Why won't my MacBook Air boot from an EFI USB stick?

Tech Talk MacOS
1

I fancy playing with ChromeOS Flex on an old MBA i7 (MBA 6,1). It’s listed as a tested/supported device by Google.

Created the ChromeOS recovery USB. Put it into the MBA, booted with ALT key pressed, selected ‘EFI Boot’ to boot from - and all I get is a black screen.

Any ideas? I’ve checked the USB, it’s readable, has EFI/BOOT directories and files on it.

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2

Did you go into recovery mode first and enable booting from external media?

Allowing an Intel Mac to Use External Boot Media

For an Intel Mac, do the following:

  • Reboot the Mac, then immediately hold Command + R keys to load into Recovery Mode
  • Pull down the Utilities menu, then choose “Startup Security Utility”
  • Under the External Boot section, check the box for “Allow booting from external media” to prevent boot restrictions
  • Reboot the Mac again, holding OPTION to boot from a boot disk should work now

Only Macs with a T2 chip need to do this. The T2 chip is typically included with an Intel Mac that has a Touch Bar or Touch ID.

Using the OPTION key to load the boot menu and choose an external disk should work fine after this.

(Advice from OS X Daily:)

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3

Thanks. I’ll have a read. Mine doesn’t have the T2. I looked in recovery options, the only setting I could find was adding a password to boot from another disk, which isn’t set.

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