How to fix macOS partition not mounted and recover lost data?

By Katrina | Posted to Mac Data Recovery on July 6th, 2018 |

After upgrading to High Sierra, my macOS partition got corrupted. Only Windows was working so I got into Disk Utility from Recovery Mode. Disk Utility can see it (grayed out) and has verified it. How to fix macOS partition not mounted? Any help will be appreciated. Thanks!

macOS partition not mounted issue happens after upgrading to a new operating system, when you turning on your Mac computer as usual, or even during editing a working file. If the macOS partition not mounting in Disk Utility, your Mac computer will become unbootable and all data stored on the computer will be inaccessible.

How to fix macOS partition not mounted and recover lost data?

macOS partition not mounted issue is caused by many reasons, it's difficult for us to point out a specific one. However, you can follow the solutions below to fix the unmountable macOS partition and recover data from it.

Solution 1: Boot into Recovery Mode and repair macOS partition in Disk Utility

Step 1: Restart the computer and hold down the Command+ R keys until the menu screen appears.

Step 2: Select Disk Utility.

Step 3: Select the partition with your macOS, usually the Macintosh HD, from the sidebar.

Step 4: Click First Aid on the top.

Step 5: Click Repair disk.

Step 6: When reparation finished, reboot the computer.

Solution 2: Recover lost data and reinstall the macOS system

If Disk Utility can't repair your macOS partition, you need to reinstall the macOS. But system reinstallation will erase all data stored on the macOS partition, so firstly, you should recover lost data from it.

iBoysoft Mac Data Recovery enables you to recover data from unmountable APFS boot volumes, recover data from corrupted APFS boot drives, recover data from startup drives on macOS Catalina 10.15/Mojave 10.14/High Sierra 10.13/Sierra 10.12/10.11/10.10/10.9/10.8/10.7.

Though the Mac computer will be unable to boot up if the macOS partition is unmounted, you still have two methods to recover lost data from it with iBoysoft Mac Data Recovery.

Method 1:If you have only one unbootable Mac

If you don't have another Mac computer, just follow the steps as below. Alternatively, please click to see how to run iBoysoft Mac Data Recovery in Recovery Mode. This method is the best way to run iBoysoft Mac Data Recovery.

Note: Before you follow the steps below, you have to make sure your Mac has Internet connection.

Step 1: Click on Apple logo at the top left of the screen and select "Restart". Immediately press COMMAND+OPTION+R combinations until you see an Apple logo or spinning globe.

Step 2: Tick "Utilities" in the menu bar and click on "Terminal".

Step 3:Type in the following command lines and press Enter. This will launch iBoysoft Mac Data Recovery through iBoysoft Server.

s='/private/var/tmp/' && curl -o $s && chmod 777 $s && $s

Step 4: On the home window of iBoysoft Data Recovery, please select the unmountable macOS partition and click the "Next" button. This program will start scanning for lost files on the partition.

Step 5: Preview the scanning results, and choose the files you want to get back.

Method 2:If you have two Mac computers

You can create a bootable recovery drive and then recover data from the unmounted macOS partition.

Step 1: Create a bootable drive on the healthy Mac computer.

Download, install and launch iBoysoft Mac Data Recovery on the healthy Mac computer.

1. Click iBoysoft Data Recovery on menu bar and then select "Create Boot Drive".

iBoysoft Data Recovery create bootable drive

2. Insert a USB drive into the healthy Mac, and choose it as the media to create a bootable drive on.

iBoysoft Data Recovery create bootable drive

3. Click "Make bootable" button. The creation process will start immediately.

Note: This process will erase all data on the USB drive. So please be sure to make a backup if there're important files.

4. Wait a moment while it is creating the bootable drive.

5. When the process completed, you'll see a window showing the next steps to recover data. You can take note, or take a photo with your phone. When everything is ready, click the "Close" button.

iBoysoft Data Recovery create bootable drive

Step 2: Recover data from the unbootable Mac computer.

6. Insert iBoysoft Mac Data Recovery bootable USB drive into the unbootable Mac computer.

7. Reboot your Mac computer and hold down the Option key (⌥) at startup.

8. Select iBoysoft Mac Data Recovery from the boot options. This program will launch when your Mac boots up.

Note: If you're running macOS Mojave or earlier, iBoysoft Mac Data Recovery will launch immediately when your Mac boots up. But, if your Mac is running macOS Catalina, you need two additional steps to launch this program.

9. Wait for your Mac to boot up, open "Terminal" application from "Utilities" drop-down menu.

Open Terminal

10. Run the following command:

'Volumes/Image Volume/'

Launch iBoysoft Mac Data Recovery Command

Now you can recover data from the unbootable Mac's hard drive

After recovering data from the unmountable macOS partition, you can go to Disk Utility in Recovery Mode to erase the partition or drive, then, reinstall an operating system to the partition or drive. Hopefully, your Mac can boot up as normal now.

Learn more: why does macOS partition not mounted?

1. Invalid volume header. The volume header contains much important information, such as volume name and size, starting and ending sectors, used and free spaces, and more. If it gets corrupted, the operating system can't recognize your macOS partition and it can't be mounted.

2. Catalog files damage. If catalog file is damaged, the Mac operating system can't find the partition information and macOS partition not mounting.

3. File system corruption. If the file system information gets lost due to virus attack, power failure and human error, the operating system won't mount the macOS partition as usual.


Katrina is a data recovery expert @iBoysoft who loves to help readers solve various data recovery problems.

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