MacMini2014 no accept Windows efiloader

[Ventero]

Hi everyone.
Is there anyone else here who knows more about historical issues?

I have a 2014 Mac Mini. I have a Windows 10 installation USB flash drive. Previously, I had Windows 10 installed as the only OS on the system’s single hard drive in EFI. After installing Linux Mint, Windows stopped booting, and now the installation USB won’t boot either—I get a “missing operating system” message. I reset the NVRAM using the keyboard shortcut, then ran `nvram -c`, but nothing helped—the Mac now only boots into GRUB2, and the Windows loader won’t start even from the USB flash drive.

The USB flash drive has a single FAT32 partition, and Windows was previously installed from it. After installing Linux, the Mac stopped booting any version of Windows—chainloading from GRUB2 to the installed Windows doesn’t work, the option from the Mac boot menu doesn’t work, and the USB flash drive option from the Mac boot menu (Option + Power) doesn’t work either. Something must have happened to the Mac’s settings. It’s not the USB flash drive.

How do I reconfigure the Mac so that it accepts the Windows efibootloader from the USB flash drive? Are there any specific values in NVRAM that need to be set?

What needs to be done to get macOS to boot the Windows loader?

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I want to turn this into a sort of demo time machine, where the NVMe drive will have Monterey (it’s currently physically disconnected) and the second, separately bootable SATA drive will have Windows 7, Windows 10, and some Ubuntu-based distro without BootCamp. I already had a working Windows 10/7 dual boot, but installing Linux Mint messed it up so badly that I can’t even boot the USB flash drive with the Windows installer anymore.

 

[Snowlover]

Have the same mini, and lost the ability to boot windows 11 after installing biglinux on a separate partition.
Couldn't find a way to fix it, so I ended up booting from an external clone of Monterey, erasing/reformatting the entire internal drive, and reinstalling windows 11 from the rufus made usb drive that was the original installer. Decided to just leave it at that, no more linux.

I don't know why you can't option boot your windows 10 installer. I don't think I tried to boot from my installer before erasing the drive. You my need to erase your drive and start over, and think about doing the linux install alongside Monterey instead of windows.

 

[Ventero]

Thanks for your response.

How did you install Linux? Did you let it install automatically, or did you choose manual configuration? If you chose manual configuration, did you set the boot loader to point to the disk or to the FAT32 EFI partition (e.g., /dev/sdx/ or /dev/sdx1/)?

I followed ChatGPT’s advice and kept the default location for the entire device, even though I remember that partition-based routing was used with EFI.

I think that this way, Linux somehow appropriated that partition and messed it up somehow, so that the files are then unreadable for Windows at the filename level. I’ve encountered this before when I formatted a USB flash drive to FAT32 in Linux and then loaded the Windows installer onto it—it also refused to boot.

But I don’t understand why the standard installer created using MS’s MCT doesn’t work. Maybe it’s because the installer is dual-boot capable for both EFI and MBR, so the partition is marked as active, which I found out the Mac’s firmware won’t accept. I marked the EFI partition as active in DiskPart, and the Mac just flashed a folder icon with a question mark, indicating it couldn’t find the OS. When I unmarked the partition as active, Linux booted into GRUB2 again.

And I found out that I can boot the disk from the GRUB2 console using chainload.
I’ll try removing the active status from the flash drive as well...

I was hoping someone would know a fix so I wouldn’t have to reinstall all three OSes...

 

[Snowlover]

Sorry, I don't really remember. Possibly manual with bootloader on efi partition.
Check out "Windows install" app for reinstalling windows, is quick and easy.

Windows Install

Download Windows Install for free. Installing Windows from macOS. Suitable for Hackintosh and Macintosh. The Windows Install.app program allows you to install Windows directly from the Mac OS system. There is no need to create an installation flash drive.

sourceforge.net

 

[Ventero]

Thanks - I'll take a look.