8

On Mac OS X there is a tool called nvram to get and set EFI properties. As I am now deploying GNU/Linux on Apple hardware, I'd like to have a similar tool that is able to talk to Apple's EFI implementation.

Are there tools to achieve this?

Improve this question
7
  • 1
    you should just be able to read them with the efivars program available via package manager. However, if you took the (horrible!) advice offered by many - such as at this Ubuntu/Mac how-to - and converted your disk to a Hybrid MBR so you might boot Linux in legacy (read - BIOS) mode, then those variables are not available to you and will not be until you boot the Linux kernel in EFI-mode. Here is a far better tutorial on the subject.
    – mikeserv
    Sep 8, 2014 at 3:06
  • 1
    There's /sys/firmware/efi/vars/ holding those on my UEFI compatible systems upon efivars.ko module load but it was known a year or two ago that loading it might corrupt Apple's firmware, it was advised that one backs it up and has the backout plan/tools handy (see also rodsbooks.com/efi-bootloaders/installation.html).
    – Michael Shigorin
    Sep 8, 2014 at 13:08
  • @mikeserv efivars works, at least for reading. About all those Apple-Firmwares-Will-Be-Destroyed-Warnings... I never got authoritative information about that.
    – bot47
    Sep 8, 2014 at 22:01
  • @mikeserv Would you write an answer about efivars?
    – bot47
    Sep 8, 2014 at 22:02
  • I dont have any Apples and so i dont know the ins and outs well enough to make any authoritative calls in that respect. Youre far better off cruising rodsbooks as Michael has suggested - Rod Smith is about as authoritative as it gets in my opinion on this subject. I do know that theres little mystery there - i can read those with printf and od in a pinch. You might also look into the clover bootloader forums - which is the other active refit fork and is what all of the hackintosh guys use. I am curious though and i may dig into it. Can i ask - what do you wanna do with them?
    – mikeserv
    Sep 8, 2014 at 22:13

1 Answer 1

Reset to default
1

The tools available are going to vary between Linux distributions, but with a Ubuntu 16.04 LTS live ISO booted from a USB stick on a 2011 MacBook Pro, nvram variables are readable in the filesystem:

ubuntu@ubuntu:~$ cd /sys/firmware/efi/efivars/
ubuntu@ubuntu:/sys/firmware/efi/efivars$ ls
AAPL,PathProperties0000-4d1ede05-38c7-4a6a-9cc6-4bcca8b38c14
AcpiGlobalVariable-af9ffd67-ec10-488a-9dfc-6cbf5ee22c2e
[...]
ThorUpdateResult-7c436110-ab2a-4bbb-a880-fe41995c9f82
Timeout-8be4df61-93ca-11d2-aa0d-00e098032b8c
ubuntu@ubuntu:/sys/firmware/efi/efivars$ hexdump -C Lang-*
00000000  07 00 00 00 65 6e 67                              |....eng|
00000007

To modify variables, install the efivar tool with apt.

Improve this answer

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .