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Using GRUB2 as your main boot loader

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The following is for EFI/GPT booting:


Make sure your BIOS is configured to boot from the GRUB2 boot loader and not windows.


Grub 2 can detect windows 10 and certain other operating systems installed on multiple hard drives.  It would be in your best interest to have the ESP on the fastest drive, such as an SSD.


If booting windows, transfer the windows boot loader files to the same partition as the main windows installation and delete the old windows boot partition as it is not needed afterward.  You can search online for how to do this as it is not too complicated.  Download and learn how to use BootICE.


Only have one FAT32/ESP boot partition for GRUB2 and you can chainload to everything else that GRUB2 does not detect. 


If you have linux installed the grub.cfg menu from linux will be your boot menu if you properly install GRUB2 to the ESP.


Keep in mind that if you need custom GRUB2 boot entries such as for Clover or Open Core, they go in the /etc/grub.d/40_custom file of the installed linux distro.


Mount your ESP partition under boot/efi of an installed linux distro such as ubuntu and run in terminal: update-grub.


This will produce a grub.cfg file in /boot/grub that is the boot menu.


Install GRUB2 to the ESP in terminal:


sudo grub-install --target=x86_64-efi --efi-directory=/boot/efi --bootloader-id=ubuntu --recheck --no-floppy --debug


Note that if your linux distro is named something other than ubuntu change

--bootloader-id=ubuntu  to --bootloader-id=your_distro_name


and it will be written to the ESP under that name.


If all of your installed/detected hard drives and EFI operating systems were installed properly they should be visible in the GRUB2 boot menu.


If you have questions about how GRUB2 detects and numbers hard drives/partitions in your hardware setup, you can read the /boot/grub/grub.cfg file of the linux distro.

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