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Thread: Trouble dual booting 12.2 and Windows 7 on EFI enabled system

  1. #31
    Join Date
    Sep 2012
    Posts
    4,977

    Default Re: Trouble dual booting 12.2 and Windows 7 on EFI enabled system

    I mean that in your example last sector of partition is 4294967295 == 0xffffffff.
    and where did you read this info?
    Which one? Partition layout - in your article, Protective MBR layout - in UEFI specification and parted behavior - in parted source code ...

  2. #32

    Default Re: Trouble dual booting 12.2 and Windows 7 on EFI enabled system

    I have read the please_try_again article about 12.1, but I hoped this issue would be solved in the 12.2 release ...

  3. #33

    Default Re: Trouble dual booting 12.2 and Windows 7 on EFI enabled system

    Quote Originally Posted by arvidjaar View Post
    I mean that in your example last sector of partition is 4294967295 == 0xffffffff.
    OK, I understand. Yes, that's true ... and weird somehow. The protective MBR was created by Windows after I wiped out the first track before installing. See the last example in my article: same thing with another disk (SSD 120 GB). It looks like Windows would just use 0xffffffff as the end sector of any protective partition, no matter its size.

    I will try to get access to this computer today. It actually has 2 SSDs and the one where Linux is installed hasn't been touched by Windows.

  4. #34

    Default Re: Trouble dual booting 12.2 and Windows 7 on EFI enabled system

    I wonder what Windows would do if you replace 0xffffffff with the effective last sector. This is the kind of trick that could work after all. Then the protective MBR would meet the specs and openSUSE wouldn't/shouldn't create a hybrid MBR. Anyone wants to try that?

  5. #35

    Default Re: Trouble dual booting 12.2 and Windows 7 on EFI enabled system

    @arvidjaar,

    I think you're going to like this:

    Code:
    # fdisk -l
    
    WARNING: GPT (GUID Partition Table) detected on '/dev/sda'! The util fdisk doesn't support GPT. Use GNU Parted.
    
    
    Disk /dev/sda: 120.0 GB, 120034123776 bytes
    256 heads, 63 sectors/track, 14536 cylinders, total 234441648 sectors
    Units = sectors of 1 * 512 = 512 bytes
    Sector size (logical/physical): 512 bytes / 512 bytes
    I/O size (minimum/optimal): 512 bytes / 512 bytes
    Disk identifier: 0x9080940a
    
       Device Boot      Start         End      Blocks   Id  System
    /dev/sda1               1  4294967295  2147483647+  ee  GPT
    
    WARNING: GPT (GUID Partition Table) detected on '/dev/sdb'! The util fdisk doesn't support GPT. Use GNU Parted.
    
    
    Disk /dev/sdb: 120.0 GB, 120034123776 bytes
    255 heads, 63 sectors/track, 14593 cylinders, total 234441648 sectors
    Units = sectors of 1 * 512 = 512 bytes
    Sector size (logical/physical): 512 bytes / 512 bytes
    I/O size (minimum/optimal): 512 bytes / 512 bytes
    Disk identifier: 0x00000000
    
       Device Boot      Start         End      Blocks   Id  System
    /dev/sdb1               1   234441647   117220823+  ee  GPT
    I guess I don't need to tell you which one is Windows.

  6. #36

    Default Re: Trouble dual booting 12.2 and Windows 7 on EFI enabled system

    Quote Originally Posted by arvidjaar View Post
    I begin to suspect what happens. openSUSE has parted patches to support Hybrid MBR. With these patches parted assumes that GPT disk has Hybrid MBR if it does not have valid Protective MBR
    So it's not a bug. It's a feature.

  7. #37
    Join Date
    Sep 2012
    Posts
    4,977

    Default Re: Trouble dual booting 12.2 and Windows 7 on EFI enabled system

    Well ... this feature makes Windows unbootable ...

    I have patched parted to accept protective MBR with size set to 0xFFFFFFFF. But it still rewrites PMBR to be correct (i.e. after you create any partition it will change 0xFFFFFFFF => 234441647 in your example). This still may break Windows, although in this case any distribution using parted would have the same issue. So I really need someone to verify that Windows tolerates corrected PMBR before submitting fix. This could also be tested by

    - installing Windows on drive leaving space
    - creating partition on this drive under Linux, e.g. using live CD (ideally using vanilla parted, may Parted Magic)
    - testing if Windows still boots

    As this requires system with UEFI firmware, I am unable to do it myself. Unless UEFI can be emulated in KVM or VMware ... anyone knows for sure?

  8. #38

    Default Re: Trouble dual booting 12.2 and Windows 7 on EFI enabled system

    Quote Originally Posted by arvidjaar View Post
    As this requires system with UEFI firmware, I am unable to do it myself. Unless UEFI can be emulated in KVM or VMware ... anyone knows for sure?
    VIrtualBox can emulate EFI out of the box. I never tested it though.

  9. #39

    Default Re: Trouble dual booting 12.2 and Windows 7 on EFI enabled system

    Quote Originally Posted by arvidjaar View Post

    So I really need someone to verify that Windows tolerates corrected PMBR before submitting fix. This could also be tested by

    - installing Windows on drive leaving space
    - creating partition on this drive under Linux, e.g. using live CD (ideally using vanilla parted, may Parted Magic)
    - testing if Windows still boots
    Also gdisk has options to
    • backup/restore the protective MBR and GPT headers
    • create a new protective MBR

      Quote Originally Posted by man gdisk
      n Create a new protective MBR. Use this option if the current protective MBR is damaged in a way that gdisk
      doesn't automatically detect and correct, or if you want to convert a hybrid MBR into a "pure" GPT with a
      conventional protective MBR.


    Maybe one could just boot a linux live CD on a WIndows UEFI machine, install gdisk if it's not already there, backup the MBR + GPT, create a new ('correct') protective MBR, see if WIndows still boots.

  10. #40

    Default Re: Trouble dual booting 12.2 and Windows 7 on EFI enabled system

    I will try that test, loading windows and then booting a live cd to add a partition, and see how win7 handles it. But I can't do it until Monday. I appreciate all the good advice and info that I've seen here, and I neglected to thank y'all in my previous post. Thank you all.

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