Help! Failure to recognize internal HD after installing Ubuntu 9.10 on external drive

[BUKiT]

Here's my system: running Mac OSX 10.6.4 on black Macbook 2.4 GHz w/ 4 GB 667 MHz DDR2 SDRAM

I recently downloaded Ubuntu 9.10 64-bit and attempted to install it to an existing 35 GB partition on an external hard drive using my Macbook. I did this by shutting down my computer, plugging in the external drive, and booting from a CD to which I had burned the .iso file using Disk Utility. I selected my desired language and chose to install Ubuntu. After manually selecting the desired partition, I resized it to 25 GB, formatted it to ext4, and mounted it as "/". I then used the remaining free space to form an additional partition of 8 GB (double my RAM) for use as "swap space" as recommended by the installer. The rest of the installation steps were uneventful, and I restarted my computer at the end of the installation.

I also have a second copy of Mac OSX 10.6.4 installed on one of the external HDD's other partitions, and the computer booted straight into that partition when restarted. After shutting the system down again and booting using the "option" key, the computer only gave me the option of booting into the Mac OSX partition on my external drive - the Ubuntu partition and my internal hard drive were conspicuously absent.

I have since tried shutting down the computer and booting without the external HDD plugged in, and all I get is a grey screen with a flashing folder/question mark icon. With the external drive plugged in, I can still boot from the external Mac OSX partition and access the contents of my internal hard drive, which appear completely intact.

In the short term, I need to rid myself of the grey screen with flashing folder/question mark and boot directly into my internal hard drive without the external HDD attached. My long term goal is to be able to plug in the external drive, boot holding down the "option" key, and have my choice of booting into Ubuntu 9.10 x64, OSX (internal), or OSX (external). Is this wishful thinking?

Any advice is greatly appreciated. Thanks.

 

[cradom]

To try and fix one problem, booting from the internal drive -
try booting from the install disk, running Startup Disk from the menu and see if you can select the internal drive.

Edit: or for that matter, running Startup Disk from System Preferences on the bootable partition.

 

[BUKiT]

I attempted to use the Startup Disk panel in System Preferences on the external OSX partition to specify the internal hard drive, but that didn't seem to make a difference. I also tried repairing the disk permissions using Disk Utility, but that didn't do anything either.

I'm thinking the Master Boot Record on my internal hard drive may have been overwritten by the Linux GRUB bootloader. Does anyone know how to go about repairing this?

 

[cradom]

Grub is a little beyond me. Have you tried posting on the Ubuntu forums?
Ubuntu Forums

 

[chscag]

First off, I don't know where you got 10.6.4 from because Apple just issued the 10.6.3 update like two days ago.

I'm thinking the Master Boot Record on my internal hard drive may have been overwritten by the Linux GRUB bootloader. Does anyone know how to go about repairing this?

As far as your problem is concerned.... You've probably overwritten your OS X boot sector with GRUB as you indicate above. It seems to be a common mishap when trying to install Ubuntu. The Ubuntu installer is not for the feint of heart in the first place, even when installing a dual boot Windows system where it's easier to control.

As far as repairing it, you can give this method a try (it has worked for others. This was copied from the OS X Hints forum)

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Restore default bootloader without harming partitions

Fri, Nov 20 2009 at 7:30AM PST • Contributed by: tofergregg

If your bootloader gets changed or corrupted, this fix will restore it without damage to your disk partitions.

This hint may be a bit esoteric, but I thought I was up for a long night of reinstallation pain before stumbling upon this fix. I made the mistake of trying to use an Ubuntu 9.04 boot CD to install Ubuntu to an external (USB) drive on my Mac.

Don't do this, unless you know the following: Regardless of the fact that you chose the external drive upon which to install Ubuntu, you won't be able to boot back into your Mac without changing the bootloader. I ended up with the dreaded question mark folder when I tried to reboot my Mac, and nothing worked to boot into my OS X partition.

Luckily, I have a bootable external drive with OS X on it, and I was able to boot into it by holding down the Option key (the primary partition still did not show up).

I started searching online for the fix, and it seems that Ubuntu changes the Darwin (default) bootloader to Grub on your internal disk, and OS X won't use it (at least not by default). The fixes listed were kludgy, and amounted to either installing another third party bootloader (called "rEFIt") or completely wiping your internal drive and reinstalling OS X (even a standard install won't work).

Anyway, the fix turned out to be easy with Disk Utility (and probably possible from the OS X boot disc). Run Disk Utility and click on your internal hard disk (the disk itself, not the partition under it). Then click on the Partition tab. If you move the triangular slider that adjusts the partition up and then back to where it was, the "Apply" button becomes active (it starts greyed out). You can now click "Apply," and the partition will be left alone, but the bootloader will be recreated.

When I did this, a window popped up that said, "Are you sure you want to partition the disk? Partitioning this disk will change some of the partitions. No partitions will be erased." If you get a message that partitions will be erased, I'd look into it more before going ahead!

I was surprised that this worked, but when I rebooted, the computer booted straight into OS X from the internal drive.

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Let us know if this works for you. By the way, the next time you decide to install Ubuntu, use "rEFIt". I'll let you do the research on that.

Regards.