Comment 630 for bug 1734147

To fix the issue if you lost access to all operating systems on your machine:

Using Virtualbox in any Windows/Linux machine, create a regular installation of Ubuntu on a flash drive (16GB or more space), since you can't create an installation on your hard drive due to problems in the kernel. If you install Ubuntu on the flash drive, you also install the bootloader into the flash drive. (Notice the "Device for Bootloader installation" during the installation process).

Reboot, you should see the new entry for the operating system on the flash drive. Now proceed to download the updated kernel as described in the bug description. That would fix the issue.