powercfg /h off

sudo mount /dev/sd** /mnt
sudo grub-install --boot-directory=/mnt/boot /dev/sd*

sudo mount /dev/sd*** /mnt
sudo mount /dev/sd** /mnt/boot/efi
for i in /dev /dev/pts /proc /sys /run; do sudo mount -B $i /mnt$i; done
sudo chroot /mnt
grub-install /dev/sd*
update-grub