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Thread: Change a dual boot OS without messing up grub

  1. #1
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    Change a dual boot OS without messing up grub

    I have ubuntu 10.10 and 12.10 dual booting. Because 12.10 was added later it is the first entry in boot.

    Here is my disk layout



    I'd like to put a linux mint in the first partition and retain ubuntu as the first entry at boot up and remain as the default.

    Of course, keeping grub intact is of primary concern.

  2. #2
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    Re: Change a dual boot OS without messing up grub

    natchez -

    Can I ask you to install gparted partition editor, then go into that and take a screenshot of what it sees? Then post the screenie here? I'm much more accustomed to deciphering the gparted style map. The one you attached isn't familiar to me.

    It looks like sda1 is a primary partition. Then the rest of the drive is an extended partition, with another version of Ubuntu installed to sda6. Right?

    Is 10.10 in sda1? Or 12.10?

    In your previous thread, we'd talked a bit about simply removing one of the Ubuntu installs. I was concerned that would screw up GRUB. If you're going to install Mint right over the top of the older version of Ubuntu, that's a whole different thing. GRUB should see that you have another version of Linux, and configure itself correctly.

    "Should" sounds like famous last words in this case, doesn't it? As in, "gosh, that shoulda worked; now what?"

    Hopefully some other folks will weigh in on this...
    Last edited by Bartender; December 8th, 2012 at 07:35 PM.

  3. #3
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    Re: Change a dual boot OS without messing up grub

    Ubuntu installs do not let you not install grub2. About the only choice is to install to a partition (which is not recommended), just as a throw away that you will not use.
    Or you can install to the MBR and then boot into 12.10 and reinstall its grub into the MBR.

    Grub also remembers where to reinstall on major updates. So if Mint is installed to the MBR, it may automatically reinstall on an update.

    From any working install you can reinstall its boot loader into the MBR. Just first boot into it. So if booting from Mint, boot into 12.10 and run these:

    sudo grub-install /dev/sda
    sudo update-grub

    But I am not sure if that updates the setting on reinstall.

    In Mint use this to see where it will re-install:
    #To see what drive grub2 uses see this - grub-pc/install_devices:
    sudo debconf-show grub-pc
    sudo grub-probe -t device /boot/grub


    #to get grub2 to remember where to reinstall on updates:
    sudo dpkg-reconfigure grub-pc
    #Enter thru first pages,spacebar to choose/unchoose drive, enter to accept, do not choose partitions


    Someone posted that unchoosing all drives then left no reinstall choice, so grub would not get reinstalled.
    For info on UEFI boot install & repair:
    http://ubuntuforums.org/showthread.php?t=2147295
    Please use Thread Tools above first post to close thread when/if answered completely.







  4. #4
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    Re: Change a dual boot OS without messing up grub

    oldfred, you kinda lost me...

    I think what the OP has so far is a functional dual-boot with 10.10 in sda1 and 12.10 in sda6.

    And I think what he wants to do is over-write 10.10 in sda1 with Mint.

    But it might be the other way around - maybe 12.10 is in the primary partition (sda1) and 10.10 is inside the extended (sda6)

    Do you think he'd have to mess with the bootloader at all? I'm kinda sorta thinking that GRUB will just take care of things on its own.

    natchez, selecting the default OS isn't a big deal. As you say, a functional GRUB is the highest priority. We can switch the default OS later if necessary. If we don't get a definitive answer on this soon, maybe I'll just simulate your setup on a spare PC and see what happens.
    Last edited by Bartender; December 8th, 2012 at 07:37 PM.

  5. #5
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    Re: Change a dual boot OS without messing up grub

    I have not installed Linux mint but my guess would be that as it is installing last it will put its boot loader into the MBR and so Mint will be at the top of the list. But if the OP does what oldfred says, boot into 12.10 and run

    sudo update-grub
    And then

    sudo grub-install /dev/sda
    That will put the 12.10 version of Grub back into the MBR and the first OS in the list will be Ubuntu.

    This is how I do it.

    Regards.
    It is a machine. It is more stupid than we are. It will not stop us from doing stupid things.
    Ubuntu user #33,200. Linux user #530,530


  6. #6
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    Re: Change a dual boot OS without messing up grub

    I'm about to demonstrate why I posted in the Absolute Beginners section.

    There are a lot of things about linux that give me the cold robies, make my teeth hurt, one of them is (the dreaded) grub. With windows it was the mbr. Every time I have fooled with them I ended up formating and reinstalling.

    I was going to put mint in place of 10.10 because the space was there. I've got PLENTY of space for 12.10 on the partition as I have never used even 35 gigs even with those bloated windows thingees.

    Thank you for your respnses but I'll leave well enough alone.

    FYI - 12.10 is in partition 2
    Last edited by natchezjohn; December 8th, 2012 at 08:15 PM.

  7. #7
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    Re: Change a dual boot OS without messing up grub

    On the other hand Bartender if you DO go through the trouble of setting it up on another pc. I'll follow your lead.

  8. #8
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    Re: Change a dual boot OS without messing up grub

    If I understand what you want to do correctly...

    Boot into a linux mint live CD, install it onto the partition you want to install it on (/dev/sda1?). Remember to tick the option to format the partition (keep it as Ext4 though). Give it a / mount point. To keep grub functional, install it on /dev/sda (you'll find this option where you select the partition for linux mint to install on.

    So, you have now selected linux mint to be installed on the partition you want it on, and selected grub to be installed on /dev/sda. This should do what you want, so continue with he installation and you should be sweet.
    Last edited by debodas; December 8th, 2012 at 11:58 PM. Reason: spelling

  9. #9
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    Re: Change a dual boot OS without messing up grub

    Oh! and you asked for a gparted shot. Here it is


  10. #10
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    Re: Change a dual boot OS without messing up grub

    Quote Originally Posted by kingnick42 View Post
    If I understand what you want to do correctly...

    Boot into a linux mint live CD, install in onto the partition you want to install in on (/dev/sda1?). Remember to tick the option to format the partition (keep it as Ext4 though). Give it a / mount point. To keep grub functional, install it on /dev/sda (you'll find this option where you select the partition for linux mint to install on.

    So, you have now selected linux mint to be installed on the partition you want it on, and selected grub to be installed on /dev/sda. This should do what you want, so continue with he installation and you should be sweet.
    Kingnick - YOU tempt me. Rational, precise, within my (limited) capabilities.

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