My Mac Mini w/ Fusion Drive (that’s a hard disk and an SSD pretending to be a single volume for better performance) froze and wouldn’t boot. Nothing would make it boot normally again. Recovery mode was OK but couldn’t erase the boot volume nor mount it via Disk Utility (I just got “Unable to delete the core storage logical volume”), so reinstalling seemed impossible.
Mac Disk Utility Unable To Unmount Volume For Repair Cost
Unmount the EFI partition! Also unmount WINDOWS partition if you can see it from Mac! Run the Install macOS Sierra from Apps. Restart your PC. Press space while hovering over Install macOS Sierra from Mac HDD, or something similar. Use ONLY 'without caches', at first. Give it a few minutes, install should start. “Couldn’t Unmount Disk” error is an error message that might pop up on your Mac’s screen when the device is not allowed to repair particular permissions or directories in Disk Utility, for instance when trying to repair a hard drive. When a device cannot erase or partition the drive, users are delivered one of.
Fortunately, I figured out how to do it, using some help from a StackExchange post I found. See below for the details.
The magic incantation that fixed it was inspired by instructions I found here:
Note: THIS WILL WIPE YOUR HARD DISK. Only do this if you’re completely ready to just burn it all down to the ground and start over with a blank boot disk.
Here are the steps:
- Boot the recovery volume, which will take you to an OS X Utilities page that shows four options: “Restore From Time Machine Backup”, “Reinstall OS X”, “Get Help Online”, and “Disk Utility”. If you have gotten to this article you have probably already been into Disk Utility a few times already without success, so don’t open Disk Utility.
- From the Utilities menu of the “OS X Utilities” app, open Terminal. (Maximize the terminal window that opens so it’s easier to see the output of the next step.)
- Run diskutil cs list . Using the mouse, copy the long alphanumeric string that’s on the third line of output after “Logical Volume Group”. That’s the Logical Volume Group’s universally unique identifier, a.k.a. its “lvgUUID”.
- LAST WARNING: FROM HERE ON OUT THIS DELETES ALL OF THE DATA ON THE HFS+ LOGICAL VOLUME (but it doesn’t delete the recovery partition).
Run diskutil cs delete FOO-BAR-BIZ-BAZ, where FOO-BAR-BIZ-BAZ was your lvgUUID. This deletes the logical volume group. diskutil will print things about erasing the physical partitions that made up the logical volumes, which in my case were /dev/disk0s2 (a 931GB partition on the internal hard disk) and /dev/disk1s2 (a 113GB partition on the internal SSD). Pay attention to the names of the devices that it just liberated on your system, since you’ll use those device names in the next step.
At this point you have two empty HFS+ partitions that are not a Fusion drive anymore, so you’ll want to rebuild the LVG from those two physical partitions.
- Run this: diskutil cs create'Macintosh HD'/dev/disk0s2/dev/disk1s2 and adjust the /dev/. stuff to include the partitions that diskutil said it erased & mounted in the prior step.
On my Mac Mini it took about a minute to finish.
At this point if you run diskutil cs list you should see just a Logical Volume Group and as many Physical Volumes as you added (which is two in my case, disk0s2 and disk1s2), without any Logical Volumes yet.
- Quit Terminal.app and run Disk Utility from the main “OS X Utilities” app.
Disk Utility should show “Fusion Drive” without any partitions in it, which is expected since we just created the Logical Volume Group without any Logical Volumes in it.
- Select the Fusion Drive and run First Aid on it.
First Aid will immediately create a Logical Volume and format it, leaving one big partition of type”OS X Extended (Journaled)” named “Untitled”.
Now you’re free to do whatever you want with this empty disk. In my case, I erased it and created a new partition named “Untitled” of type “OS X Extended (Journaled, Encrypted)” since I want full-disk encryption.
(I tried to call it “Macintosh HD” during the erase step, but Disk Utility failed to erase the disk and complained that name was invalid, so I just left it as “Untitled”, erased the disk, and then renamed it by selecting the Untitled volume in the left-hand-side list of devices, then clicking on the right-hand-side pane where the name Untitled was shown and editing it there.)
After this, I quit out of Disk Utility, and ran the “Reinstall Install OS X” app. That does a network install which first required me to log in with my Apple ID and then downloaded the install files.
