Mac won't reboot with external drive connected

Discussion in 'macOS High Sierra (10.13)' started by Jigga Beef, Apr 1, 2018.

  1. Jigga Beef macrumors regular

    Jan 11, 2009
    Philadelphia, Pa
    Mac won't reboot with the external drive connected

    I have Mac Pro running High Sierra
    When i have a USB drive plugged in with a cloned boot drive (which i cloned with CCC) my mac won't boot up.

    The Start-Up disk is selected properly

    Assuming there's a setting I'm missing but can't figure it out.
  2. Jigga Beef thread starter macrumors regular

    Jan 11, 2009
    Philadelphia, Pa
  3. Fishrrman macrumors P6


    Feb 20, 2009
    Are you saying it won't "boot from the clone"?
    Or are you saying it won't boot AT ALL?

    Have you tried booting with the option key held down (until the startup manager appears)?
    Then, select the external drive with the pointer and hit return.

    If it won't boot from the clone, I'd try this:
    1. Use Disk Utility to ERASE the cloned backup. NUKE IT BACK TO ZERO -- Mac OS extended with journaling enabled.
    2. Use CCC to repeat the cloned backup -- all over again (yes, I realize this will take some time).
    3. Try to boot from it again.

    Additional questions:
    Who made the external drive?
    How old is it?
    Are you connecting "through a USB hub", or is the drive plugged directly into the Mac?

    There are -some- USB external drives that may not be capable of booting the Mac. This is usually due to the drive controller board -- doesn't have anything to do with the OS on the drive.

    There are some older Macs that won't boot from USB at all.
  4. Jigga Beef thread starter macrumors regular

    Jan 11, 2009
    Philadelphia, Pa

    Sorry, I should have been more clear. It won't boot at all with the drive plugged in. I don't want it to be boot from the clone drive but the internal drive that works when the USB drive isn't plugged in. Its a WD My Passport.
  5. DeltaMac macrumors G3


    Jul 30, 2003
    So - only that WD external drive, and any other drive (or other USB devices) attached doesn't affect booting at all?

    What happens if you simply let the Mac try to boot with the WD drive attached? Give it 10 minutes, minimum.
    Do you ever see the normal Apple icon, or see a blinking folder, or the "prohibited" symbol (circle crossed with diagonal line) - or anything at all appears on the display? Or nothing whatsoever, and the LED on the front of your Mac Pro flashes in

    Finally, is the WD plugged directly in to a rear USB port, or is it plugged in to an external USB hub?

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