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Thread: HOWTO: Restore GRUB (if your MBR is messed up)

  1. #101
    Join Date
    Aug 2006
    Beans
    4

    Re: HOWTO: Restore GRUB (if your MBR is messed up)

    Quote Originally Posted by ucsdrake View Post
    you go from
    grub> root (hd0,1)
    to
    grub> setup (hd0)

    from my understanding the ,1 was avery important part of this fix ... do we need to add the ,1 or not?

    sorry i just want to make sure i get all the steps right before i go forward seeing as i'm having problems as it is and i dont want to make it worse lol
    ucsdrake,
    I can't see any typos in what I wrote and it worked for my amd64 3500+ installation of 6.10.

    I can't say more then that. Now I just need to solve my wireless problems...

  2. #102
    Join Date
    Jul 2006
    Location
    Liguria, Italy
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    117
    Distro
    Ubuntu 10.04 Lucid Lynx

    Lightbulb Re: HOWTO: Restore GRUB (if your MBR is messed up)

    hi this can help anybody...

    I substituted my HD with a larger one and used partimage to move linux partition to the new HD... but I had a continuos Grub Error 15 at boot (without any specified "file not found").

    I tried to do anything suggested in this thread but i kept having this problem.

    Then i understood it was a BIOS problem. In fact my bios allowes to select a priority in HD booting access. Even if i moved my last HD from master to slave it still was at the top of the bios hd boot priority.

    So i changed properly this value and finally the correct grub has loaded.

    hth

    bye
    sblanzio

  3. #103
    Join Date
    Aug 2006
    Location
    Slovakia
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    41

    Re: HOWTO: Restore GRUB (if your MBR is messed up)

    This guide sure helped a lot of people I just messed with partitions a little bit so my grub did not boot. Solution? Fire up LiveCD, use Konqueror to Google "Ubuntu howto restore GRUB" and the solution is right there. I have to love this ! Thumbs up

  4. #104
    Join Date
    Aug 2006
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    99
    Distro
    Ubuntu 6.10 Edgy

    Re: HOWTO: Restore GRUB (if your MBR is messed up)

    The screen freezes at the splash screen.

  5. #105
    Join Date
    Aug 2006
    Beans
    99
    Distro
    Ubuntu 6.10 Edgy

    Re: HOWTO: Restore GRUB (if your MBR is messed up)

    and when I use the method in the first post there is never a root file system. see screenshot.
    Attached Images Attached Images

  6. #106
    Join Date
    May 2006
    Location
    United Kingdom
    Beans
    469
    Distro
    Ubuntu 11.04 Natty Narwhal

    Re: HOWTO: Restore GRUB (if your MBR is messed up)

    Has anyone had problems using SATA drives in conjunction with IDE (PATA) drives? I ask this as I have had to physically unplug the power to any IDE drives otherwise GRUB installs to the MBR of the IDE drive. Have had this happen on all my machines so isn't a one off.


  7. #107
    Join Date
    Dec 2006
    Location
    Los Angeles, CA
    Beans
    13
    Distro
    Ubuntu 10.04 Lucid Lynx

    Re: HOWTO: Restore GRUB (if your MBR is messed up)

    OK, so here's my problem. I'm running a dual boot with Edgy and Windows XP. Recently I started having all sorts of trouble with getting GRUB to boot properly, and I eventually resorted to popping in the Windows XP CD and restoring the MBR from there. Now Windows works fine, but it bypasses GRUB entirely and I can't figure out how to get back to Ubuntu.

    I've looked at a lot of the solutions offered here, and they all seem to involve booting from the linux CD. But for some insane reason which I still can't figure out, my CD drive will read practically any disc except the Ubuntu disc. (I've tried burning multiple copies from multiple computers. None of them work, so I'm quite sure it's a problem with my drive.) Can anyone help me restore GRUB without the use of a CD?

  8. #108
    Join Date
    Dec 2006
    Location
    San Antonio, TX
    Beans
    50
    Distro
    Ubuntu Development Release

    Re: HOWTO: Restore GRUB (if your MBR is messed up)

    Ok I am trying to get triple boot working. I was running XP and xubuntu. I installed ubuntu and the xubuntu dissapeared off my grub, how do I add xubuntu back to grub or edit the grub menu? FYI xp is hd0, xubuntu is hd4 and ubuntu is hd5
    when I put in the command " find /boot/grub/stage1 " the output is " (hd0,5)"
    thanks in advance!

  9. #109
    Join Date
    Mar 2007
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    Hidden!

    Re: HOWTO: Restore GRUB (if your MBR is messed up)

    I have been trying for a WEEK without any remote sniff of success to fix GRUB.
    My setup:

    Hda = WIndows XP. Master on IDE0 (Work drive)
    Hdd = Windows XP. Slave on IDE1 (Occasional backup drive that I now wanted to remove)
    Sda = Ubuntu Edgy on S-Ata (Hopefully new work drive)

    The problem:
    Installed Edgy with all drives in the machine, removing the hdd cause GRUB error21 in Stage 1.5

    I finally fixed the problem after thinking about it for a while and trying out some things.