Summary: This post introduces 5 solutions you can try when you are unable to mount an external hard drive on your Mac. Also, to avoid further data loss, you can use iBoysoft Data Recovery for Mac to recover lost data from this unmountable external drive first.
After you connect an external hard drive to your Mac, if everything is working fine, the operating system will automatically recognize, read, and mount your external drive, as well as show it in the Finder and on the desktop.
However, if your disk gives up the ghost just like the users below, the external disk will not be showing up as normal. And if you check it in the Disk Utility, you will find your drive unmounted there.
'I was able to use my 3 TB external hard disk drive to backup my data last week. But now it doesn't mount after I migrate from Mojave to macOS Catalina. I dug around and tried a lot of stuff but still can't mount this external hard drive on my Mac. Can someone explain how to get this drive mounted so I don't lose the data?'
Why an external drive is not mounting on Mac?
There are numerous reasons for the external hard drive not mounting issue. The following are a few of the most common ones:
Hardware and connectivity issue
Most of the time, you can't mount your external drive on a Mac just because the connectivity is not in proper condition. This issue may be affected by a loose fitting, a broken USB cable, the wear on USB ports, etc.
Sometimes, such connectivity issues could make your external drives keep disconnecting, or much worse, it would make your external hard drive unmountable eventually. After all, it is essential to have a firm and tight connection.
Another possible reason for an unmounted disk may come from the problematic hard drive itself. Wonder how could it be? Well, it is possible that you're unable to mount a drive just because it is corrupted and unrecognizable by macOS.
You can recall if your external drive has experienced one of these things: an unsafe removal when you are transferring files, an improper ejection, a sudden power outage, or even a virus infection. If so, your disk might be corrupted and it should be the culprit that you are unable to mount your external drive probably.
Incorrect formatting of the disk
In some cases, an unsupported file system will make your external drive unmountable. It is reasonable because if your Mac can't even read your disk's file system, how can you mount and access this hard drive on your Mac? This factor may not be as possible as the other causes, but it does happen.
Unable to mount external hard drives on Mac, how to fix?
Even though the reasons for a not mounting disk are different from case to case, certainly there are some things you can do to fix this issue. The following are five effective solutions to the 'external hard drives won't mount on Mac' issue, and some of them are just basic checks.
Solution 1: Check and fix connectivity issues
The first thing you can do is to make sure that your disk is connected to your Mac properly.
If you are not sure if there is a problem with the USB port/hub, you can plug a working external drive in to a port/on a hub, unmount and eject it. Then plug the unmountable external hard drive into that port/hub.
Also, here are some things you can try.
- 1. Reconnect your external hard drive to your Mac and ensure that it fits the USB port snugly.
- 2. Connect the external hard drive to a different USB port or a different Mac.
- 3. Replace the USB cable or adapter in case that it was damaged or broken.
- 4. Connect it to a Windows PC and see if the storage device is powered on and working.
Solution 2: Check the file system of the external hard drive
Well, if you don't know exactly what file system your disk is formatted with while your external hard drive can't be mounted now, you can go to Disk Utility to have a check if it is formatted with an unsupported file system.
Remember that macOS is friendly with APFS and HFS+ and is in a neutral attitude with FAT, FAT32, and exFAT. However, it is a different story if you need to access and write to NTFS file system on Mac. By default, macOS only enables NTFS drive read support but disables write support. In this case, you can download a free NTFS driver for macOS to mount this external hard drive in read and write mode.
Still unable to mount the external hard drive on Mac? Then it should be some problems with the drive itself. Then you can go with the following solutions to troubleshoot this problem.
Wait! Have you recovered your important data from this unmountable drive?
Before you go any further to fix this unmountable hard drive, you'd better make sure you have backed up your data on this drive to avoid data loss. The reason is that when your external drive won't mount, you lose the only access to all your files on this drive.
In this situation, if you have important files on the external hard drive, any operations on the drive could overwrite the original data and cause irreparable data loss.
Forget to back up before? You can also use Mac data recovery software like iBoysoft Data Recovery for Mac to recover lost data from the unmountable external hard drives.
iBoysoft Data Recovery for Mac is a free external hard drive data recovery tool that enables you to recover lost data from external drives, especially when a hard drive is unmounted, formatted, inaccessible, unreadable, or corrupted.
