Chromebook - Alternate firmware editing boot options

Support
1

Hardware = Acer Chromebook 314

Firmware = Google__Craask.15217.319.0 09/10/23

I have successfully installed RW_LEGACY using firmware-util script.

I am trying to add a boot option in this alternate firmware.

I have located the grub file that works and boots Ubuntu Cinnamon 22.04


<x86_64-efi>
grub.efi

This works when using “Boot From File” in Boot Manager.

However, when i try and add this as a boot option i can select the same grub.efi file but cannot add a description/title, So when i save the edit the option does not appear under Boot Options.

Does this mean we cant make changes using the RW_LEGACY firmware?

2

RW_LEGACY doesn’t have NVRAM support so you can’t make or save any boot entries.

3

I thought it might be something along those lines, thanks for clarifying. :+1:

4

Rw_leagcy mean read write leagcy but it can access right protected parts of chrome os

5

I have disabled firmware write protection
So i guess i can edit any part of it
Is there any hope for me regarding the same issue…?

6

No, because you don’t seem to understand the issue. Stock firmware + edk2 doesn’t have NVRAM support.

7

Sorry, I am quite a rookie in this stuff :sweat_smile:
But yet there was another thing up in my mind
I Can still see Some of the default boot options which always remain there (verified image A,B…)
I was wondering if i could get to know the location of boot files they are referring to and if i could create symlink(or just copy paste ) of my own boot files
Could that be possible (Again "Sorry if this sounds stupid, I am a newbie :smile:)

8

That’s just GRUB. You can freely edit grub entries. “Verified image A/B” comes from ChromeOS’ EFI partition. I’m not sure why you didn’t replace it when you installed a Linux distro, since it doesn’t really do anything.

9

I still have my linux installed
Can you assist me replacing it with grub of my choice
EDIT: I just mounted the efi drive and copy pasted my /boot/efi/ to it and it was done

10

Hi, is the lack of NVRAM support for RW_LEGACY also why I lose the EDK2 firmware after going through Chromebook Recovery process. Is there a way to prevent this (other than stop using Recovery :smile:)

I’m trying to learn all about firmware process etc. but so far not sure U-Boot will be able to boot USB so totally reliant on EDK2 .

Thanks

11

Recovery overwrites the RW sections of the firmware to stock, including reverting the RW_LEGACY portion to whatever Google’s implementation is for your board. Most of the time the stock RW_LEGACY doesn’t do anything/is missing basic functionality (whether it’s U-Boot or Tianocore or whatever), which is why you have to flash MrChromebox’s EDKII payload in the first place.