    There are 2 files in /boot/grub. device.map and menu.lst that make a difference. Basically they tell what shows up on the GRUB menu on bootup it seems.

    steps:

    1: Remove Hdd
    2: Boot using Ubuntu Edgy install CD
    3: Mount the Edgy drive as explained earlier like this:

    In the install CD gui open a terminal or use ctrl+alt+f1 for a different term.
    Changes as root user!

    > sudo bash """switch to root user"""
    > mkdir ubuntumnt """make a mount point"""
    > mount -t ext3 /dev/sda1 ubuntumnt """Mount ubuntu drive. the '1' is a partition (s-ata drive, partition 1). In other words, mount the partition, not the drive"""

    4: Now that you have a point edit the device.map and menu/lst files

    > vi ubuntumnt/boot/grub/device.map
    """This shows the contents of the device.map file"""
    hd0 /dev/hda
    hd1 /dev/hdd
    hd2 /dev/sda

    """
    Edit above to remove the hdd. Since the IDE drive is read first by the system, by observation the s-ata drive will be hd(x) where x is the number after all ide drives (it seems to me), so 4 ides and an s-ata will result in hd4 being the sata drive.
    Now we have:
    """


    hd0 /dev/hda
    hd1 /dev/sda

    """save the file and edit the menu.lst""
    > vi ubuntumnt/boot/grub/menu.lst

    """At the bottom you will have entries like this"""

    ************************************************** *********************
    ## ## End Default Options ##

    title Ubuntu, kernel 2.6.17-10-generic
    root (hd2,1)
    kernel /boot/vmlinuz-2.6.17-10-generic root=/dev/hda2 ro quiet splash
    initrd /boot/initrd.img-2.6.17-10-generic
    quiet
    savedefault
    boot

    title Ubuntu, kernel 2.6.17-10-generic (recovery mode)
    root (hd2,1)
    kernel /boot/vmlinuz-2.6.17-10-generic root=/dev/hda2 ro single
    initrd /boot/initrd.img-2.6.17-10-generic
    boot

    title Ubuntu, memtest86+
    root (hd2,1)
    kernel /boot/memtest86+.bin
    quiet
    boot

    ### END DEBIAN AUTOMAGIC KERNELS LIST

    # This is a divider, added to separate the menu items below from the Debian
    # ones.
    title Other operating systems:
    root


    # This entry automatically added by the Debian installer for a non-linux OS
    # on /dev/hda1
    title Microsoft Windows XP Home Edition
    root (hd0,0)
    savedefault
    makeactive
    chainloader +1

    # This entry automatically added by the Debian installer for a non-linux OS
    # on /dev/hdd1
    title Microsoft Windows XP Home Edition
    root (hd1,0)
    savedefault
    makeactive
    chainloader +1

    ************************************************** *******************************

    """Edit the file to change the drive numbers to correspond to the device.map and remove the hdd so it now look slike this:
    ## ## End Default Options ##

    title Ubuntu, kernel 2.6.17-10-generic
    root (hd1,1)
    kernel /boot/vmlinuz-2.6.17-10-generic root=/dev/hda2 ro quiet splash
    initrd /boot/initrd.img-2.6.17-10-generic
    quiet
    savedefault
    boot

    title Ubuntu, kernel 2.6.17-10-generic (recovery mode)
    root (hd1,1)
    kernel /boot/vmlinuz-2.6.17-10-generic root=/dev/hda2 ro single
    initrd /boot/initrd.img-2.6.17-10-generic
    boot

    title Ubuntu, memtest86+
    root (hd1,1)
    kernel /boot/memtest86+.bin
    quiet
    boot

    ### END DEBIAN AUTOMAGIC KERNELS LIST

    # This is a divider, added to separate the menu items below from the Debian
    # ones.
    title Other operating systems:
    root


    # This entry automatically added by the Debian installer for a non-linux OS
    # on /dev/hda1
    title Microsoft Windows XP Home Edition
    root (hd0,0)
    savedefault
    makeactive
    chainloader +1

    ************************************************** *******************************
    """Save the file and enter the grub interface"""

    > grub

    Now we show where the root is. Since we mounted the edgy partition, we can see the grub folder. (Not mounting is the reason why "find /boot/grub/stage1" sometimes does not work as asked in above posts.
    >find /boot/grub/stage1
    hd (1,0) """This should be you edgy drive. In my case hd(1,0) after I removed hdd. 2nd Physical drive 2, partition 1. Meaning sda1 in my case"""

    Now we follow previous steps in this HOW TO
    root (hd1,0) """Define the root partition on the drive
    setup (hd1) """Setup grub on the drive"""

    """At this point all previous posts said quit and restart, yet I still got the Error21. I eventually decided the MBR on the hda windows disk was messed up too.
    Since I know the windows drive is hd0 I also did"""

    setup (hd0)
    quit

    """Now we restart the machine and voila! IT works again
    Last edited by irrational_e; March 7th, 2007 at 03:20 PM. Reason: problem solved

  10. #110
    Join Date
    Mar 2007
    Location
    New Mexico, USA
    Beans
    Hidden!
    Distro
    Kubuntu 8.04 Hardy Heron

    Re: HOWTO: Restore GRUB (if your MBR is messed up)

    avoid? hell, for a newbie prior to actually being booted into whatever distro, commandline is virtually impossible, it's plain wilderness stuff.
    New Mexico, USA - "Atlas Shrugged"

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