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GRUB2 and Chainloading Open Core 0.6.5 and newer.


HenryV
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GRUB2 and Chainloading Open Core 0.6.5 and newer.

 

Through version 0.6.4 chainloading was relatively simple. It now appears that Open Core 0.6.5 and newer have undergone code change that prevents chainloading the OpenCore.efi directly from GRUB2.

 

However, if you want to continue to use GRUB2 as your main ESP bootloader, you can install Refind 0.13.2 to your ESP alongside GRUB2 and chainload to Refind in grub.conf with the following (where xxxx:xxxx is your ESP UUID}:

 

menuentry "refind"{
   insmod part_gpt
   search --no-floppy --set=root --fs-uuid xxxx-xxxx
   chainloader /EFI/refind/refind_x64.efi
}

 

You may have to change the Vault configuraton in Open Core config.plist from Secure to Optional.

 

Here is a sample refind.conf that will chainload Open Core 0.6.7 (where xxxx is the volume name of your Open Core partition:

 

menuentry "OpenCore 0.6.7" {
    icon /EFI/refind/icons/os_mac.png
    volume xxxx
    loader /EFI/OC/OpenCore.efi
    options "-v"   
}

 

This is an extra step but it preserves GRUB2 as the main bootloader and facilitates use of newer Open Core version 0.6.7.

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  • 4 months later...

Hi,

 

I am not sure where you got that information from, but that is incorrect.

You can chainload both in the same way or by pointing to /EFI/OC/OpenCore.efi .

You may need to clear the NVRAM though because in my experience things stay behind there that may prevent it from working correctly.

I had the issue that OpenCore would directly load from UEFI(BIOS) fine, but chainloading would sometimes work and sometimes not.

After using the ClearNvram entry in the latest OC (0.7.2) it worked without issues.

It is also unclear to me if OpenCore does not change the way windows 'sees' the hardware.
I think there are options to prevent that and I have no issues using OpenCore itself as main bootloader either.
I have triple boot and used efimgr to add the Linux entry as described here:

https://github.com/dortania/OpenCore-Multiboot/blob/master/oc/linux.md

 

I had to boot other OSes a few times to get OpenCore to pick it up.
As described in the guide, OpenCore will show EFI as a boot option.
That is simply the label of the EFI partition. I changed that to UBUNTU_EFI and now I have a nice and clear login screen with three OSes.

 

cheers

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On 8/18/2021 at 6:00 AM, Openminded said:

Hi,

 

I am not sure where you got that information from, but that is incorrect.

You can chainload both in the same way or by pointing to /EFI/OC/OpenCore.efi .

You may need to clear the NVRAM though because in my experience things stay behind there that may prevent it from working correctly.

I had the issue that OpenCore would directly load from UEFI(BIOS) fine, but chainloading would sometimes work and sometimes not.

After using the ClearNvram entry in the latest OC (0.7.2) it worked without issues.

It is also unclear to me if OpenCore does not change the way windows 'sees' the hardware.
I think there are options to prevent that and I have no issues using OpenCore itself as main bootloader either.
I have triple boot and used efimgr to add the Linux entry as described here:

https://github.com/dortania/OpenCore-Multiboot/blob/master/oc/linux.md

 

I had to boot other OSes a few times to get OpenCore to pick it up.
As described in the guide, OpenCore will show EFI as a boot option.
That is simply the label of the EFI partition. I changed that to UBUNTU_EFI and now I have a nice and clear login screen with three OSes.

 

cheers

Thank you for the reply.

 

My intent was to keep GRUB2 as the main boot loader.

 

There was no problem chainloading Open Core directly until 0.6.5.  After that I chainloaded it with refind. 

 

If the code base has changed to again permit directly chainloading Open Core from GRUB2, that will be fine.

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