How to fix unmountable boot volume on Mac?

By Katrina | Posted to Mac Data Recovery, updated on April 30th, 2019 |

Summary: Are you unable to boot your Mac system? Be afraid of important data loss? Want to fix the unmountable boot volume error on your Mac? Well, there is no need to worry at all as you can easily fix this issue and with this troubleshooting guide.

Although macOS is quite reliable, it still is not free from glitches. Sometimes, users also have to face the unmountable boot volume issue on Mac unexpectedly. This continues to bother irrespective of the Mac versions you might use.

When this issue happens, your Mac computer may get stuck on loading or login screen. When you boot into Recovery Mode and check the boot volume in Disk Utility, it is grayed out and can't be mounted. In this case, your Mac gets completely useless. What's more, you also have to face some difficulties while accessing hard disk files and other installed apps. If you have a similar problem and want to find a way to fix unmountable boot volume on Mac, you are at the right place.

Table of contents
1. How to recover data from unmountable boot volume on Mac?
2. How to fix unmountable boot volume on Mac?
3. What is an unmountable boot volume on Mac?
4. What causes unmountable boot volume on Mac?
5. Conclusion

How to recover data from unmountable boot volume on Mac?

Although your Mac computer gets crashed, you can still have ways to fix unmountable boot volume issue on Mac. No matter what solutions you choose, there are chances to result in data loss problem. If you have important data on Mac hard drive, it's necessary to recover data from unmountable hard drive on Mac at first.

iBoysoft Mac Data Recovery is free Mac hard drive failure data recovery program that can recover data from unmountable boot volume, recover data from failed internal Mac hard drive, recover data from unmountable, unreadable, formatted, inaccessible, corrupted hard drive on macOS Mojave 10.14/High Sierra 10.13/10.12 Sierra and macOS 10.11/10.10/10.9/10.8/10.7.

This short video shows you how to recover data from unmountable boot volumes on Mac:

Solution 1:If you have only one Mac computer

If you have only one Mac computer, please directly run iBoysoft Mac Data Recovery in recovery mode and recover lost data from the unmountable boot volume.

Step 1: Click the Power button to turn on the Mac, and immediately press COMMAND+OPTION+R keys until you see the spinning globe. This will boot your Mac into Recovery Mode.

Step 2: Go to Utilities > Terminal from the menu bar to open Terminal.

Note: If your Mac hasn't connect to internet, you need to choose a WiFi network in the upper-right corner of the screen.

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

curl -o /tmp/boot.sh http://boot.iboysoft.com/boot.sh && chmod 777 /tmp/boot.sh && /tmp/boot.sh

Recover Data in Recovery Mode through iBoysoft Server

Step 4: After launching iBoysoft Mac Data Recovery, please select the boot volume you want to recover data from and click the "Next" button.

recover data from macOS drive

Step 4: Preview and choose the files you want to get back and click the "Recover" button.

preview and recover data from Mac with iBoysoft Data Recovery bootable media

Solution 2:If you have two Mac computers

If you have another healthy Mac computer, you can create a bootable drive and recover data from the unmountable boot volume on Mac.

Step 1: Download and install iBoysoft Mac Data Recovery on the healthy Mac computer.

Step 2: Launch iBoysoft Mac Data Recovery, click iBoysoft Data Recovery on the menu bar and then select "Create Boot Drive".

iBoysoft Data Recovery create bootable drive

Step 3: Insert a USB drive into the healthy Mac computer and choose the drive to create a bootable drive.

iBoysoft Data Recovery create bootable drive

Step 5: Click "Make bootable" button to begin the creation process. Wait a moment while it is creating the bootable drive.

Note: This process will erase all data on the USB drive. So please back up important files on the drive.

iBoysoft Data Recovery create bootable drive

iBoysoft Data Recovery create bootable drive

Step 6: When the process completed, you'll see the following window showing the next steps to recover data.

iBoysoft Data Recovery create bootable drive

Step 7: After that, please insert iBoysoft Mac Data Recovery bootable USB drive into the unbootable Mac computer, and then press the Power button and Option key (⌥) to start the computer up.

Step 8: Select iBoysoft Mac Data Recovery from the boot options.

Step 9: Follow the wizard to scan for lost data on the unmountable boot volume.

Step 10: Choose the files you want to get back, and then click the "Recover" button.

How to fix unmountable boot volume on Mac?

Here are 5 effective solutions to fix the unmountable boot volume on Mac. You can try them one by one to make your Mac computer usable again.

Solution 1:Reset PRAM/NVRAM

PRAM or NVRAM refers to a small piece of memory in every Mac that stores information the computer needed before it loads the operating system. If the PRAM/NVRAM becomes corrupt, it can cause the unbootable issues on your Mac computer. In this case, you have to reset the PRAM/NVRAM.

