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Thread: Windows 8.1/Ubuntu dual boot

  1. #1
    Join Date
    Sep 2013
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    Windows 8.1/Ubuntu dual boot

    Two days ago I installed on my notebook Windows 8.1 and Ubuntu in dual boot. This is how i partitioned my HD:



    Now from grub, booting Ubuntu gives no problems. But when I select "Windows Boot Manager" from here



    there's an error:



    Instead, selecting SYSTEM SETUP, and then Windows Boot Manager (see image below), Windows normally starts.



    Now my question is: I have done some mistakes during installation? (I don't think, I installed Ubuntu and Windows carefully and manually partitioned HD).
    It's a serious problem?
    Thank you for your support.

  2. #2
    Join Date
    Jun 2009
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    Re: Windows 8.1/Ubuntu dual boot

    Generally the efi partition should be near beginning of drive, but I guess now it is not required to be first as I have posted many times.

    Windows has very specific requirements for its partitions including order. Often easiest to just let it install first.

    Microsoft suggested partitions including reserved partition for gpt & UEFI:
    http://technet.microsoft.com/en-us/l...8WS.10%29.aspx
    Older Windows info on gpt - 2008 updated 2011
    http://msdn.microsoft.com/en-us/wind.../gg463525.aspx
    Windows technical info on gpt and GUIDs
    http://msdn.microsoft.com/library/wi...sktop/aa365449
    Order on drive is important:
    http://en.wikipedia.org/wiki/Microso...rved_Partition
    Windows 8 info
    http://technet.microsoft.com/en-us/l.../hh824947.aspx
    For info on UEFI boot install & repair - Updated Mar 2015:
    http://ubuntuforums.org/showthread.php?t=2147295
    Please use Thread Tools above first post to close thread when/if answered completely.







  3. #3
    Join Date
    Mar 2011
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    622

    Re: Windows 8.1/Ubuntu dual boot

    This is bug 1091464. Please add yourself to the "Does this affect me?" list. I have heard claims that is it possible to boot in this situation with secure boot disabled, but cannot verify that. I have this problem, and use the efi boot menu to select the non-default OS (with secure boot on).

  4. #4
    Join Date
    Sep 2013
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    7

    Re: Windows 8.1/Ubuntu dual boot

    First of all thank you both.
    I used the "Boot-repair" tool (https://help.ubuntu.com/community/Boot-Repair) and now (after having disabled secure boot) both OSs are bootable smoothly from GRUB.
    Actually GRUB list grew, as you can see:



    Now, can you explain in short what's the meaning of each line?

    And... I read some stuff around but still don't understand the exact meaning of UEFI. It's something like a BIOS? Or more like GRUB?

  5. #5
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    Re: Windows 8.1/Ubuntu dual boot

    UEFI is the new BIOS, but has an mode to work like BIOS for those who have to have compatiblity.
    UEFI Compatibility Support Module (CSM), which emulates a BIOS mode

    Apple converted to UEFI when it changed to Intel chips, but still has an older version.


    ExtremeTech article on what UEFI is, from 2011
    http://www.extremetech.com/computing...os-replacement

    It looks like boot repair ran its "buggy" UEFI rename function. I am not sure it is always required, but it is for those UEFI that internally hard code UEFI to only boot the Windows efi file. So Boot-Repair renames the Windows file and makes grub2's shim be the Windows file. The UEFI thinks it is booting Windows but is really booting grub2 and then from grub2 menu you can boot Windows.

    Then renamed /EFI/microsoft/boot/shimx64.efi to bootmgfw.efi
    Actual Windows boot file, originally bootmgfw.efi.
    /EFI/Microsoft/Boot/bkpbootmgfw.efi

    With the renamed file you cannot directly boot Windows from UEFI menu as it really is shim.

    To undo & to rename files to their original names, you just need to tick the "Restore EFI backups" option of Boot-Repair.

    Also grub2's os-prober did not used to find UEFI boot, but only BIOS boot entries. Those would not work with UEFI, so Boot-Repair added correct entries. Only the very newest version of grub creates correctly UEFI boot entry to boot Windows (but it may be shim after rename).
    For info on UEFI boot install & repair - Updated Mar 2015:
    http://ubuntuforums.org/showthread.php?t=2147295
    Please use Thread Tools above first post to close thread when/if answered completely.







  6. #6
    Join Date
    Sep 2013
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    7

    Re: Windows 8.1/Ubuntu dual boot

    Mmm well, but beyond these naming issues, now it's all ok on my notebook? These are only issues regardin booting right? Or I could have problems with OSs executions?

  7. #7
    Join Date
    Jun 2009
    Location
    Chicago Suburbs
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    Ubuntu 14.04 Trusty Tahr

    Re: Windows 8.1/Ubuntu dual boot

    Some advantage to un-renaming as then you should be able to directly boot either system from UEFI.

    Also some Windows updates may reset Windows as default boot, so you may need to change that back. Windows updates may overwrite the shim version and then you can only boot Windows. Bit more maintenance probably required, but systems both should work.
    For info on UEFI boot install & repair - Updated Mar 2015:
    http://ubuntuforums.org/showthread.php?t=2147295
    Please use Thread Tools above first post to close thread when/if answered completely.







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