Reinstalling Grub Efi Boot Loader

Restore UEFI Boot

Updating your windows 8 to Windows 10 at some point can make your dual-boot machine unable to boot due to grub bootloader damaged.

The first reboot step will bring your system unbootable.

To fix this problem, boot the computer using the SolydXK live USB in UEFI mode, and then chroot into the broken system.

/dev/sda2 is my efi partition

/dev/sda9 is my home partition
/dev/sda10 is my SolydK partition
/dev/sda11 is my SolydX partition







mount the broken system :

sudo mount /dev/sda9 /mnt 

sudo mount /dev/sda2 /mnt/boot/efi 

sudo mount -B /dev /mnt/dev

sudo mount -B /dev/pts /mnt/dev/pts

sudo mount -B /proc /mnt/proc

sudo mount -B /sys /mnt/sys  

make the network available after chrooting :

sudo cp /etc/resolv.conf /mnt/etc/ 
modprobe efivars

chroot into the system :

sudo chroot /mnt

Reinstall grub-efi
For 32 bit system :

 
apt-get install --reinstall grub-efi
update-grub

for 64 bit system :

apt-get install --reinstall grub-efi-amd64
update-grub 

type Ctrl+D to exit chroot

umount all :

sudo umount /mnt/dev

sudo umount /mnt/dev/pts

sudo umount /mnt/proc

sudo umount /mnt/sys 

sudo umount /mnt/boot/efi

sudo umount /mnt  

reboot :

sudo reboot

Your system should be bootable now. Select Windows bootloader and the update proccess will continue to the next step.