This version should have more conventional regexes that work across many
platforms and regex engines. This is an issue because up until Nix 1.11,
Nix called out to the libc regex matcher, which behaved differently on
Darwin and Linux. And in Nix 1.12, we're moving to std::regex which will
also behave differently here.
And yes, I do actually evaluate make-disk-image.nix on Darwin ;)
Due the recent inclusion of broadcom-bt-firmware in enableAllFirmware,
it was required to set `nixpkgs.config.allowUnfree` to obtain the full
list. To make this dependency more explicit an assertion is added and an
alternative option `enableRedistributalFirmware` is provided to only
obtain firmware with an license allowing redistribution.
This changes much of the make-disk-image.nix logic (and thus most NixOS
image building) to use LKL to set up the target directory structure rather
than a Linux VM. The only work we still do in a VM is less IO-heavy stuff
that while still time-consuming, is less of the overall load. The goal is
to kill more of that stuff, but that will require deeper changes to NixOS
activation scripts and switch-to-configuration.pl, and I don't want to
bite off too much at once.
The key distinction I'm drawing is that there's a component that deals
with the store of the machine being built, and another component for
the store building it. The inner part of it assumes nothing from the
builder (doesn't need chroot or root powers) so it can run comfortably
inside a Nix build, as well as nixos-rebuild. I have some upcoming work
that will use that to significantly speed up and streamline image builds
for NixOS, especially on virtualized hosts like EC2, but it's also a
reasonable speedup on native hosts.
Currently, if you try to build a NixOS config including channel.nix, e.g.:
nix-build -I nixpkgs=. -I nixos-config=nixos/modules/installer/cd-dvd/installation-cd-minimal.nix nixos -A config.system.build.isoImage
twice in a row, you end up with two different build results. This is
caused by the 'result' symlink of the first build affecting the channel
contents of the second build.
If we use filterSource with a predicate that ignores the 'result'
symlinks, the problem is gone. Do the same thing for VIM/Emacs
swap/backup files to avoid even more 'spurious' rebuilds.
Additionally, filter out the '.git' directory at the same time, as we
'rm -rf' it from the result anyway. This avoids a considerable amount of
unnecessary file I/O copying and deleting the .git directory.
Turns out all variants of start.elf and fixup.dat are needed (depending
on what's in config.txt). I was under the mistaken impression that you
were supposed to rename one of the variants to switch using them, but
nope.
