This text assumes that you know what GRUB is, what it is used for, and have a general understanding of how a computer boots up.
(1) https://wiki.archlinux.org/title/GRUB
(2) https://wiki.archlinux.org/title/EFI_system_partition
(3) https://wiki.archlinux.org/title/Unified_Extensible_Firmware_Interface
Become root user:
$ sudo sh
Mount the pseudo filesystem with EFI variables:
# mount -t efivarfs efivarfs /sys/firmware/efi/efivars
If an error occurs at this stage, you need to boot from external media in UEFI mode.
Mount the EFI partition (if it does not exist, the process of creating it is well described in (2)):
# mkdir -p /esp
# mount /esp
Install the necessary tools:
# ix mut set/boot/efi
Install the bootloader:
# grub-install --target=x86_64-efi --efi-directory=/esp --bootloader-id=GRUB
Configure GRUB to automatically detect all kernels installed in the system realm:
# cat << EOF > /boot/grub/grub.conf
configfile /etc/grub.cfg
EOF
# ix mut system bin/kernel/gengrub