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  1. #1
    Unable to dual-boot Mac OSX an Ubuntu
    Hi,

    I am trying to create a dual-boot setup on a MacBookPro 5,4 with OS X 10.6.7 and Ubuntu 10.04LTS 64bit.

    I installed rEFIt and and used Disk Utility to create a free space after the Mac HFS+ partition. Then in the Ubuntu installer, using GParted I created an ext4 partition for Linux and a Linux-swap partition. I asked the installer to put the boot loader in the Linux partition. Everything run smoothly but when trying to boot the Linux OS I get a black screen with a blinking cursor.

    This is the partition info from Mac's Partition Inspector :


    *** Report for internal hard disk ***

    Current GPT partition table:
    # Start LBA End LBA Type
    1 40 409639 EFI System (FAT)
    2 409640 430097143 Mac OS X HFS+
    3 430097144 608349419 Basic Data
    4 608349420 625137344 Linux Swap

    Current MBR partition table:
    # A Start LBA End LBA Type
    1 1 409639 ee EFI Protective
    2 * 409640 430097143 af Mac OS X HFS+
    3 430097144 608349419 83 Linux
    4 608349420 625137344 82 Linux swap / Solaris

    MBR contents:
    Boot Code: GRUB

    Partition at LBA 40:
    Boot Code: None (Non-system disk message)
    File System: FAT32
    Listed in GPT as partition 1, type EFI System (FAT)

    Partition at LBA 409640:
    Boot Code: None
    File System: HFS Extended (HFS+)
    Listed in GPT as partition 2, type Mac OS X HFS+
    Listed in MBR as partition 2, type af Mac OS X HFS+, active

    Partition at LBA 430097144:
    Boot Code: GRUB
    File System: ext4
    Listed in GPT as partition 3, type Basic Data
    Listed in MBR as partition 3, type 83 Linux

    Partition at LBA 608349420:
    Boot Code: None
    File System: Unknown
    Listed in GPT as partition 4, type Linux Swap
    Listed in MBR as partition 4, type 82 Linux swap / Solaris


    I tried booting with rEFIt as well as by pressing the 'alt' key during the start up. Same result.

    Can someone help me understand what is the meaning of : 'MBR contents: Boot Code: GRUB'

    I could understand : 'Partition at LBA 430097144: Boot Code: GRUB' - that is the Linux partition where I told the installer to put the boot loader, but what is the other one ?

    Even before installing Ubuntu rEFIt was giving me 2 options : 'Mac OS' and 'Linux HD'.
    After installing Ubuntu (in the newly created /dev/sda3 partition) rEFIt gives me 3 options : 'Mac OS', 'Linux HD' and 'Linux from partition 3' !

    Looks like no matter what, as soon as I install rEFIt i get a bogus 'Linux HD' option and somehow it prevents the real one 'Linux from partition 3' to work.

    Can't figure out what's going on ... help please.

  2. #2
    Unable to dual-boot Mac OSX an Ubuntu
    chscag's Avatar
    Member Since
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    Remove rEFIt and try booting manually by holding down the OPTION key. It appears the partitions are setup correctly although I would have chosen not to create a Linux Swap partition as it's really not needed unless you're short on memory.

    "GRUB" is the Linux boot loader and it should be where it's currently located. That looks OK as far as I can tell. I've never attempted to install the 64 bit version of Ubuntu (only 32 bit many times) so I can't be sure if everything is setup correctly.

    Follow the rEFIt instructions to remove it or just go to:

    MacIntosh HD/EFI and change the name of the folder to something like
    MacIntosh HD/EFI_save

    That will kill rEFIt and stop it from attempting to load GRUB. However, you will need to use the OPTION key to attempt to boot into Ubuntu after doing that.

  3. #3
    Quote Originally Posted by chscag View Post
    Remove rEFIt and try booting manually by holding down the OPTION key. It appears the partitions are setup correctly although I would have chosen not to create a Linux Swap partition as it's really not needed unless you're short on memory.

    "GRUB" is the Linux boot loader and it should be where it's currently located. That looks OK as far as I can tell. I've never attempted to install the 64 bit version of Ubuntu (only 32 bit many times) so I can't be sure if everything is setup correctly.

    Follow the rEFIt instructions to remove it or just go to:

    MacIntosh HD/EFI and change the name of the folder to something like
    MacIntosh HD/EFI_save

    That will kill rEFIt and stop it from attempting to load GRUB. However, you will need to use the OPTION key to attempt to boot into Ubuntu after doing that.
    Actually I did try without rEFIt. Still the same result except that I don't get to see the Tux logo - going straight into the black screen.

    I also installed Ubuntu 10.04LTS with the exact same results.

    What is that 'MBR contents: Boot Code: GRUB' telling me ?
    Does it see GRUB installed on a different (the main) partition too ?

    I think something is wrong with the main partition. No matter how I repartition the disk (swap before Linux, swap after Linux, different sizes) and what version of Ubuntu I install I end up with the same results.

  4. #4
    Unable to dual-boot Mac OSX an Ubuntu
    chscag's Avatar
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    Rep Power
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    What is that 'MBR contents: Boot Code: GRUB' telling me ?
    Does it see GRUB installed on a different (the main) partition too ?

