ubuntu boot-repair

When the shit goes down, you’ve lost grub (as I did earlier :)) this is the tool you need!
Ubuntu – Boot repair

install Boot-Repair in Ubuntu

– boot your computer on a Ubuntu live-CD or live-USB.

– choose “Try Ubuntu”

– connect internet

– open a new Terminal, then type:

sudo add-apt-repository ppa:yannubuntu/boot-repair && sudo apt-get update

– Press Enter.

– Then type:

sudo apt-get install -y boot-repair && (boot-repair &)

– Press Enter