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Concerning a MacBook Pro with Snow Leopard. As you know when pressing alt during startup there is the possibility of selecting which disc/drive/memory you want to boot from. For example if you have a CD/DVD inserted in the computer or Bootcamp Windows installed they can be selectable to boot from.

Here's what I want to do: I want that when I have a USB stick inserted to the computer, I want to be able to boot from that in the same manner as can be done with e.g. a DVD.

The problem is that when I have a USB stick connected to the computer during startup and press alt, the USB is not selectable to boot from. So the question is: How can I enable the computer to (during startup) select a connected USB stick to boot from?

I have tried a program called rEFit, which gives you another menu during startup, where you can for example select if you want to boot from any partition that you created. Unfortunately it still doesn't enable booting from a connected USB stick, at least not automatically. So I wonder how to enable booting from a USB stick, either in this program, or otherwise.

If you have done this yourself, or if you have any good ideas on how to enable it, please share.

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2 Answers 2

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USB thumb drives behave much like internal hard drives in terms of booting from it on a Mac. Therefore, it depends on what you have on those drives. If there is "just data" on the USB stick, it will, very much like "data" hard drives, not show up at the boot picker.

As a test, you can try to install a for your system supported version of Mac OS X onto the USB stick and then see whether it shows or not (I would understand that it will show thereafter as all Intel Macs can boot from USB).

NOTE: For obvious reasons, you should back up whatever you have on the USB stick before attempting this.

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  • So how can you enable booting from a USB stick even if it contains "just data"? Like with rEFit you can choose to boot from any partition, even if a partition doesn't contains anything.
    – App
    Commented Apr 5, 2015 at 8:55
  • You don't - the drive must be bootable. You couldn't, for instance, boot from a drive that only contained video files; it must be a truly bootable system drive
    – Tetsujin
    Commented Apr 5, 2015 at 10:05
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You can only boot from a USB device if it contains the necessary startup files required for your Mac, generally either an operating system or operating system installation files. You could install OS X on a USB stick or drive, or you could use Disk Utility's Restore function to copy a bootable DVD/CD (or disk image) to a USB stick.

Without the necessary startup files there is nothing to boot the system - only bootable devices will appear in the Mac boot picker.

REFInd/rEFIt is simply a boot selector/manager that hooks into the OS X startup sequence, giving more flexible options for alternative boot sources. It isn't any sort of boot enabler and doesn't make devices bootable in the absence of an operating system or startup files.

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  • Maybe I should elaborate on what I want to do. I want to use the USB stick as a boot disc for Windows bootcamp - or more specifically as a startup disc for a Windows Bootcamp that has been encrypted. There is an encryption program in Windows called BitLocker, but in order to use that one has to boot the computer from a USB stick. Preparing the USB stick for this in BitLocker is no problem, but when it comes to rebooting the computer, and needing to boot from the USB stick, it is not possible to select to boot from it. That's what I want to do. So how is it possible to enable this?
    – App
    Commented Apr 5, 2015 at 10:10
  • BitLocker simply requires a USB stick for storing its encryption keys rather than entering a password each time you start Windows. It's not actually used to boot Windows hence it won't appear in the boot picker, it only needs to be present so Windows can access the encryption keys to authenticate and decrypt those drives you've encrypted. When using BitLocker Windows will boot from the System Reserved partition. Are you struggling to boot your Mac after turning BitLocker on, even though you have inserted a suitable USB drive with the encryption keys?
    – ScunnerDarkly
    Commented Apr 5, 2015 at 14:29
  • Yes When using BitLocker I select "Run BitLocker system check (The system check will ensure that BitLocker can read the recovery and encryption keys before encrypting the drive)". But after restarting there comes up this error message: "BitLocker could not be enabled. The BitLocker startup key or recovery password cannot be found on the USB device. Verify that you have the correct USB device, that the USB device is plugged into the computer on an active USB port, restart the computer, and then try again. If the problem persists, contact the computer manufacturer for BIOS upgrade instructions."
    – App
    Commented Apr 5, 2015 at 15:00
  • Take a look at this article, it may provide the answer you seek... blogs.technet.com/b/askcore/archive/2011/06/10/…
    – ScunnerDarkly
    Commented Apr 5, 2015 at 15:27
  • Thanks for the link, I tried following all the steps there exactly but unfortunately it still didn't work. I still get the same error message as the one I wrote before: "BitLocker could not be enabled. The BitLocker startup key or recovery password cannot be found on the USB device. Verify that you have the correct USB device, that the USB device is plugged into the computer on an active USB port, restart the computer, and then try again. If the problem persists, contact the computer manufacturer for BIOS upgrade instructions."
    – App
    Commented Apr 5, 2015 at 20:56

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