I have installed Win8 and Ubuntu side by side before in the past and had issues with booting which were fixed perfectly the first time using boot-repair. This time, I installed Win8.1 and Ubuntu with the same issue. Boot-repair also fixed it. After running Windows a few times, I attempted to reboot and got the following:
Error: Unknown Filesystem grub rescue>
I was able to find the windows UEFI boot file doing a boot options from the BIOS and successfully boot Win8 from:
MS/Boot/bootmgrfw.efi. When I booted into Ubuntu Live from a USB and reinstalled and re-ran boot-repair, it was much more involved and asked me to open a couple of terminal windows and paste in some additional commands. At the end running, it said everything was good but I still have the same issues. It appears it made backup copies of my UEFI boot files because now I need to boot
bkpbootmgrfw.efi to successfully load Win8.1 while
bootmgrfw.efi gives the same unknown filesystem error.
The URL I got after running boot-repair the second time is http://paste.ubuntu.com/6514148/ Is there a way to manually fix the UEFI boot or should I blow away UBUNTU, repair Windows and then reinstall UBUNTU ?
Update: I can boot
\efi\ubuntu\grub64.efi and get to the normal grub boot menu which I can load either Win8 or Ubuntu. It also shows the boot file for Win8 to be the backup file.