I have just found a PC that can read the drive and back up the file. Is there any way to change the format back to a macOS format without deleting the whole drive?

Best Answered by

iBoysoft author Jenny Zeng

Jenny Zeng

Answered on Wednesday, May 31, 2023

What was your external hard drive formatted with before? If you don't recall, it's likely always MS-DOS, also called FAT32. I think you misunderstood FAT32 as a Windows-only format, which is in fact compatible with both Windows and macOS.

Besides, the only way to convert FAT32 to a Mac format (APFS or Mac OS Extended) is by reformatting, which will delete everything on the drive. If you prefer it as the last resort, you can try other solutions to fix the unmounted FAT32 volume. I suspect that the file transfer process was interrupted by your Mac's power settings, causing it to be improperly ejected.

When this happens, the fsck process may automatically start to repair your drive, resulting it being unmounted. So I suggest you eject the drive, reconnect it with your Mac and wait some time for the repair to complete. If it still won't mount after some time, try quitting the fsck process by executing the following command in Terminal.

sudo pkill -f fsck

If the issue persists, retry running First Aid or you can repair the drive on a Windows PC. If nothing works, it may be the time to reformat your drive. Luckily, you have your files backed up already. For those who still can't access their unmounted drive, they can use iBoysoft Data Recovery for Mac to restore their data before reformatting their drive.

If you don't want to receive the "Disk not ejected properly" notification again, disable the "Prevent computer from sleeping automatically when the display is off" and "Put hard disks to sleep when possible" settings.

Read Also:

How to Format an External Hard Drive on Mac?

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