[coreboot] Rettungsboot

[Nico Huber]

On 26.11.2016 19:18, Igor Skochinsky wrote:
> Hello Nico,
> 
> Saturday, November 26, 2016, 6:42:40 PM, you wrote:
> 
> NH> Hey coreboot folks,
> NH> here's something that's bugging me for a long time: Our lack of an out-
> NH> of-the-box booting experience.
> 
> NH> All our payloads that don't implement legacy boot facilities (i.e. BIOS,
> NH> UEFI), only work in the usual case, to boot an installed OS that's con-
> NH> figured to work with that payload. But they stink at booting in the un-
> NH> usual case, e.g. from installation, rescue or live boot media.
> 
> NH> One could now point a finger at the developers of those media and say,
> NH> they only have an MBR / UEFI boot partition, no GRUB / FILO / whatever
> NH> configuration file. So it's their fault? Well, I say, it's our fault!
> NH> We never specified how a civilized, general booting process shall look
> NH> like.
> 
> NH> My proposal: Let's specify a fallback boot mechanism for bootloaders for
> NH> the case they feel lost. This would include
> 
> NH>   o a configuration file format (to specify a binary to load along
> NH>     with its parameters),
> 
> NH>   o a search scheme for the configuration file (e.g. search the first
> NH>     partition of each disk for `/boot/rettungsboot`),
> 
> NH>   o a set of supported partition table formats,
> 
> NH>   o a set of supported file systems,
> 
> NH>   o a set of binary formats that one can expect the payload to support
> NH>     (e.g. multiboot2, multiboot, bzImage).
> 
> NH> The configuration file format should be most lean and simple. We might
> NH> want support for multiple options (i.e. a simple menu) though. Some-
> NH> thing like the legacy GRUB format maybe?
> NH> What do you think?
> 
> https://xkcd.com/927/ comes to mind immediately.

Of course, it does ;)

> 
> What would be the incentive for the boot media creators to support yet
> another booting format, supported by a tiny amount of systems?

I have to admit that my view on boot media is very limited. I have al-
most exclusively free software developers in mind and I hope they would
be responsive to a non-proprietary alternative or at least accept pat-
ches.

> Why not instead consider including a minimal subset of SeaBIOS or
> Tianocore (enough for booting),

This could bloat a bootloader by a huge factor just for compatibility.
It would be hard to implement, even harder to maintain.

It's also about the impression someone gets after installing coreboot.
Legacy boot just doesn't fit in there: We have this nice, fast boot
but to actually use it you have to load a ton of extra software between
coreboot and your OS?

> or maybe do a survey and try to support the most common
> variations of grub/isolinux etc used on such CDs?

I had that in mind too, for some time. It would be less bloating than
legacy boot support but still leave a lot to implement and maintain. As
you mentioned GRUB, have you looked at it's file format lately? It's
more a shell scripting language than configuration.

Being a workaround hidden from the media creators, it's also unlikely
that it wouldn't break right in the moment you need it most.

To sum it up, I want something that is lean and clean enough so it could
be added to any bootloader. Even if that boot loader is not of the
let's build a tiny OS type. When I boot a machine the first time with
coreboot I want it to come up and be able to install an OS, without any
workaround.

Nico