I had a dual boot system with Ubuntu 14.04 and Windows 8.1.
After I upgraded Win to Win10, there was no GRUB entry for Ubuntu (or maybe Ubuntu was wiped, but I didn't notice...)
I searched online and used a live flash drive to do the boot repair. I typed all the commands given by the auto repair choice.
But after I reboot, it showed no operating system can be found. I can't even boot Windows. Please let me know how can I solve this.