Steps for Updating the Grub

Boot from live CD/USB. Open terminal emulator and start:

get name of your linux partition:

sudo fdisk -l | egrep '83[ \t]*Linux'
for example it outputs: /dev/sda1

mount it and chroot into it:

sudo mount /dev/sda /mnt
chroot /mnt
restore grub loader:

grub updater will detect list of installed OSes automatically. After that you just need to reboot.

Incase of cannot find a device error:
mount --bind /dev /mnt/dev
chroot /mnt