Mac OS X: Booting Intel-Mac From External HDD

“You cannot install Mac OS X on this volume…” alert in Installer

If you’re trying to install Mac OS X on a hard disk that you’ve connected to your Intel-based Mac, you may see this alert in Installer and be unable to select the disk for installation:

“You cannot install Mac OS X on this volume. Mac OS X cannot start up from this volume.”

Select a Destination

The Mac OS X installer prevents you from installing on to a disk that uses a non-native partition scheme (or to any volumes on that disk). PowerPC-based Macs and Intel-based Macs have different native partition schemes (see additional information below).

Solution

To install Mac OS X on the disk, you must partition the drive to match the native partition scheme for your computer’s processor type (Intel or PowerPC). Partitioning splits the disk into two or more volumes (though you can choose just one partition to resolve this particular issue, as described below).

Important: Partitioning erases the contents of the drive. Additionally, simply erasing the drive without partitioning will not resolve the issue (see Additional information, below).

Follow these steps:

  1. Back up your important data. Partitioning a hard disk erases all data on the disk.
  2. Open Disk Utility:
    • If you’re started from a Mac OS X installation disc, choose Disk Utility from the Utilities menu.
    • If you’re started from your computer’s Mac OS X volume, open Disk Utility from the Utilities folder. You can get there by choosing Utilities from the Finder’s Go menu.
  3. Select the disk you want to partition (that is, the disk you want to install Mac OS X on. The disk contains size and model number of the drive, not “Macintosh HD” or a name you chose.
  4. Click the Partition tab in the Disk Utility window. If the partition tab is not visible, make sure you’ve selected the disk (not volume) in the left side of the window.
    Tip: In Disk Utility, volume names are indented on the left side of the window. Disk names are not indented.
  5. Choose the desired number of partitions from the Volume Scheme pop-up menu. It’s OK to choose “1 Partition” if you only want one.
  6. Click Options.
    Note: On some Intel-based Macs, the Options button does not appear under the partition tab. Use the erase tab to erase the disk instead. This will change the partition scheme to the default “GUID Partition Scheme”. You can then use the partition tab to create additional partitions if desired.
  7. From the Partition Scheme pop-up menu, choose “GUID Partition Scheme”.
  8. Click OK.
  9. Make any other changes you wish in the Volume Information section, such as partition size(s) or naming.
  10. Click the Partition button to erase your disk and install the new partition scheme.
  11. When partitioning finishes, you should be able to install Mac OS X on the volume. Afterwards, you can restore backed-up data.

Additional Information

Installer refers to the volume, but the issue is actually with the entire hard disk (specifically, with its partition scheme). That’s why erasing the volume without re-partitioning the disk will not resolve the issue. Use Disk Utility as noted above to repartition the disk, using the GUID partition scheme.

Intel- and PowerPC-based Macs have different native partition schemes. The Mac OS X installer keeps you from selecting a hard disk that uses a different partition scheme (or any volumes on that disk) for installation. You can still use such disks for other storage purposes, swapping the disk back and forth between Intel- and PowerPC-based Macs if desired.

For more information on partition schemes, see this Apple Developer Connection website.

Discovering the partition scheme

You can easily find out what partition scheme a disk has using Disk Utility.

  1. Open Disk Utility:
    • If you’re started from a Mac OS X installation disc, choose Disk Utility from the Utilities menu.
    • If you’re started from your computer’s Mac OS X volume, open Disk Utility from the Utilities folder. You can get there by choosing Utilities from the Finder’s Go menu.
  2. Select the hard disk (not the volume) in the left side of the Disk Utility window. The disk usually contains the name of the drive vendor, not “Macintosh HD” or a name you chose.
    Tip: Select the hard disk (not the volume) in the left side of the Disk Utility window. The disk usually contains the name of the drive vendor, not “Macintosh HD” or a name you chose.
  3. From the Disk Utility File menu, choose Get Info.
  4. Look for the “Partition Type:” line.
    • A PowerPC-based Mac can only install Mac OS X on a disk with the “Apple_partition_scheme.”
    • An Intel-based Mac can only install Mac OS X on a disk with the “GUID_partition_scheme.”

Article reprinted from Apple.com.

6 thoughts on “Mac OS X: Booting Intel-Mac From External HDD”

  1. Pls help me.When i tryed to install macosx10.5 leopard on my Intel pc they can’t find my Hard disk.

  2. I need a little bit more info that that. When you say it can’t find your hard disk, your talking about your built in hard drive or an external USB/Firewire drive?

  3. I am telling about my built in hard drive.The Installation reches the license agriment and after hat it searching form my HDD but it can’t find my configuration is

    Intel(R) CPU 2.80Ghz
    2.80Ghz,896MB of RAM
    40 gb HDD

    Please help me to install MAC

  4. Sorry for delayed response. Do you have another Intel Mac around? Do a target disc mode (from shutdown or restart, press and hold T until FireWire logo appears) on the Mac that isn’t detecting your hard drive and plug it into another Intel Mac via firewire and see if it picks up the hard drive. If it does, your hard drive is OK andit might be the installation disk. Does the Mac boot up to Jaguar or it doesn’t even boot into any OS?

  5. No I am living in India, Kerala.And in my town there is no mac users wat to do Is thre any other way.Sorry 4 the disturbnce

  6. Do you have an external FireWire hard drive?

    Stick you Leopard DVD in and when it loads the installer, run Disk Utility and see if the hard drive is showing up. Run a Verify Disk and Repair Disk. Try also Fix File Permission.

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