Windows 8 doesn't show in GRUB 2, Bootrepair didn't help

Question

I've spend the entire day on this problem, probably because I'm relatively new to Ubuntu.

I installed Windows 8.1 after Ubuntu. First I wasn't able to start Ubuntu, but after Bootrepair I was. Unfortunately I just changed the problem, since now I'm not able to boot Windows. The following link is of the Bootrepair report: http://paste.ubuntu.com/10971525/ .

Windows 8 is not installed on the first hd and according to some that is a problem, see: http://www.gnu.org/software/grub/manual/grub.html#DOS_002fWindows . It say's something about disk swapping. Should I try that or is there a different solution?

Answer 1

Your Windows on sda, uses MBR(msdos) so Windows can only boot in CSM mode. CSM - UEFI Compatibility Support Module (CSM), which emulates a BIOS mode. And Ubuntu is on sdb in UEFI boot mode. UEFI & CSM are not compatible or you have to totally reboot to change from one system to the other and may have to change UEFI settings turning on UEFI or off CSM or vice versa. Better to have all systems in same boot mode.

To restore Windows boot in BIOS mode, you must install a Windows boot loader to the MBR of sda. Your Windows repair flash drive can do that or use Advanced mode in Boot-Repair. And then turn on CSM mode in UEFI to boot Windows.

You can use Boot-Repair to convert Ubuntu 's install from UEFI to BIOS, but be sure to only install grub to drive that is sdb not all drives like the default autofix in Boot-Repair. To boot in CSM mode you also must turn off secure boot in UEFI.

You do show grub installed to the MBR of sdb for BIOS boot, but fstab still shows mounting of efi partition for UEFI boot updates. So at some point you may have had BIOS boot on sdb?

Answer 2

You can try to add a windows entry in grub. Open /etc/grub.d/40_custom file and add the following entry by substituting the details to suit your installation:

menuentry "Windows 8" {
    set root='(hd0,gpt1)'
    chainloader /EFI/microsoft/BOOT/bootmgfw.efi
}

Then run update-grub and hopefully you'll see an entry in grub.

Answer 3

Thanks for your thorough responses. I'll try those tomorrow (hours of fiddling with Grub got the best of me).

In the mean-time I found a less ideal solution: in the CLI of GRUB I type:

chainloader (hd0,1)+1
boot

That were the commands to start Windows. It isn't as convenient as the normal way, but I settle for that at the moment. There must be a way to put those commands in the configuration file... Maybe oldfreds method...