https://help.ubuntu.com/community/Boot-Repair
The easiest way to use Boot-Repair is to burn one of the following disks and boot on it.
Remark : you can also install the ISO on a live-USB (eg via UnetBootin or LiliUSB or Universal USB Installer).
- either from an Ubuntu live-session (boot your computer on a Ubuntu live-CD or live-USB then choose „Try Ubuntu”) or from your installed Ubuntu session (if you can access it)
- connect to the Internet
- open a new Terminal, then type the following commands (press Enter after each line):
sudo add-apt-repository ppa:yannubuntu/boot-repair sudo sed 's/trusty/saucy/g' -i /etc/apt/sources.list.d/yannubuntu-boot-repair-trusty.list sudo apt-get update sudo apt-get install -y boot-repair && (boot-repair &) boot-repair
Alternatywne rozwiązanie
http://howtoubuntu.org/how-to-repair-restore-reinstall-grub-2-with-a-ubuntu-live-cd
sudo fdisk -l sudo mount /dev/sda1 /mnt 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 /dev/sda grub-install --recheck /dev/sdX update-grub exit && sudo umount /mnt/sys && sudo umount /mnt/proc && sudo umount /mnt/dev/pts && sudo umount /mnt/dev && sudo umount /mnt reboot
Jak nie zadziała to spróbujcie to : http://askubuntu.com/questions/145241/how-do-i-run-update-grub-from-a-livecd