Plugin efibootguard-boot doesn't support to specify root parameter with unified kernel image

Plugin efibootguard-boot doesn't support to specify root parameter with unified kernel image

[Mou, ChengShu(Ben)]

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Hi all,

I have a target image with following partitions:

|- bootloader (efibootguard)
|- system A (linux.efi)
|- system B (linux.efi)
|- root FS A
|- root FS B

My plan is to use plugin efibootguard-boot to generate linux.efi respectively for system A/B and they can mount related root FS. So, I need to specify root parameter respectively in linux.efi.
After checking the code, I found that there is only 1 place to specify it, bootloader command with option --append in wks file. This method can only specify 1 root parameter.

I have tried to modify this plugin as following:
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Within this modification, linux.efi could contain its own root parameter.

I don't know if it is a right way, please let me know if you have some suggestions. Thanks in advance.

With best regards,
Cheng Shu Mou

Siemens Ltd., China
RC-CN DI FA BL IE
Tianyuan road No.99
611731 CHENGDU, China
mailto:chengshu.mou@siemens.com
www.siemens.com<https://siemens.com>
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Re: [cip-dev] Plugin efibootguard-boot doesn't support to specify root parameter with unified kernel image

[Gylstorff Quirin]

Hi  Cheng Shu Mou,

On 10/8/22 11:10, Mou, ChengShu(Ben) via lists.cip-project.org wrote:
> Hi all,
> 
> I have a target image with following partitions:
> 
> |- bootloader (efibootguard)
> 
> |- system A (linux.efi)
> 
> |- system B (linux.efi)
> 
> |- root FS A
> 
> |- root FS B
> 
> My plan is to use plugin efibootguard-boot to generate linux.efi 
> respectively for system A/B and they can mount related root FS. So, I 
> need to specify root parameter respectively in linux.efi.
> 
> After checking the code, I found that there is only 1 place to specify 
> it, bootloader command with option --append in wks file. This method can 
> only specify 1 root parameter.
> 
> I have tried to modify this plugin as following:

Could please you sent your modification the next time as patch or text 
snippet?


> 
> Within this modification, linux.efi could contain its own root parameter.
> 

> I don’t know if it is a right way, please let me know if you have some 
> suggestions. Thanks in advance.
With a fixed root parameter you need to ensure
that the partition you update is on all devices the same, e.g.
A	->	B	->	A
1.0 	-> 	1.1	->	1.2

For example this does not work:
A	->	A
1.0	->	1.2

The customer needs to update first to 1.1 and B before updating to 1.2.

In cip we have solved this issue of root fs selection by adding a uuid 
or use verity checksum to identify the root file system corresponding to 
the linux.efi. This allows us to update independent from the root 
parameter.

Kind regards,

Quirin