====== GRUB reinstall ======
<code bash>
mount /dev/sda3/mnt
mount /dev/sda1/mnt/boot/efi
for i in /dev /dev/pts /proc /sys; do mount -B $i /mnt$i; done
cp /etc/resolv.conf /mnt/etc
modprobe efivars
chroot /mnt /bin/bash

for i in /sys /proc /dev/pts /dev; do umount /mnt$i; done
umount /mnt/boot/efi
umount /mnt
reboot
</code>