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I just installed Ubuntu 12.04.3, and afterwards Ubuntu boots perfectly (even with SecureBoot still enabled etc), however selecting Windows 8 leads to the common errors:

Secure Boot forbids loading module from (hd1,gpt6) /boot/grub/ntfs.mod
no such device 564525C65425C5233
unknown command `drivemap'
invalid EFI file path

If I use Boot-Repair to fix grub, then disable SecureBoot both OS boot. However, I'd like to know if there is a way where I can have Win 8 boot whilst leaving SecureBoot switched on for the added security benefits? I'd also like to understand better what exactly is going on here, how can it be SecureBoot causes issues for Win 8 loading here, but Ubuntu is fine..

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up vote 1 down vote accepted

Unfortunately, some versions of GRUB have problems launching the Windows boot loader with Secure Boot active. I don't know offhand if this is true of the version of GRUB installed with Ubuntu 12.04.3, but your experience suggests it is. There are at least four ways around the problem:

  • Disable Secure Boot. (I know you said you prefer to keep it active, and I respect that; but it is an option, and it's likely to be the easiest one to use.)
  • Locate a version of GRUB 2 that can launch the Windows boot loader with Secure Boot active. Unfortunately, I don't know precisely which versions will work for this. You'll also probably have to adjust the Linux Secure Boot configuration to get this to work.
  • Install my rEFInd boot manager to serve as your primary boot selector. Actually installing rEFInd is fairly easy; simply installing the Debian package will do the trick. You'll probably have to jump through some extra hoops to get it to work with Secure Boot, though.
  • Use the firmware's built-in boot manager. With most computers, hitting Esc or a function key early in the boot process brings up its own built-in boot manager. This should enable you to boot either Windows or GRUB/Linux, without using GRUB to boot Windows. Unfortunately, which key you press varies from one machine to another, the windows for getting the boot manager is usually short, and you'll always need to use that key to boot your non-default OS.

The extra Secure Boot hoops required for using rEFInd or a non-Ubuntu version of GRUB aren't really all that difficult to navigate once you understand the principles and tools involved. The pages to which I linked are long in part because they describe several different options. In brief, you may need to install a non-Ubuntu version of shim and, when it boots for the first time, use the associated MokManager program to install the Ubuntu key file (which is included in the rEFInd binary package and in an obscure Ubuntu package whose name and URL I don't recall).

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