1v

sudo mount /dev/sda2 /mnt
sudo mount /dev/sda1 /mnt/boot
#sudo mount /dev/sda1 /mnt/boot/efi
mkdir /mnt/dev /mnt/proc /mnt/sys
sudo mount --bind /dev /mnt/dev &&
sudo mount --bind /dev/pts /mnt/dev/pts &&
sudo mount --bind /proc /mnt/proc &&
sudo mount --bind /sys /mnt/sys

sudo chroot /mnt

grub-install --target=x86_64-efi /dev/sda

grub-install --recheck /dev/sda

exit &&
sudo umount /mnt/sys &&
sudo umount /mnt/proc &&
sudo umount /mnt/dev/pts &&
sudo umount /mnt/dev &&
sudo umount /mntф


v2/
sudo apt install grub-efi
sudo mkdir /mnt/root && sudo mount /dev/sda2 /mnt/root
sudo mkdir /mnt/efi && sudo mount /dev/sda1 /mnt/efi
sudo grub-install --target=x86_64-efi /dev/sda --efi-directory=/mnt/efi --boot-directory=/media/root/boot


v chrot
mount /dev/sda2 /mnt
mount /dev/sda1 /mnt/boot
mkdir /mnt/dev /mnt/proc /mnt/sys
mount --rbind /dev  /mnt/dev
mount --rbind /proc /mnt/proc
mount --rbind /sys  /mnt/sys
chroot /mnt bash


for i in /dev /dev/pts /proc /sys; do sudo mount -B $i /mnt$i; done