How to Fix First Aid Could Not Unmount the Volume for Repair

When attempting to use Disk Utility's First Aid feature, you'll see the "First Aid could not unmount the volume for repair" error message. This error stops the repair process and can cause worry due to the possibility of data loss. 

It usually happens when Disk Utility can't unmount a volume to perform a repair. If the system can't unmount the volume, it likely means that some processes still use the disk, preventing Disk Utility from accessing it. 

Why the First Aid Could Not Unmount the Volume for Repair

There are several reasons why the "first aid could not unmount the volume for repair" error might appear. Identifying the root cause can help you address the issue more effectively:

• Active Processes or Applications: One of the most common reasons is that some applications or processes still use the volume. This could include background processes, open files, or even running applications. To identify this, you can use the Activity Monitor to check if any processes actively use the disk.
• File System Corruption: Corrupted file systems can also prevent unmounting. In such cases, even though no applications actively use the disk, the system cannot unmount it due to internal errors. This might be evident if you notice frequent system crashes or unusual behavior related to the disk.
• Hardware Issues: Physical problems with the hard drive or connection can also lead to this error. This can be diagnosed by checking the disk's health status using the Disk Utility's "S.M.A.R.T. Status" feature or other third-party tools.

Fix the First Aid Could Not Unmount the Volume for Repair

Before trying any solutions below, back up your data to avoid potential data loss.

Method 1. Use Safe Mode to Unmount the Volume

Mac Safe Mode disables non-essential system processes, which might prevent the volume from unmounting.

Step 1. Restart your Mac and immediately press and hold the "Shift" key.

Step 2. Release the Shift key once the Apple logo appears. Your Mac will boot into Safe Mode.

Step 3. Open "Disk Utility" and try to run "First Aid" again.

Step 4. If successful, restart your Mac normally.

Method 2. Unmount the Volume Using Terminal

If Disk Utility fails to unmount the volume, you can try using Terminal to force the unmount process.

Step 1. Open "Terminal" from the "Utilities" folder or search for it using Spotlight.

Step 2. Type the following command and press "Enter": diskutil list.

Step 3. Identify the "identifier" of the disk you want to unmount (e.g., disk2s1).

Step 4. Type sudo diskutil unmount force /dev/disk2 (replace disk2 with your disk identifier) and press "Enter."

Step 5. If the volume unmounts successfully, run First Aid from Disk Utility again.

Method 3. Use Recovery Mode to Repair the Disk

MacOS Recovery Mode offers tools to fix your disk issues when regular booting fails.

Step 1. Restart your Mac and press the "Command" + "R" keys immediately.

Step 2. Release the keys when you see the Apple logo or a spinning globe. Your Mac will boot into Recovery Mode.

Step 3. Select "Disk Utility" from the macOS Utilities window.

Step 4. Select the volume and click "Unmount." If successful, run "First Aid."

Step 5. If the unmount fails, erase the disk only after confirming you have a data backup.

Method 4. Erase the Disk and Reformat It

If all else fails and you have a backup, erasing and reformatting the disk may be the only option.

Step 1. Boot your Mac into Recovery Mode by pressing "Command" + "R" during startup.

Step 2. Select "Disk Utility" and choose the disk you want to erase.

Step 3. Click "Erase," choose a format (like APFS or Mac OS Extended), and confirm the operation.

Step 4. After erasing, use "First Aid" to check the newly formatted disk.

Step 5. Restore your data from the backup once the disk is repaired and ready.

Recover Data from Unmountable Hard Disk on Mac

When your Mac encounters this issue, you might potentially lose data. Fortunately, you can get a specialized data recovery tool such as EaseUS Data Recovery Wizard for Mac.

It's designed to handle data loss situations, including unmountable Mac disks recovery. 

Here are some of the key functions of EaseUS Data Recovery Wizard for Mac:

• Comprehensive File Recovery: It can recover photos, documents, videos, and more from unmountable disks, ensuring you retrieve all critical data.
• Mac Compatibility: The software is optimized for macOS, providing seamless recovery without compromising system performance.
• Deep Scanning: You can select quick scans for recently deleted files or deep scans for more complex recoveries.
• Preview Recovery: It lets you preview files to ensure you retrieve exactly what you need. 

Step 1. Scan for lost data on the fusion drive

Select the Fusion Drive partition where you lost data and files. Click the "Search for lost files" button. If you don't know which partition is the fusion drive, click the "search from your disk" anchor text to check the partition name.

Step 2. Find lost files after the scan

EaseUS Data Recovery Wizard for Mac will immediately scan your Fusion disk partition and display the scanning results. You can filter the files through the file type and path.

Step 3. Recover files on the fusion drive

In the scan results, select the file(s) to preview. Then, click the "Recover" button to get them back.

Final Words

Mac users might see the "First Aid could not unmount the volume for repair" error because of active processes, file system issues, or hardware problems. You can try solving it using Safe Mode, Terminal commands, Recovery Mode, or erasing the disk.

If you have trouble fixing your disk or are worried about losing data, a trustworthy tool like EaseUS Data Recovery Wizard can help keep your important files safe. 

First Aid Could Not Unmount the Volume for Repair FAQs

In this section, you'll get answers to common queries about first aid not being able to unmount the volume for repair.

1. How to Fix Volume Could Not Be Unmounted?

To fix the "volume could not be unmounted" error like couldn't unmount disk 69888, use Safe Mode to reduce system interference or force the volume to be unmounted using Terminal. If these methods fail, booting into Recovery Mode and attempting the repair from there can often resolve the issue. After ensuring your data is backed up, you might need to erase and reformat the disk.

2. How to Fix Couldn't Unmount Disk Error on Mac?

To resolve the "couldn't unmount disk" error on Mac, start by closing any applications that may be using the disk. If this doesn't work, use Terminal commands to force an unmount. Another option is to boot your Mac into Recovery Mode and repair the disk using Disk Utility. As a last resort, you may need to erase the disk and restore your data from a backup.

3. What Does "Unmount Volume" Mean?

"Unmount volume" refers to safely disconnecting a disk or partition from the operating system, ensuring that no data is being written or read during the disconnection. This is necessary for repairs, formatting, or removing the disk from the system.

4. How Do I Force My Mac to Unmount a Disk?

To force your Mac to unmount a disk, you can use Terminal. By typing diskutil unmount force /dev/diskX, you can force the unmount process, replacing diskX with the identifier of the disk you wish to unmount. Alternatively, you can attempt to unmount the disk in Recovery Mode or Disk Utility in Safe Mode.