It's fully compatible with macOS Big Sur 11/Catalina 10.15/Mojave 10.14/High Sierra 10.13/10.12 and Mac OS X 10.11/10.10/10.9/10.8/10.7. In addition to external hard drive data recovery, it also can recover lost data from internal Mac hard drives, USB flash drives, SD cards, memory cards, pen drives, etc.
Tutorial to recover lost data from unmountable external drive on Mac with iBoysoft Data Recovery for Mac
- 1. Download and install iBoysoft Data Recovery for Mac on Mac, and then restart the computer.
- To use iBoysoft Data Recovery for Mac, you need to install this software on your Mac. You can just download the installation package and install it with no fuss.
- 2. Launch iBoysoft Data Recovery for Mac.
- After successfully downloading this program on your Mac, you can drag it to your Applications folder to install it, or you can double-click its icon to launch it.
- 3. Select the unmountable external drive and click Scan button to scan all lost data.
- When the Mac data recovery software is launched, all connected storage devices will be listed in the interface. You can see the name, file system, and space allocation of your hard drives and partitions. Locate your unmounted external hard drive, select it, and click 'Scan' to scan for lost data.
- Two scanning modes are allowed: Quick scan and Deep scan. Quick scan mode saves time for users and is applied when data is recently deleted. Deep scan mode finds more files at the cost of more time, and it's used when file system is corrupted or partition table is lost. Anyway, this software will automatically choose the most efficient way to scan for files according to the disk condition.
- 4. Preview the searching results, choose files you need, and click Recover to get them back.
- With the preview feature, you can check whether your files on this unmountable disk are in a good condition or not. It saves time and money for users. The software will show if your file is corrupted so that you would not waste energy to recover it or pay for this data recovery product.
- 5. Have a check to ensure you have got all lost data back.
Now you either have a copy of a data backup in hand, or have recovered your important files with iBoysoft Data Recovery for Mac. Therefore, you can go ahead to repair this unmounted external drive without worrying about data loss.
Solution 3: Repair the external hard drive with Disk Utility
When an external hard drive is not working properly, you can use the built-in disk repair tool - First Aid to check and repair disk errors.
- 1. Launch Disk Utility.
- 2. Choose the unmountable external drive on the left sidebar.
- 3. Select First Aid in the top center and click Run.
Solution 2: Repair the external hard drive with Terminal
Sometimes, Disk Utility may not function as desired. Fortunately, you can still try to repair the corrupted external hard drive with Terminal.
- 1. Go to Applications > Terminal
- 2. Enter: diskutil list (This will list out the available volumes).
- 3. Check the volume identifier from the table that appears.
- 4. Enter: diskutil repairVolume [diskvolume identifier]. For example, if the volume identifier of an external hard drive is disk2s, you should enter: diskutil repairVolume disk2s.
Solution 3: Reformat the external hard drive
If yourexternal hard drive can't be repaired with Disk Utility and Terminal, the file system of this drive might be seriously corrupted. The only way to fix this unmountable external drive is to reformat it.
Mac Disk Utility Unable To Unmount Volume For Repair
Warning: Reformatting will erase all data on the external hard drive, so please make sure you have backed up important data. Heroes 3 free for mac.
Mac Disk Utility Unable To Unmount Volume For Repair Mac
- 1. Launch Disk Utility from Utilities.
- 2. Click the icon of the unmountable external drive on the left part of the window.
- 3. Click the Erase function on the top of the Disk Utility window.
- 4. Complete the related information (name, format, scheme), then click Erase button.
Mac Disk Utility Unable To Unmount Volume For Repair Disk
When you can't mount an external hard drive on your Mac, you can try the 5 methods introduced in this post. But no matter which solution you are going to try, to avoid data loss, you are always advised to back up your files or recover your data from this unmountable drive first with iBoysoft Data Recovery for Mac.
But if unfortunately, none of these solutions can make your hard drive work again, or your disk is not even detected or showing up in Disk Utility, then this drive might be physically damaged. Under this situation, you should send it to a local disk repair service and see if they can help.