[RFC] initoverlayfs - a scalable initial filesystem

[Lennart Poettering]

On Do, 14.12.23 02:17, Nils Kattenbeck (nilskemail at gmail.com) wrote:

> On Wed, Dec 13, 2023 at 10:03 AM Lennart Poettering
> <lennart at poettering.net> wrote:
> >
> > On Di, 12.12.23 23:01, Nils Kattenbeck (nilskemail at gmail.com) wrote:
> >
> > > > sysexts are erofs or squashfs file systems with verity backing. Only
> > > > the sectors you access are decompressed.
> > >
> > > Okay I forgot that they were erofs based and mentioned cpio archives
> > > so I assumed they would be one.
> > > Do they need to be fully read from disk to generate the cpio archive?
> >
> > erofs is a file system, cpio is a serialized archive. Two different
> > things. The discussion here is whether to pass the initrd to the
> > kernel as one or the other. But noone is suggesting to convert one to
> > the other at boot time.
>
> I was referring to the following line from sd-stub's man page: "The
> following resources are passed as initrd cpio archives to the booted
> kernel: [...] /.extra/sysext/*.raw [...]". I assume the initrd
> containing the sysexts has to be created at some point?

These cpios are created on-the-fly and placed into memory and passed
to the invoked kernel. And yes, for that the data they contian needs
to be read off disk first.

Lennart

--
Lennart Poettering, Berlin