I've been reading some other threads, especially about dual-boot installations on the Lenovo Yoga 2 Pro running windows 8.1, but I didn't seem to find quite the exact same issue. I'm admittedly a newcomer to this (my first time trying to install Ubuntu), so I'd appreciate any opportunity I can to learn more about this!
I set aside roughly 60GB for the partition and another 8 GB for the swap. I also installed grub on the /dev/sda2
partition, which is the ESP where Windows Boot Manager is also located.
I have specified that ubuntu/grub should boot first in the BIOS Boot Menu. Secure Boot and Lenovo Fast Boot are both disabled.
Everything is going fine so far. I can boot, and grub shows up, allowing me to select between Ubuntu and Windows Boot Manager. If I choose Ubuntu, I am able to get into Ubuntu, log in, etc., perfectly fine. The trouble starts when I choose to boot into Windows instead. Once I do that, and try to shutdown/restart and boot up Ubuntu, the following message appears:
Failed to open /EFI/ubuntu/grubx64.efi - Not Found
Failed to load image /EFI/ubuntu/grubx64.efi: Not Found
start_image() returned Not Found
I have verified on the Windows side that the files claimed to not exist are in fact in the specified folders. They were detected using the bcdedit /enum firmware.
I have also tried using the command
bcdedit /set {bootmgr} path \EFI\ubuntu\shimx64.efi
in the Administrator Command Prompt with no luck.
After this, I booted live from a USB and did a boot repair, which fixed GRUB... until I booted back into the Windows side again, at which point the same issue occurred.
Any help would be greatly appreciated, and I'll try to provide any other information that might be helpful. Thanks!