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Grub Fails to Recognize Windows on Separate Disk

asked 2014-03-30 12:36:28 -0500

viatorci gravatar image

updated 2014-03-30 23:59:08 -0500

I recently installed Fedora 20 on a new SSD in a Windows 8.1 system (custom built as 7, since upgraded). I set the fedora drive (/dev/sda) to boot by default in bios and I get to GRUB and Fedora no problem. The problem is I can't get GRUB to add my windows install (/dev/sdd) to the boot entry menu. There are two other media disks in between these two (sdb and sdc).

I've tried manually adding a 40_custom entry with a variety of syntaxes but boiling down more or less to:

menuentry "Windows 8.1" {
set root='hd3,msdos1'
chainloader +1

And then updating grub.cfg with grub2-mkconfig -o /boot/grub2/grub.cfg. I've also tried 'hd3, gpt1' as well as some other methods. The custom entry never even shows up in the GRUB menu (though it is in grub.cfg) so I'm not sure if that may be the problem instead.

The disk (/dev/sdd) does have a boot flag (confirmed in gparted) and will boot just fine if I enter GRUB command line and simply exit. I've run bootrec.exe /fixmbr and bootrec.exe /fixboot in Windows as well to ensure the problem is not on that end.

Interestingly it seems that Fedora is booting via EFI while Windows is not. I'm not certain if this is the case (not sure how to confirm), but it may be. Could this be exacerbating issues?

Bear with me, my linux experience is not very deep so explicit instructions are very appreciated!

EDIT: Output of parted -l : Windows install is on ATA M4-CT128M4SSD2

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answered 2019-04-09 05:05:40 -0500

This thing is more complicated than writing an admission essay. Here is my solution:

Boot Fedora and mount your Windows partition (simply open the disk on Nautilus)

Run the following on the command line (Ctrl+Alt+t):

sudo os-prober

If your Windows installation was found, you can run:

sudo update-grub

Note that step 2 is just for your convenience. You could just mount the Windows 7 partition and then run update-grub.

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Asked: 2014-03-30 12:36:28 -0500

Seen: 1,764 times

Last updated: Mar 30 '14