[RFC] initoverlayfs - a scalable initial filesystem

[Stephen Smoogen]

On Tue, 12 Dec 2023 at 12:38, Lennart Poettering <lennart at poettering.net>
wrote:

> On Mo, 11.12.23 12:48, Eric Curtin (ecurtin at redhat.com) wrote:
>
> > Sort of yes, but preferably using that __initramfs_start /
> > initrd_start buffer as is without copying any bytes anywhere else and
> > without teaching the bootloaders to do things.
> >
> > The "memmap=" approach you suggested sounds like what we are thinking,
> > but do you think we could do this without teaching bootloaders to do
> > new things?
>
> Well, in a standard UEFI world it would suffice to teach the memmap=
> logic to the stub that is glued in front of the kernel. For example,
> make sd-stub find the erofs initrd in the UKI, then trivially
> synthesize a memmap= switch and append it to the kernel command line.
>
> but of course, you don't believe in UEFI or good boot loaders, so you
> kinda dug your own grave here...
>
>
To clarify here.. it is not that we don't believe in UEFI or good boot
loaders, it is more that the various hardware being tasked to these
scenarios does not come with it. This is more of trying to make the best
with the ingredients we have, and realizing what we end up with will not be
as palatable as we wished. We all know that having UEFI or coreboot would
make this so much easier and better, but it would have taken the board
designers to have realized that nearly a decade ago since that is when
initial board designs seem to have been chosen. Even if they realized it at
this moment.. we would still be dealing with this for a while.

At this point it isn't that we are trying to dig this grave any deeper, but
are trying to come up with ways to dig out of it :). Some of the proposed
solutions may not do that, but it is what is being tried.



> (The main reason why sd-stub doesn't actually support erofs-initrds,
> is that sd-stub also generates initrd cpios on the fly, to pass
> credentials and system extension images to the kernel, and you can't
> really mix erofs and cpio initrds into one)
>
> Lennart
>
> --
> Lennart Poettering, Berlin
>
>

-- 
Stephen Smoogen, Red Hat Automotive
Let us be kind to one another, for most of us are fighting a hard battle.
-- Ian MacClaren
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