Bootable Disk

Discussion in 'Mac Pro' started by Apple Architect, Dec 8, 2010.

  1. Apple Architect macrumors regular

    Apr 4, 2007
    Have a challenge.

    I have recently added an SSD drive to my system and cloned the original main drive. As I make use of bootcamp deleted the bootcamp partition from the original drive and plan to use it just as a data disk (it already has my data on it).

    Disk A:
    Mac OS​
    Windows 7 (in bootcamp)​
    Disk B:
    Mac Data disk​

    The trouble is I am now being presented with 3 disk options on start-up as both the SSD and the original disk OS X instances are showing (as well as the Windows).

    How do I stop the original disk being bootable ?

    I have taken a look at fdisk and diskutil which both show that the original disk has the bootable flag set - but I have no idea how to remove the setting.

    Any help greatly appreciated.
  2. gr8tfly macrumors 603


    Oct 29, 2006
    ~119W 34N
    System Preferencs > Startup disk

    Select the volume you want to boot from. It will then be used as your default boot volume.

    Unless you always hold down the option key on startup, you shouldn't be seeing a list of boot options.

    If you need to go a step further, and render the volume unable to boot, there are a set of files you can remove, some hidden. Can't think of the whole list, at the moment, though. Is one of your goals to remove the OS entirely from that volume?
  3. Dalton63841 macrumors 65816


    Nov 27, 2010
    If you formatted the data disk to remove the operating system from it, it should not show up as bootable.
  4. Apple Architect thread starter macrumors regular

    Apr 4, 2007
    Yes that is the plan. I really don't want to have to reform the drive as it will just mean copying LOTS of data off, then back on.....

    Given i spend a lot of time switching between Mac and Windows I thought I would simply tidy up the boot screen.....the extra disk does not need to be there.
  5. philipma1957 macrumors 603


    Apr 13, 2010
    Howell, New Jersey
    MY question is will the extra boot disk really boot? Sounds like it will. If so you have an instant backup in case the new boot disk crashes. You also have a backup boot disk in case you install some update that hurts your current boot disk. Osx 10.6.6 for example may knock out your printer you would have the older boot disk for a quick fix.
  6. cutterman macrumors regular

    Apr 27, 2010
    This article may address the OP's question. If the folders (esp /System) and mach_kernel file listed in that reference are deleted the volume will not likely show up as bootable.

    I agree with the previous post though. It is a good idea to have a backup booting OS X partition, as this will greatly simplify troubleshooting and disaster recovery. You can also use it to test new updates and software installs.
  7. Apple Architect thread starter macrumors regular

    Apr 4, 2007
    Thnaks for this. Hopefully this is exactly what I need. Although I understand the "good to ahve a second OS disk" I already have this on external media.

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