This document belongs to Manual Full System Encryption (with Extras): Detailed Process: Set up Boot.
This section describes what the script to refresh Grub does.
It is not necessary to read and understand this page, but it is here for explanation and future understanding.
Remember: You are not supposed to follow these instructions. They are merely an explanation of what you would do if you were to manually perform what the script does.
2. Copy boot modules to EFI
mkdir --parents /boot/efi/EFI/ubuntu/ cp --recursive /boot/grub/x86_64-efi /boot/efi/EFI/ubuntu/
3. Install and repair Grub
Note that the formatting of this page shows as two lines, but it is actually a single line.
Reminder: Change /dev/sdA (at the end of the command) to your primary drive (which is most likely /dev/sda) — this is the same device that you put into Select the bootloader.
grub-install --target=x86_64-efi --uefi-secure-boot --efi-directory=/boot/efi --bootloader=ubuntu --boot-directory=/boot/efi/EFI/ubuntu --recheck /dev/sdA
The next command reconfigures Grub for the machine.
4. Allow Ubuntu to boot
cd /boot/efi/EFI [ -d Boot ] && rm --force --recursive Boot-backup && mv Boot Boot-backup
5. Prepare initramfs
update-initramfs -ck all