When it first appeared, UEFI secure boot was going to be doom for free operating systems:
but it turned out to be easier than predicted to get Microsoft to sign things:
So now, in theory, it’s possible to have Secure UEFI enabled devices dual boot Windows and another operating system.
Indeed Ubuntu now transparently support this in Ubuntu 15.04 .
Of course, it’s never that easy. We just tried to make this work on a newly purchased Lenovo Thinkpad Yoga device, and it’s sort of there, but involves a horrible kludge.
Specifically, when Ubuntu is installed, it does everything you want it to (shrinks the Windows partition, installs itself in the freed space), and then installs its own EFI boot loader, and sets this as the default EFI boot loader; it also creates a grub configuration that includes a “Windows” entry that should make its EFI boot loader find and load the Windows EFI boot manager.
Rebooting into ubuntu works perfectly.
If however, you select “Windows” in the grub menu, the EFI boot loader complaints that it cannot load
/ACPI(a0341d0,0)/PCI(2,1f)/Sata(0,0,0)/HD(2,1f4800,82000,7907c175f283a74e,2,2)/File(\EFI\Microsoft\Boot)/File(bootmgfw.efi)/EndEntire
Fortunately, if you “ESC” to the grub prompt, and then type “exit” at that prompt, Lenovo’s UEFI implementation notices that the grub EFI loader has quit, and pops up a menu allowing you to select from available EFI boot loaders, including the Windows one. So booting into windows becomes a case of ↓, ↓, ↵, <ESC>, “exit”,↓, ↵ …
If I boot ubuntu, and look in /boot/efi, there is a file /boot/efi/EFI/Microsoft/Boot/bootmgfw.efi , so I’m not sure if the problem is in the somewhat convoluted representation of where to find the /boot/efi partition that grub has invented there, perhaps?
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