This change does two things:
* "NixOSizes" environment variables generation. This allows some more
error-checking and opens possibilities for a modular environment
configuration. From now on the most of environment variables are
generated directly by the nix code. Generating sh code that
generates environment variables is left in a few places where
nontrivial access to a local environment state is needed.
* By doing the first change this patch untangles bash from the
environment configuration and makes it trivial to add a support for
other non bash-compatible shells.
Now to the sad part. This change is quite large (and I'm not sure it's
possible to split it) and yet is not quite complete, it needs some
changes to nixpkgs to be perfect.
See !!! comments in modules/config/shells-environment.nix.
Main principle behind this change is "change environment generation
and nothing else". In particular, shell configuration principles stay
exactly the same as before.
Also, slightly change the shebang fixup in the patchPhase so that it
handles optional [[:space:]] before the interpreter path (needed for the
filters).
To enable the extra filters, put this in packageOverrides:
asciidoc = pkgs.asciidoc.override {
enableDitaaFilter = true;
enableMscgenFilter = true;
enableDiagFilter = true;
};
This didn't work reliably because it raced with the remounting of /.
So if you were unlucky, then / was read-only by the time we ran
"alsactl store". Now the sound card state is saved before anything is
unmounted/remounted.
The services systemd-random-seed-save.service and
systemd-update-utmp-shutdown.service from systemd 203 don't work,
because they have a RequiresMountFor dependency on /var/lib and
/var/log. Such a dependency produces a cycle, causing systemd to drop
those services:
Fixing conflicting jobs by deleting job poweroff.target/stop
Deleting job systemd-poweroff.service/stop as dependency of job poweroff.target/stop
Deleting job umount.target/stop as dependency of job systemd-poweroff.service/stop
Deleting job -.mount/start as dependency of job umount.target/stop
Deleting job systemd-random-seed-save.service/start as dependency of job -.mount/start
Deleting job systemd-update-utmp-shutdown.service/start as dependency of job -.mount/start
Dropping the RequiresMountFor doesn't work either, because then
/var/... may have meen unmounted or remounted read-only.
Upstream systemd fixes this by doing the actual work from an ExecStop
action in an already-running service than conflicts with
shutdown.target. So I backported that here. The main consequence is
that wtmp shutdown records now get written properly.
The main lesson: shutdown.target is useless for pulling in services
during shutdown if they need to write anywhere.
