I have a Sony laptop with UEFI, SecureBoot and Windows 8. I read Ubuntu UEFI recommendations, then freed some 35 gb on system hdd and installed Ubuntu 13.04 64 bit in EFI mode, keeping Windows 8. After succesfull install, system booted into Windows 8 only, and I used Boot-Repair as recommended. Boot-Repair said that all is ok and here is his log: http://paste.ubuntu.com/6061646 But now system can not boot totally. Only thing I see is "Secure Boot Failed/Operating System is Invalid" What can I do next to repair Ubuntu and Windows boot?
The easiest solution is likely to be to disable Secure Boot. Unfortunately, details of how to do this vary from one computer to another, but all x86-64-based PCs that ship with Windows 8 should give you some means to do that.
If you want to keep Secure Boot active, my advice is to upgrade your Secure Boot software; the last I checked, Ubuntu was still using shim version 0.1, whereas the latest available in signed form is version 0.4 (AFAIK, available only as a Fedora package). Even version 0.2 (available from Fedora, OpenSUSE, and Matthew Garrett) is better than version 0.1. See here for a fuller description of how to install shim "from scratch." (Unfortunately, the process is rather involved.) There's also the possibility of switching to PreLoader, which is easier to install and configure than shim, but more limiting in various ways.