I used to have two harddrives sda (Ubuntu 12.04LTS) and sdb (Window 7). I used grub2 to boot between both of them.

Then, I did a clean install of Ubuntu 13.10 on sda replacing the old Ubuntu version. I think, this install automatically changed boot to UEFI if I'm not mistaken.

Now, the Windows boot option doesn't show up anymore in grub menu and I have no way to boot into my Windows 7 installation anymore, which I need to do occassionally.

How can I restore it? Do I need to revert back to a previous boot mechanism prior UEFI (which one?)? What would be of interest to debug this?

sdb1 is the boot partition of Windows 7 (ntfs)

My Linux partitions are encrypted.

  • Your EFI-vs-BIOS configuration is not 100% clear, but the proper solution is reliant on getting this detail right. Thus, I recommend you run the Boot Info Script, post the RESULTS.txt file it generates to a pastebin site, and post the resulting URL here. That should clarify the issue and avoid dead-ends caused by people making incorrect guesses about your configuration.
    – Rod Smith
    Commented Dec 2, 2013 at 0:33

1 Answer 1


Grub2 should be able to find windows using sudo update-grub. If that does not work, maybe your partition table is damaged and you should use a livecd or a tool like super grub disk to recover it.

More info: http://ubuntuforums.org/showthread.php?t=1657134

Edit: You cannot have both OS with different boot system. If one is with EFI/UEFI, the other should be installed using the same system.

  • sudo update-grub didn't help, so I will look into the thread you linked later today. But in general, it should work that I can still use my old Windows boot-table even now grub uses the EFI stuff?
    – Sebi
    Commented Dec 1, 2013 at 12:05
  • It should work in both methods (EFI and BIOS) but the UEFI is the currently recommended method, as theorically it's better than the BIOS. I've found more information here (it's for ArchLinux, but should be very similar) Commented Dec 2, 2013 at 14:19
  • After learning a bit more... You cannot have two OS installed using different BIOS systems. Both must be in the same system (or BIOS or EFI/UEFI). Commented Jun 19, 2014 at 14:12

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