This question already has an answer here:
(The original title of this post was "Boot Repair doesn't work after April 2014 Windows 8.1 Update" since I wanted to highlight that this is not about the 8.0 -> 8.1 update, but the update for 8.1 that came out in April 2014.)
I'm dual booting Ubuntu 13.10 and Windows 8.1. Today I got the "big" Windows 8.1 Update and now my PC doesn't show GRUB anymore, but boots straight into Windows. I've tried running Boot Repair from Ubuntu on a USB stick, but that doesn't seem to do anything. The system still boots directly into Windows every time.
I'm sure I just need to change some setting in Boot Repair, but I don't want to do that without knowing what I'm doing. :)
Here's my Boot Repair Ubuntu Pastebin thingy:
Now I effed everything up completely.
Since I didn't get an answer here, I tried fiddeling with the Boot Repair options. Now the following message flashes for a second when I start the PC:
Could not open "\EFI\BOOT\fallback.efi": 14 Failed to open \EFI\BOOT\grubx64.efi - 800000000000000E Failed to load image Failed to open \EFI\BOOT\MokManager.efi - 800000000000000E Failed to load image
...just before stopping at this line:
Operating System Not Found
Here's my updated Boot Repair report: http://paste.ubuntu.com/7233853/