How to repair EFI system partition file system error on external HDD without data loss?

Hi,

To repair an EFI system partition file system error on an external HDD on macOS without data loss, you should first back up your data, then use Disk Utility to run First Aid on the EFI partition and the entire disk. If First Aid doesn't fix the error, you may need to reformat the EFI partition and reinstall macOS, followed by restoring your backed-up data. 

Here's a more detailed breakdown:

1. Back Up Your Data:

• Before attempting any repairs, back up all important data from the external HDD to another storage device using Time Machine or another backup method. This ensures you have a copy of your data in case the repair process fails. 

2. Repair the EFI Partition with Disk Utility:

• Launch Disk Utility on your Mac.
• Select the external HDD from the sidebar.
• Choose "View" > "Show All Devices" to see the EFI partition and the disk itself.
• Select the EFI partition and click on "First Aid".
• Follow the on-screen instructions and click "Run" to check and repair the EFI partition.
• Once First Aid is complete, repeat the process for the entire disk. 

3. If First Aid Fails:

• If Disk Utility reports that the EFI partition or disk is not repairable, you may need to consider reformatting the EFI partition and reinstalling macOS. 
• Back up your data if you haven't already, and then choose "Erase" in Disk Utility. 
• Select the correct disk and partition type (e.g., APFS, macOS Extended (Journaled)). 
• Click "Erase" and follow the on-screen instructions. 
• Reinstall macOS by booting into Recovery Mode (Command-Option-R) and selecting "Reinstall macOS". 
• Restore your backed-up data from Time Machine or your chosen backup method. 

Important Notes:

• If you are running macOS on an Intel Mac, you might need to boot into recovery mode and use Disk Utility to repair the EFI partition. 
• If you are running macOS on an Apple Silicon Mac, the EFI partition might not be present, and the process for repairing the bootloader could be different, according to Apple Support Community. 
• Reformatting the EFI partition will erase all data on it, so be sure you have a backup of your important files before proceeding. 
• If the problem persists, it could be a hardware issue, and you may need to contact Apple Support or a qualified technician for further assistance. 

den.thed wrote:

I recommend that you copy or clone the data to another drive before doing anything else to that drive.

👍 Entirely agree. Without knowing any details about what's on the drive or how it's being used, backing up all the data is the best first step.

@Martin_Smith_65 ... is it a bootable HDD, are you using it for Time Machine, it is just a data drive, exactly what make/model drive is it ... what details can you provide?

It is not clear what is on the external drive or how it is being used.

I recommend that you copy or clone the data to another drive before doing anything else to that drive.

You're welcome.

This is why it is so important to backup both your internal and external drive(s).

We have no idea what is wrong with the Toshiba.

1) Try a different cable between the Toshiba and your Mac.

2) Try connecting the Toshiba to a different Mac and see if it shows up on it.

3) Crack open the Toshiba, remove the drive and put it into a drive dock or on a USB to SATA adapter.

4) Send the Toshiba out to an expensive data recovery service and hope that they can recover all of your files from it.