If you still can't boot from the USB flash drive, verify that you created the Mac OS installer on the USB flash drive while working in the same (or as close to) current Mac OS as you intend to write to the USB flash drive. If you can't see it, reset the PRAM and try again. On the machine you wish to install on, you can hold down the Option (ALT) key to select the boot drive, select your installer. Eject the drive if you're ready to remove the USB Drive and install.Deselect the check box ignore ownership.Click the padlock icon to unlock administrator options.In the info window, expand the Sharing & Permissions: section.Mounting the USB flash drive on the desktop, right click and select 'Get Info'.The 'missing step', after ensuring the USB flash drive is formatted correctly, is to ignore ownership For this reason, you will need to enable it before/after completing the process described by Apple, MacWorld and others using the 'createinstallmedia' command in the Terminal window. Complicating matters, the USB flash drive default may disable boot support.

Most of the guides, including Apple's own support doc on how to create a bootable Mac OS installer on USB - as of this date - fail to mention the ownership step.įirst and foremost, the USB flash drive must support ownership functionality. It may be that boot-up from the USB flash drive is 'prohibited' because your USB flash drive requires adjustment to the 'ownership' settings.

Install os x from usb