This post introduces how to fix the 'mount failed with 66' error on a Mac when inserting an external hard drive and provides a trusted hard drive recovery tool to help you rescue stored files on the unmountable drive!
Encountering an error message "mount: / failed with 66" when inserting your external hard drive could be such a disappointment. In today's post, we will introduce effective solutions to fix the "mount failed with 66" issue on a Mac, ensuring you won't lose any important files on your hard drive. Let's get started!
When you go to Disk Utility to check the external hard drive you connected that is grayed out and click the "Mount" button to mount it manually, you may receive the error message like "Mount: /failed with 66" or "Couldn't mount [disk name]. (com.apple.DiskManagement.disenter error)". An unmounting error prevents you from accessing stored data on the drive.
Why you can't mount the disk on your Mac? Many reasons can lead to a disk being unable to be mounted on a Mac; here are the common reasons:
File system issues or setting errors can be solved easily and quickly, which does not affect your hard drive data. If the disk is EXT4, which can't be read or written on a Mac computer, you should consider reformating it to a macOS-compatible file system.
After learning the possible reasons for the "Mount failed with 66" issue, you can refer to the step-by-step tutorial to solve the error and access your disk data.
1️⃣Troubleshoot Mac Mount Filed: The first step in troubleshooting the Mac mount, which failed with 66 problems, is to check the physical connection of the external hard disk. Begin by disconnecting the item from your Mac and attaching it to a separate USB port.
Sometimes, the problem is caused by a loose connection or a malfunctioning USB port. This method also works when the common mount error "com.apple.DiskManagement.disenter error -119930868" appears on an external hard drive.
2️⃣Check US Port/Cable: check the USB cable for indications of damage, such as fraying or bending. If you see any damage, replace the cable with a new one. Additionally, ensure that both ends of the connection are firmly inserted into the external hard drive and your Mac.
3️⃣Re-insert Disk: After reinserting the disk and verifying all connections and ports, try mounting the external hard drive on your Mac again. If the mount failed with 66 error continues, use the following troubleshooting steps to remedy the problem.
Here's how to force-mount a disk on Mac via the Terminal command:
Step 1. Type the command below to locate the identifier of the disk you want to mount on your Mac:
diskutil list
Step 2. Launch Terminal and enter this command:
diskutil mount /dev/diskxxx
You should change the "diskxxx" into the identifier for the unmounted disk. It is typically something like disk1s2, or disk2s2, etc. Then, hit "Enter" to confirm the process. And type quit to close the Terminal window.
You can watch this video tutorial to learn the detailed steps:
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If the mount failed issue is due to macOS incompatibility, reformat the drive to a macOS-compatible file system (click to check which one is better👉APFS vs. Mac OS Extended). Note that formatting the disk deletes all data. Before formatting, readers should back up crucial files to avoid data loss.
Step 1. Launch Disk Utility and locate the disk. If you can't find it, click the "Show All Devices" option.
Step 2. Click the "Erase" button at the top menu. Don't forget to choose a suitable file system for your disk.
When you face a "mount failed with 66" error message when trying to mount a disk and access its stored data, EaseUS Data Recovery Wizard for Mac offers you a handy path to access the data in clicks! This useful tool can restore data from an unmountable external hard drive, including images, videos, documents, etc.
Check out the following steps to restore data from a disk when the error "Mount failed with 66" or "Mount failed with 72" shows up so the stored data is not available:
Step 1. Search for lost files
Correctly connect your external hard drive to your Mac. Launch EaseUS Data Recovery Wizard for Mac, and select the external hard drive. Then, click "Search for lost files" to find lost/deleted files on your external devices.
Step 2. Filter and find lost files
After the scan, all file types will be presented in the left panel. Select the file type to find wanted files on your external devices.
Step 3. Preview and recover
Click the file and preview it. Then, select the files you want to recover and click the "Recover" button. You can save your data to local and cloud drives.
This post discusses how to fix the "mount failed with 66" error when connecting a disk on your Mac, including checking and reinserting the disk, running the Terminal command to force-mount the disk, and reformatting the disk to a macOS-compatible file system. Besides, we also provide professional and trusted data recovery software to help you rescue your stored data ASAP! Install EaseUS Mac data recovery software to protect your data all the time!
Here are questions people frequently ask about mount errors on a Mac. Read on to learn more about mount failure on macOS:
1. How do I fix a drive that won't mount my Mac?
Check the cable connections, use Disk Utility to repair the disk, or forcibly mount it using Terminal instructions if a Mac drive won't mount. Hardware problems may need expert help or drive replacement if these procedures fail.
2. Why is my USB flash drive not mounting via the Mac terminal?
Mac Terminal may not mount your USB flash drive due to a faulty file system, mismatched drivers, etc. The common unmounting errors include:
Fix it by running disk repair software, upgrading macOS and USB flash drivers, or verifying hardware connections.
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