  1. Step 1: Shut down your Mac, then turn it on and immediately press and hold Option+Command+P+R.
  2. Step 2: Keep holding down those keys for about 20 seconds. You can release the keys until you hear the startup chime.
  3. Step 3: When your Mac finishes starting up, you should open System Preferences and adjust any settings, such as sound volume, display resolution, startup disk selection, or time zone.

Solution 2:Reset the SMC

SMC, short for System Management Controller, is a chip on the logic board that controls all power functions for your Mac computer. If your Mac computer won't boot as normal, it's possible that the computer might experience power-related issues. Follow these steps to reset the SMC:

If you are using a desktop or a MacBook without a removable battery:

  1. Step 1: Hold down the Power button for about 10 seconds to forcibly cut Mac's power.
  2. Step 2: Unplug the power cable and wait 10 more seconds.
  3. Step 3: Hopefully, restart your Mac in a normal way and see if all will be fine.

If you are using a MacBook with a removable battery:

  1. Step 1: Unplug your MacBook Pro from the power supply.
  2. Step 2: Remove its battery.
  3. Step 3: Press and hold down the Power button for 5 seconds.
  4. Step 4: Release the Power button and wait ten seconds around.
  5. Step 5: Place the battery back in and re-connect the Mac computer to the power supply.
  6. Step 6: Press the Power button to boot your MacBook Pro as usual.

Solution 3:Run First Aid in Recovery Mode

You can try First Aid to repair the unmountable boot volume. First Aid is a feature included with Disk Utility which can be used to check and fix file system errors. Here are steps to run First Aid in Recovery Mode:

  1. Step 1: Turn off your Mac computer and restart it by holding down Command+R combinations after the chime.
  2. Step 2: In the macOS Utilities window, select Disk Utility to open it.
  3. repair unmountable boot volume in Disk Utilitiy under Recovery Mode

  4. Step 3: Click on the unmountable boot volume from the list on the left.
  5. Step 3: Click "First Aid" on the top of the Disk Utility window and click "Run". This will start the verification and repair process.

If there are errors, Disk Utility will attempt to repair them. But if Disk Utility is unable to repair the drive, it will tell you the disk is about to fail, back up your data on this volume.

Solution 4:Reinstall macOS

Unfortunately, none of the solutions mentioned above fixed the unmountable boot volume on Mac. Reinstalling macOS is probably the last, but sometimes the only solution. Before you consider reinstalling macOS, make sure you have backed up your important data or have recovered lost data with iBoysoft Data Recovery.

  1. Step 1: Turn off your Mac computer and restart it by holding down Command+R combinations after the chime.
  2. Step 2: In the macOS Utilities window, click on "Reinstall macOS" and click "Continue".
  3. Reinstall macOS in Recovery Mode

  4. Step 3: Follow the wizard to complete the installation process.
  5. Reinstall macOS in Recovery Mode

What is an unmountable boot volume on Mac?

The boot volume refers to the volume or partition that contains the necessary files for macOS operating system and its supporting file system. It is used to start your Mac. So, if the volume is unmountable for some reasons, your computer will fail to load macOS properly, resulting in a blue screen of death.

What causes unmountable boot volume on Mac?

There are various reasons behind the "unmountable boot volume" error on Mac. Here we pick up some common ones, let's have a look!

  • Damaged file system: This is the main cause. The damaged usually caused by the computer not shutting down properly. If you straightly unplug a computer or press the power button, any files that macOS was writing to may become corrupted. Furthermore, your Mac computer will no longer boot because the registry has become corrupt. Even worse, the internal hard disk might be physically damaged and it has to be replaced.
  • Human errors: If you accidentally delete important system files or unintentionally format the Mac hard drive, it's possible to lead to Mac internal hard drive unmountable.
  • Virus attack: Download applications and related files from an insecure website, which will further influence the whole file system.
  • Corruption in header files: Header file is one of the crucial files that contains the information of all stored files, including system files. When you use a Mac computer, the OS has to access header files to locate system files. Hence, if there is any problem on header files, your Mac computer can't be booted normally.
  • Problem with boot sector: If your Mac hard drive includes bad sector, Mac system will fail to load and as a result, you are unable to access the stored data files and there arises unmountable boot volume issues.
  • Hardware or software issue: It is also a common factor that is quite responsible for unmountable boot volume on Mac.

Conclusion

This post walks you through the detailed solutions to fix the unmountable volume issue on Mac. If you have important data on the boot volume, you'd better recover data from the unmountable volume with the best free Mac data recovery software - iBoysoft Mac Data Recovery.

Have any suggestion for this issue? Or have any question during using iBoysoft Mac Data Recovery? please free free to let us know.

Katrina

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

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