Opencore bootloader suddenly not working

[greshbin]

Hello all,

I'm really hoping someone can help me troubleshoot this odd situation.

I built my hackintosh following this guide. My spec is largely idential. I've had no issues with the build, everything has worked seemlessly. However, out of the blue, the bootloader just stopped working. When the computer starts, the SSD doesn't appear as a bootable drive and no OC bootlist appears. The computer boots straight into Windows, from the Windows SSD.

I checked for changes to the BIOS, and all appears to be fine. The MacOS SSD is detected, but not as a bootable drive.

Fortunately, I have been able to use the original USB key I made during the install to boot opencore and into my MacOS instance.

I have mounted the EFI partition using 'Mount OS EFI.app', and again, all files appear to be present and correct. The OC folder is there with all the files (as far as I can tell).

It's the strangest thing. I've not the slightest idea what to do next.

Please can someone help?

 

[P1LGRIM]

My guess would be that a Windows update has messed up your EFI Partition.

You could try booting from your USB installer and repairing the /EFI.

 

[greshbin]

My guess would be that a Windows update has messed up your EFI Partition.

You could try booting from your USB installer and repairing the /EFI.

I did consider this, but I haddn't been using Windows before this occured. I rarely do.

The previous day, I had been using MacOS as normal. The following day, no bootloader.

I must confess to being quite novice at this. I'm good at following instructions in guides, but beyond that, it's a struggle.

I'd be happy to attempt a repair of the /EFI as you suggest. Where do I start?

Thanks for your support.

 

[Feartech]

I did consider this, but I haddn't been using Windows before this occured. I rarely do.

The previous day, I had been using MacOS as normal. The following day, no bootloader.

I must confess to being quite novice at this. I'm good at following instructions in guides, but beyond that, it's a struggle.

I'd be happy to attempt a repair of the /EFI as you suggest. Where do I start?

Thanks for your support.

assume you could transfer the working EFI over from your USB stick?

 

[P1LGRIM]

Where do I start?

Disconnect the windows drive.
Insert your USB installer flash drive.
Power on and press the boot menu key (usually f11 but YMMV).
At the boot menu select the UEFI of your USB as the boot device.
At the menu screen select your HDD and boot.
At the desktop mount your EFI Partition and replace the /EFI folder with the one from the USB.

 

[greshbin]

assume you could transfer the working EFI over from your USB stick?

Yes, however, I did make a few post-install tweaks to get audio and networking working that I'd prefer to regain. Those tweaks aren't on the USB EFI.

Also, as I mentioned. When I mount the EFI, all the files for OC appear to be present on my MacOS SSD. But for some reason it's not working.

Is there a specific route I can take to figure out why it's not?

 

[greshbin]

I'm going to sleep on this for now. I've posted this late for my time zone, not really expecting so many responses so soon.

I'll check back again tomorrow and pick up any further replies.

Thank you all.

 

[greshbin]

Disconnect the windows drive.
Insert your USB installer flash drive.
Power on and press the boot menu key (usually f11 but YMMV).
At the boot menu select the UEFI of your USB as the boot device.
At the menu screen select your HDD and boot.
At the desktop mount your EFI Partition and replace the /EFI folder with the one from the USB.

Okay, so this is just getting stranger.

I've attempted your suggested process.
I removed the Windows drive, leaving just the MacOS drive.
I selected the usb drive to boot, but no MacOS option appears at the boot menu. The only available options are:

1. Install macOS Big Sur (external)
2. OpenShell.efi
3. Reset NVRAM

I tried moving the drive to the other slot, but got the same result.

Only when reconnecting the Windows drive am I able to select MacOS from the boot menu (with the usb boot key).

If it makes any difference, the drives I'm using are M.2. One for MacOS, one for Windows.

What on earth could be causing this?

Please help.

 

[greshbin]

Hi all, back in the saddle again.

As previously mentioned, I can only boot into MacOS with the Windows SSD connected.

Using the original usb key, I've booted into MacOS and backed up all my files in case of failure.

I've prepared to attempt to replace my internal EFI with the one from the USB boot key, but I've noticed something that makes me a bit uncertian, so I'd like to sense check before proceeding.

When mounting the internal MacOS EFI, this is the folder structure:

EFI /
--- / BOOT
--- / Microsoft
--- / OC

Is this correct? Should the 'Microsoft' folder be here?

I mounted the Windows SSD EFI and the folder is empty.

I'm just wondering if this is part of the problem, i.e. has windows moved its boot efi folder to my MacOS drive causing a conflict?

Please let me know how I should proceed here.

Thank you

 

[trs96]

When mounting the internal MacOS EFI, this is the folder structure:

EFI /
--- / BOOT
--- / Microsoft
--- / OC

Is this correct? Should the 'Microsoft' folder be here?

Sounds like you'd be better off not dual booting with Windows on this machine. In simple terms, Windows has messed with your macOS EFI partition. Start over with a new EFI folder that only has /BOOT and /OC that's all you want there. You'll have to redo the other audio fixes etc. later on.

Read the following guide: https://www.tonymacx86.com/threads/guide-multibooting-uefi-on-separate-drives.198869/

The most important section of the above guide is the Windows part. Going Bald says to create a 207 MB EFI parition for Windows first using Disk Utility. Install Windows to that drive, then disconnect that drive before you install macOS. Where it says OS X you can substitute macOS. The guide was written many years ago before Apple changed the naming scheme.

For Win10:

Connect a drive, insert OS X Install USB, boot the system and at the POST hit the Function hotkey that allows you to select a boot device. Select the OS X Install USB. At the installation screen, select Utilities->Disk Utility and format the drive single partition GUID/Mac OS Extended (Journaled). When done, exit Disk Utility. Quit the OS X installer.

Remove the OS X Install USB and insert the Win10 USB, boot the system and at the POST hit the Function hotkey (F12)? that allows you to select a boot device.

Windows shows up as USB: Win10Installer (or whatever you named the USB) and as UEFI USB: Win10Installer.
Select the UEFI USB: Win10Installer and boot the system.

At the installation screen, select Custom Install. At the next screen select the OS X partition and delete it - do not delete the EFI partition. With the resulting free space hi-lited, install Windows to the space. The installer will create and format the partitions for you. When finished, update and install your 3rd party apps and security suite. Reboot to BIOS/UEFI and disable CSM. Save & exit, continue boot to desktop. Shut down, disconnect the drive.

When you multiboot with Windows, conflicts like this are common unless you isolate the two drives from each other. Some people use a hot swap bay to avoid problems.