1. boot into live session

2. onnect to the Internet

3. open a new Terminal, then type the following commands (press Enter after each line):

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

3. click the "Recommended repair" button. When repair is finished reboot


 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 apt-get update
sudo apt-get install -y boot-repair && boot-repair
Using Boot-Repair
Recommended repair
launch Boot-Repair from either :
the Dash (the Ubuntu logo at the top-left of the screen)
or by typing 'boot-repair' in a terminal
Then click the "Recommended repair" button. When repair is finished, note the URL (paste.ubuntu.com/XXXXX) that appeared on a paper, then reboot and check if you recovered access to your OSs.

If the repair did not succeed, indicate the URL to people who help you by email or forum.
Warning: the default settings are the ones used by the "Recommended Repair". Changing them may worsen your problem. Don't modify them before creating a BootInfo URL, and asking for advice on Ubuntu Forums Absolute Beginners Section or in Installation and Upgrades.

Advanced options
* If you would like to opt-out of the paste.ubuntu.com link creation (Not recommended for inexperienced users who are seeking help from a forum or IRC member), you can. Simple click on the Advanced Options, and find the "Other Options" tab. Uncheck "Upload the report to a pastebin".

* The log may include UUIDs, LUKS headers, hex dump of your first sectors of your drives, device serial numbers, your username and more.