    I think something is wrong with the main partition. No matter how I repartition the disk (swap before Linux, swap after Linux, different sizes) and what version of Ubuntu I install I end up with the same results.
    I missed that part about the main partition and MBR contents. But I need to ask something first before I can answer your question.

    Are you able to boot to OS X either by using the OPTION key or from rEFIt when it was installed?

    The reason for the question is... it appears that GRUB may have installed itself in the OS X boot sector. I've had that happen to me several times. Seems that sometimes the Ubuntu installer has a mind of its own.

    Let me know and we'll go from there.

  5. #5
    Quote Originally Posted by chscag View Post
    I missed that part about the main partition and MBR contents. But I need to ask something first before I can answer your question.

    Are you able to boot to OS X either by using the OPTION key or from rEFIt when it was installed?

    The reason for the question is... it appears that GRUB may have installed itself in the OS X boot sector. I've had that happen to me several times. Seems that sometimes the Ubuntu installer has a mind of its own.

    Let me know and we'll go from there.
    Yes, I am able to boot OS X with both methods.
    That's what I suspect too, that GRUB has been installed in the main partition as well - no idea how/when - and it overrides the one installed in the Linux partition.

  6. #6
    Unable to dual-boot Mac OSX an Ubuntu
    chscag's Avatar
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    Yeah, it's definitely telling you that GRUB is installed in the MBR (Master Boot Record).

    What's strange is that the partition table looks like it's OK and the partition order is likewise good. However, partition 3 is pointing to the GRUB boot code and it looks like that code is actually residing in the MBR.

    Which is why when you try to boot Ubuntu, a black screen and blinking cursor occurs because it can't find the GRUB boot loader.

    I think I would try completely removing Ubuntu and do another install to see what happens. I've had problems in the past with GRUB and the installer having a mind of its own, but I was always able to resolve it with another install. (That was dual booting with Window XP which is easier to setup than dual booting with OS X.)

    Before you remove Ubuntu and reinstall, reset your PRAM-NVRAM to make sure there's nothing residing there that's causing trouble. See this Apple LINK to reset.

  7. #7
    Quote Originally Posted by chscag View Post
    Yeah, it's definitely telling you that GRUB is installed in the MBR (Master Boot Record).

    What's strange is that the partition table looks like it's OK and the partition order is likewise good. However, partition 3 is pointing to the GRUB boot code and it looks like that code is actually residing in the MBR.

    Which is why when you try to boot Ubuntu, a black screen and blinking cursor occurs because it can't find the GRUB boot loader.

    I think I would try completely removing Ubuntu and do another install to see what happens. I've had problems in the past with GRUB and the installer having a mind of its own, but I was always able to resolve it with another install. (That was dual booting with Window XP which is easier to setup than dual booting with OS X.)

    Before you remove Ubuntu and reinstall, reset your PRAM-NVRAM to make sure there's nothing residing there that's causing trouble. See this Apple LINK to reset.
    I went on the assumption that the MBR is the only thing that is corrupt.

    So, I boot a Windows XP CD go into the 'Recovery Console' and run 'fixmbr' from the prompt, restarted and everything falls into place nicely.
    I can now boot with both rEFIt and the 'option' key.

    Thanks a lot for the feedback. It helped me narrow down the problem with some level of confidence.

  8. #8
    Unable to dual-boot Mac OSX an Ubuntu
    chscag's Avatar
    Member Since
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    Glad to hear it's working OK. Have fun with Ubuntu - it's a great OS. And visit us often.

  9. #9
    I'm having the same blinking cursor problem as the OP and don't want to open a repetitive thread. Can anyone help? I assume it's an issue that there's nothing listed for 2512896 - 97916927 under MBR partition table... but I'm a complete dual boot/Linux novice, so I don't want to try anything without input.

    *** Report for internal hard disk ***

    Current GPT partition table:
    # Start LBA End LBA Type
    1 40 409639 EFI System (FAT)
    2 97918400 976510983 Mac OS X HFS+
    3 411648 2512895 Linux Swap
    4 2512896 97916927 Basic Data

    Current MBR partition table:
    # A Start LBA End LBA Type
    1 1 39 ee EFI Protective
    2 40 409639 0b FAT32 (CHS)
    3 * 97918400 976510983 af Mac OS X HFS+
    4 411648 2512895 82 Linux swap / Solaris

    MBR contents:
    Boot Code: None

    Partition at LBA 40:
    Boot Code: None (Non-system disk message)
    File System: FAT32
    Listed in GPT as partition 1, type EFI System (FAT)
    Listed in MBR as partition 2, type 0b FAT32 (CHS)

    Partition at LBA 97918400:
    Boot Code: None
    File System: HFS Extended (HFS+)
    Listed in GPT as partition 2, type Mac OS X HFS+
    Listed in MBR as partition 3, type af Mac OS X HFS+, active

    Partition at LBA 411648:
    Boot Code: None
    File System: Unknown
    Listed in GPT as partition 3, type Linux Swap
    Listed in MBR as partition 4, type 82 Linux swap / Solaris

    Partition at LBA 2512896:
    Boot Code: GRUB
    File System: ext4
    Listed in GPT as partition 4, type Basic Data
    The walk-through I used for the install referred to possible partition issues, but reFIT didn't give me the option to sync partition tables; it returned an error and said it would not touch disk.

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