92 lines
4.0 KiB
Nix
92 lines
4.0 KiB
Nix
{ config, lib, pkgs, ... }:
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{
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nix.settings = {
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# see: `man nix.conf`
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# useful when a remote builder has a faster internet connection than me.
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# note that this also applies to `nix copy --to`, though.
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# i think any time a remote machine wants a path, this means we ask them to try getting it themselves before we supply it.
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builders-use-substitutes = true; # default: false
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# maximum seconds to wait when connecting to binary substituter
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connect-timeout = 3; # default: 0
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# download-attempts = 5; # default: 5
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# allow `nix flake ...` command
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experimental-features = [ "nix-command" "flakes "];
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# whether to build from source when binary substitution fails
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fallback = true; # default: false
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# whether to keep building dependencies if any other one fails
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keep-going = true; # default: false
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# whether to keep build-only dependencies of GC roots (e.g. C compiler) when doing GC
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keep-outputs = true; # default: false
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# how many lines to show from failed build
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log-lines = 30; # default: 10
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# how many substitution downloads to perform in parallel.
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# i wonder if parallelism is causing moby's substitutions to fail?
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max-substitution-jobs = 6; # default: 16
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# narinfo-cache-negative-ttl = 3600 # default: 3600
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# whether to use ~/.local/state/nix/profile instead of ~/.nix-profile, etc
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use-xdg-base-directories = true; # default: false
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# whether to warn if repository has uncommited changes
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warn-dirty = false; # default: true
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# hardlinks identical files in the nix store to save 25-35% disk space.
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# unclear _when_ this occurs. it's not a service.
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# does the daemon continually scan the nix store?
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# does the builder use some content-addressed db to efficiently dedupe?
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auto-optimise-store = true;
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# allow #!nix-shell scripts to locate my patched nixpkgs & custom packages.
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# this line might become unnecessary: see <https://github.com/NixOS/nixpkgs/pull/273170>
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nix-path = config.nix.nixPath;
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};
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# allow `nix-shell` (and probably nix-index?) to locate our patched and custom packages.
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# this is actually a no-op, and the real action happens in assigning `nix.settings.nix-path`.
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nix.nixPath = (lib.optionals config.sane.enableSlowPrograms [
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"nixpkgs=${pkgs.path}"
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]) ++ [
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# note the import starts at repo root: this allows `./overlay/default.nix` to access the stuff at the root
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# "nixpkgs-overlays=${../../..}/hosts/common/nix-path/overlay"
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# as long as my system itself doesn't rely on NIXPKGS at runtime, we can point the overlays to git
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# to avoid switching so much during development
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"nixpkgs-overlays=/home/colin/dev/nixos/hosts/common/nix/overlay"
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];
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# ensure new deployments have a source of this repo with which they can bootstrap.
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# this however changes on every commit and can be slow to copy for e.g. `moby`.
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environment.etc."nixos" = lib.mkIf config.sane.enableSlowPrograms {
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source = ../../..;
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};
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environment.etc."nix/registry.json" = lib.mkIf (!config.sane.enableSlowPrograms) {
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enable = false;
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};
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systemd.services.nix-daemon.serviceConfig = {
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# the nix-daemon manages nix builders
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# kill nix-daemon subprocesses when systemd-oomd detects an out-of-memory condition
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# see:
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# - nixos PR that enabled systemd-oomd: <https://github.com/NixOS/nixpkgs/pull/169613>
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# - systemd's docs on these properties: <https://www.freedesktop.org/software/systemd/man/systemd.resource-control.html#ManagedOOMSwap=auto%7Ckill>
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#
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# systemd's docs warn that without swap, systemd-oomd might not be able to react quick enough to save the system.
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# see `man oomd.conf` for further tunables that may help.
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#
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# alternatively, apply this more broadly with `systemd.oomd.enableSystemSlice = true` or `enableRootSlice`
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# TODO: also apply this to the guest user's slice (user-1100.slice)
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# TODO: also apply this to distccd
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ManagedOOMMemoryPressure = "kill";
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ManagedOOMSwap = "kill";
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};
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}
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