Hermetic-usr implementation on dracut

[Emanuele Giuseppe Esposito <eesposit@xxxxxxxxxx>]

Hello everyone,

As you might know already, I tried to submit a new dracut module that
implements the hermetic-usr approach described by Lennart in his
blogpost "Fitting everything together":
https://0pointer.net/blog/fitting-everything-together.html.

The PR is here: https://github.com/dracut-ng/dracut-ng/pull/1234

While there are some small things to fix, it works well, at least in the
environments that I tried.

It is able to recreate the whole root from scratch, provided that /usr
is existing in a separate partition.It creates a LUKS as well as
plaintext root, and supports plaintext /usr as well as dm-verity
protected one.

Zbigniew pointed me that a dracut module might not be the best way to
achieve this, and there might be work in progress already in systemd to
achieve the same goal with a separate systemd component.

Can you point me to the work that is being done in systemd? More
specifically, if there is something similar to what I implemented that
puts together systemd-repart with systemd-tmpfiles and sysusers and
creates a root. Is there some project already going on that does this?

My module uses only 3 systemd units, and most of this stuff could be
reused, if you want. Or maybe is it better to continue the work on dracut?

Let me know,
Emanuele