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I followed this Askubuntu Post to install Ubuntu as dual-boot with Windows 8.1 pre-installed as(UEFI),but I am not able to dual-boot and tried Boot-Repair

  1. I first burned an Ubuntu ISO on a blank DVD-R to create the LiveCD.
  2. Even with secure boot disabled, when I tried restarting my computer, it never booted to the installation screen, and it just skipped to Windows.
  3. After a lot of skimming, I thought I had to put my computer in Legacy Mode in order to get give my CD/ROM drive priority.
  4. I installed Ubuntu and used my existing EFI partition.
  5. Ubuntu works, but Windows doesn't, probably because my laptop is stuck in Legacy Mode.
  6. I tried switching back to UEFI using boot-repair on the Linux Terminal, and going into Advanced Properties -> Grub Location -> Ticking the checkbox for EFI, but it says I need to be in an EFI session, and now I'm just really lost and confused at what I've all done.
  7. I can see my Windows8.1 OS on a partition but I want to dual-boot Windows 8.1 along with Ubuntu?

Did I just brick my computer?

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Enabling BIOS/CSM/legacy support was a mistake. You now have Windows installed in EFI mode and Linux installed in BIOS mode. Most computers make it difficult to switch from one boot mode to the other, so such mixed-mode installations are difficult to manage.

To fix it, install an EFI boot loader for Linux. As detailed on the page to which I've just linked, several are available; but as part of the normal process of EFI boot loader installation requires that you be booted in EFI mode, you can't do this from your current Ubuntu installation -- at least, not without jumping through some extra hoops. There are several ways around this, one of which is:

  1. Download the USB flash drive or CD-R version of my rEFInd boot manager.
  2. Prepare a USB flash drive or CD-R from the downloaded image.
  3. Boot the rEFInd medium you've just prepared. This may require using your firmware's built-in boot manager or going into the setup utility and disabling BIOS/CSM/legacy support. If you use the boot manager and see two entries for your boot medium, select the one with "UEFI" in the description string.
  4. In rEFInd, you should see an entry for Windows and one or more entries to boot Linux kernels. Select one of the latter and Ubuntu should start. Note, however, that if you used a separate /boot partition, you'll need to hit F2 or Insert twice, rather than Enter, to launch Ubuntu. When you do this, a simple line editor will open, in which you must enter a root= specification pointing your kernel to your root filesystem.
  5. In Linux, install the boot loader of your choice. Two relatively easy ways to do this are:
    • Install the rEFInd Debian package or PPA, as described on the rEFInd page. This will set up rEFInd as your default boot program.
    • Run Boot Repair again. This should install the EFI version of GRUB. Note that this path leaves more to chance than the preceding one; at this point you really don't know that the way Boot Repair sets things up will work, whereas you know that rEFInd will boot Ubuntu.
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  • In my system both Windows and Ubuntu are installed as efi and I choose each one of them by pressing F9 or by default Windows boot if I don't choose anything. – Mudit Kapil Mar 16 '15 at 16:09
  • and if I don't enable legacy in BIOS then I am unable to boot Ubuntu because I don't get option to interrupt boot -process. – Mudit Kapil Mar 16 '15 at 16:15
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    This worked beautifully! I didn't have to put rEFInd Boot Manager on a liveCD or USB flash drive. I simply installed it on Ubuntu, and when I restarted my computer, I pashed F8, F9, F2 etc... to go to the boot menu, and I switched back to UEFI, and everything worked. rEFInd worked perfectly! – Richarizardd Mar 18 '15 at 1:23
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    Richarizardd, the way you installed rEFInd, it probably "hijacked" the Windows boot loader (from Ubuntu, /boot/efi/EFI/Microsoft/Boot/bootmgfw.efi). This works fine in the short term, but sooner or later Windows is likely to overwrite rEFInd with an updated version of its boot loader. Thus, you may need to fiddle with this in the future. To avoid this, you could type sudo mvrefind.sh /boot/efi/EFI/Microsoft/Boot /boot/efi/EFI/refind in Ubuntu, but there is a risk that this will derail your currently-working boot. You'll have to decide whether to risk a problem now or in the future. – Rod Smith Mar 19 '15 at 1:29
  • Reading your answers is an eye-opener! Thanks! (and upvoted!) – Fabby Mar 23 '15 at 23:16
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In EFI you normally can also edit the boot priority. If you switch from EFI in Legacy your System will crash. I had the same problem and at the end, the only thing that really helped was to reinstall both systems. The Problem ist that you had install one OS in Legacy and the other one in EFI. I dont think thats working well. So yes, I think you crashed your System

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  • I'm sorry, I don't see how this answers the question asked... – Elder Geek Mar 16 '15 at 23:24

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