Sunday, February 26, 2012

Restoring the Apple's EFI on a MacBookPro with Linux

Recently, you installed GNU/Linux and deleted the /EFI/APPLE directory.
But now, you need to boot from a USB key and holding the Option button no longer works! Even the recoveryHD USB doesn't work.
Why? Because this code was located in /EFI/APPLE/.

Here is how to restore it and why not, keep your EFI up to date on a macbook pro without having MacOSX installed.

First, download the EFI update for your model:
In my case, I have a MacBookPro8,2 so I downloaded MBP81.0047.B27 (EFI 2.7).

The DMG which is uncompressed is supposed to be moutabled under Linux using either:
$sudo mount -t hfs -o loop myImage.dmg /mnt
$sudo mount -t hfsplus -o loop myImage.dmg /mnt

However, I was not able do it so I had to fallback to another MacOSX installation from which I retrieved the .pkg.
Feel free to share yur experiences with DMGs under Linux!

The .pkg file is actually a xar archive (
So, install xar and uncompress the .pkg using:
$xar -xf /mnt/MacBookProEFIUpdate.pkg

In the uncompressed directory, the Payload file is actually a .tar.gz archive so uncompress it:
$tar zxf Payload

Then go in the newly created System directory and follows subdirectories until you find a .scap file. It is named like MBP81_0047_27B_LOCKED.scap.
Assuming your EFI partition is located at /boot/efi, copy this file to /boot/efi/EFI/APPLE/FIRMWARE
Do not forget to create the /boot/efi/EFI/APPLE/EXTENSIONS directory.

You can reboot, it should work again!


  1. cool stuff
    if worse comes to it. USB SPI flash. backup chip first, then merge the data of the .scap with backup.bin in hexeditor.

    i been tinkering with this EFI and seen stuff of owner name, email and more in a gap-006... in a .rom
    i used xsearch in windows with phoenixmod tool dump folder to find username info.

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