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.
We introduce `linux-bootloader` a crate made to build Rust-based Linux-oriented bootloaders.
It follows systemd/UAPI group and semantics as much as possible, e.g. BLS/loader capabilities/stub capabilities.
A compile time feature is introduced that allows to build "fat" stubs
that can be used to build "fat" UKIs. "fat" here means that the actual
kernel and initrd are embedded in the PE binary, not only the file path
and hash. This brings us one step closer to feature partiy with
systemd-stub and thus one step closer to replacing it fully. Such a
"fat" or "real" UKI is also interesting for image-based deployments of
NixOS.
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.
People reportedly want to compile the stub on i686 and AArch64
platforms for testing. Make compilation possible by providing proper
`make_instruction_cache_coherent` implementations on these platforms.
For x86 (just as x86_64), this is a no-op, because Intel made the
instruction cache coherent for compatibility with code that was written
before caches existed.
For AArch64, adapt the procedure from their manual to multiple
instructions.
... because this might not work, if we were not loaded from a file
system. It also removes the issue where we might not load the signed
image that was actually loaded.
Fixes#123
Due to the use of hash maps, the order of file installation was not
deterministic. I've changed the code the use BTreeMaps instead, which
makes this deterministic. While I was here, I tried to simplify the
code a bit.
To minimize writes to the ESP but still find necessary changes, compare
the hashes of the files on the ESP with the "expected" hashes. Only copy
and overwrite already existing files if the hashes don't match. This
ensures a working-as-expected state on the ESP as opposed to previously
where already existing files were just ignored.
Previously, generations were installed one after another. Now all
artifacts (kernels, initrd etc.) are first collected and then installed.
This way the writes to the ESP are reduced as duplicate paths are
already removed in the collection phase.
Using random names for tempfiles makes handling them easier. It reduces
the amount of noise in the code because no custom name needs to be
provided for each tempfile. The names were not really useful in any
case.
It also does not burden the developer with ensuring uniqueness of names.
This is relevant when files for multiple generations need to be stored
in the same directory (e.g. because they need to be accessed after
handling one generation).
Out of an abundance of caution, 32 random alphanumeric characters are
chosen for each filename. The tempfile crate, in comparison, only
chooses 8. 32 characters should be enough to avoid collisions, even
if the PRNG is not of cryptographic quality.
Leverage the bootspec `label` field in its intended way. The VERSION_ID
of the os-release in the stub now only contains the generation number
and the build time. This makes a correct PRETTY_NAME entirely dependent
on correct information in the bootspec `label` field.
Read the build time from generation symlinks in /nix/var/nix/profiles
instead of from the underlying derivation. The derivation build time
will always be a UNIX epoch of 0 because of the `nix-build` sandbox,
which is useless for identifying when a generation was created.
Alois Wohlschlager