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Thread: Setting which partition grub looks for boot MacPro

  1. #1
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    Setting which partition grub looks for boot MacPro

    Hi all,

    I've put myself in a bit of a pickle when trying to upgrade my OS from 10.04 to 12.04. I have gotten myself part of the way out but need some additional help.

    My machine is a MacPro and so it uses an older form of EFI (instead of BIOS).

    Here's my problem. Grub looks at the wrong partition for the core.img (/dev/sda9 instead of /dev/sda2). How to I reset the MBR so that grub looks in the proper place?

    Results from boot-repair can be found at:
    (beware it's a bit of a mess).

  2. #2
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    Re: Setting which partition grub looks for boot

    I do not know Macs.

    But it looks like you have a hybrid MBR/gpt configuration. Macs do that for Windows but you do not have to for Linux.

    http://www.rodsbooks.com/gdisk/hybrid.html
    http://www.rodsbooks.com/gdisk/booting.html
    For more info on UEFI boot install & repair - Regularly Updated :
    http://ubuntuforums.org/showthread.php?t=2147295
    Please use Thread Tools above first post to change to [Solved] when/if answered completely.

  3. #3
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    Re: Setting which partition grub looks for boot

    Hi Oldfred,

    Thanks for the info. I looked over it, but it is largely greek to me. I do recall using rEFIt when I was doing the original install of Ubuntu 4 years ago.

    I'm going to see if I can make sense of this documentation, but I'm really hoping someone out there wiht knowledge of Macs will chime in.

    Mike

  4. #4
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    Re: Setting which partition grub looks for boot Macbook Pro

    Moved you to the Apple sub-forum and put Macbook in the title so you may attract someone with a Mac to help.

    Update to MacPro
    Fixed title
    Last edited by oldfred; October 29th, 2012 at 06:59 PM.
    For more info on UEFI boot install & repair - Regularly Updated :
    http://ubuntuforums.org/showthread.php?t=2147295
    Please use Thread Tools above first post to change to [Solved] when/if answered completely.

  5. #5
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    Re: Setting which partition grub looks for boot Macbook Pro

    Thanks Oldfred,

    Just to be clear it's a MacPro, not a MacBookPro.

  6. #6
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    Re: Setting which partition grub looks for boot MacPro

    Hello
    it's a Mac hardware, but you don't seem to have any MacOS on it, do you?

  7. #7
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    Re: Setting which partition grub looks for boot MacPro

    You have 3 Ubuntu systems (sda3, sda7, sda9).

    If you want your main system to be sda7 (the 12.04.1 with 3.5 kernel), and use sda2 as separate boot, just:
    1) run Boot-Repair --> Advanced options
    2) In the "GRUB location" tab, untick "Separate /boot/efi", and tick "Separate /boot: sda2"
    3) Apply
    4) indicate the new URL that will appear.

  8. #8
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    Re: Setting which partition grub looks for boot MacPro

    Hi YannaBuntu,

    Thanks for the help and yep, I only have Ubuntu installed on this machine.

    I tried doing what you suggested with boot-repair. I was able untick "Separate /boot/efi". I could not change the box for "Separate /boot" since it was 'greyed out', but it was checked and set to sda2.

    However, when I tried to apply these changes I got the following message.

    GPT detected. Please create a BIOS-Boot partition (>1MB, unformatted filesystem, bios_grub flag). This can be performed via tools such as Gparted. Then try again.
    Alternatively, you can retry after activating the [Separate /boot/efi partition:] option.

    So I used gparted and created such a partition and then reran boot-repair which had me install and reinstall some grub-pc packages and said it was fixed.

    The url with the results are at: http://paste.ubuntu.com/1318414/

    It seems like Grub is pointed to the right place now, though I'm confused a bit by what bios_boot partition that boot-repair had me make is doing.

    Dare I resetart this sucker?
    Mike

  9. #9
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    Re: Setting which partition grub looks for boot MacPro

    Not sure, gpt partitioning has a protective MBR and you have installed grub to the MBR. But with GPT there is not space after MBR for the rest of grub or core.img.

    But does a MacPro let you boot from MBR? Or do you have to go thru its efi partition which is somewhat UEFIi v1 and somewhat UEFI v2. But both Windows and Ubuntu only truly work with UEFI v2 full implementations.
    For more info on UEFI boot install & repair - Regularly Updated :
    http://ubuntuforums.org/showthread.php?t=2147295
    Please use Thread Tools above first post to change to [Solved] when/if answered completely.

  10. #10
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    Arrow Re: Setting which partition grub looks for boot MacPro

    Quote Originally Posted by mike-g2 View Post
    The url with the results are at: http://paste.ubuntu.com/1318414/
    As Oldfred said, GRUB2 needs a BIOS-Boot partition to be installed on a GPT disk. You did it correctly, so everything looks ok now.

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