Kernels and initrds on the ESP are now content-addressed. By definition,
it is impossible for two different kernels or initrds to ever end up at
the same place, even in the presence of changing initrd secrets or other
unreproducibility.
The basic advantage of this is that installing the kernel or initrd for
a generation can never break another generation. In turn, this enables
the following two improvements:
* All generations can be installed independently. In particular, the
installation can be performed in one pass, one generation at a time.
As a result, the code is significantly simplified, and memory usage
(due to the temporary files) does not grow with the number of
generations any more.
* Generations that already have their files in place on the ESP do not
need to be reinstalled. This will be taken advantage of in a
subsequent commit.
Architecture is now a generic structure that can be specialized
via an "external" trait for generating the paths you care about
depending on your target bootloader.
systemd-boot is now installed once for many generations rather than multiple times.
This means it is not really possible to manage different system in the same "machine", which is a very
obscure usecase, theoretically possible, but not yet encountered.
We will hard fail in case of encountering different architectures in bootspec.
This should still be compatible with cross-compiling systems in the future.
This generates `lzbt-systemd` binary instead of `lzbt`
which is using a special systemd-specific entrypoint.
This is part of the effort to enable multiple backends.
Bootspec has a mechanism called synthesis where you can synthesize
bootspecs if they are not present based on the generation link only.
This is useful for "vanilla bootspec" which does not contain any
extensions, as this is what we do right now.
If we need extensions, we can also implement our synthesis mechanism on
the top of it.
Enabling synthesis gives us the superpower to support non-bootspec
users. :-)
The message about malformed generatiosn should semantically be a
warning. However, since users might have hundres of old and thus
malformed generations and can do little about it, this should remain a
debug message. This way the user is not spammed with no-op warnings
while still enabling debugging.
lzbt currently happily nukes all boot entries, if it can't parse any
bootspecs. With the upcoming incompatible bootspec change, this might
be a problem that's worth avoiding. :)
I changed lzbt to fail hard in case, it can't generate any boot
items.
Alois Wohlschlager