Initial import

flake.lock

@@ -0,0 +1,111 @@
+{
+  "nodes": {
+    "flake-utils": {
+      "inputs": {
+        "systems": "systems"
+      },
+      "locked": {
+        "lastModified": 1710146030,
+        "narHash": "sha256-SZ5L6eA7HJ/nmkzGG7/ISclqe6oZdOZTNoesiInkXPQ=",
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "rev": "b1d9ab70662946ef0850d488da1c9019f3a9752a",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "type": "github"
+      }
+    },
+    "flakey-profile": {
+      "locked": {
+        "lastModified": 1712898590,
+        "narHash": "sha256-FhGIEU93VHAChKEXx905TSiPZKga69bWl1VB37FK//I=",
+        "owner": "lf-",
+        "repo": "flakey-profile",
+        "rev": "243c903fd8eadc0f63d205665a92d4df91d42d9d",
+        "type": "github"
+      },
+      "original": {
+        "owner": "lf-",
+        "repo": "flakey-profile",
+        "type": "github"
+      }
+    },
+    "lix": {
+      "flake": false,
+      "locked": {
+        "lastModified": 1720626042,
+        "narHash": "sha256-f8k+BezKdJfmE+k7zgBJiohtS3VkkriycdXYsKOm3sc=",
+        "rev": "2a4376be20d70feaa2b0e640c5041fb66ddc67ed",
+        "type": "tarball",
+        "url": "https://git.lix.systems/api/v1/repos/lix-project/lix/archive/2a4376be20d70feaa2b0e640c5041fb66ddc67ed.tar.gz"
+      },
+      "original": {
+        "type": "tarball",
+        "url": "https://git.lix.systems/lix-project/lix/archive/2.90.0.tar.gz"
+      }
+    },
+    "lix-module": {
+      "inputs": {
+        "flake-utils": "flake-utils",
+        "flakey-profile": "flakey-profile",
+        "lix": "lix",
+        "nixpkgs": [
+          "nixpkgs"
+        ]
+      },
+      "locked": {
+        "lastModified": 1720641669,
+        "narHash": "sha256-yEO2cGNgzm9x/XxiDQI+WckSWnZX63R8aJLBRSXtYNE=",
+        "rev": "5c48c833c15bb80d127a398a8c2484d42fdd8257",
+        "type": "tarball",
+        "url": "https://git.lix.systems/api/v1/repos/lix-project/nixos-module/archive/5c48c833c15bb80d127a398a8c2484d42fdd8257.tar.gz"
+      },
+      "original": {
+        "type": "tarball",
+        "url": "https://git.lix.systems/lix-project/nixos-module/archive/2.90.0.tar.gz"
+      }
+    },
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1721379653,
+        "narHash": "sha256-8MUgifkJ7lkZs3u99UDZMB4kbOxvMEXQZ31FO3SopZ0=",
+        "owner": "nixos",
+        "repo": "nixpkgs",
+        "rev": "1d9c2c9b3e71b9ee663d11c5d298727dace8d374",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nixos",
+        "ref": "nixos-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "lix-module": "lix-module",
+        "nixpkgs": "nixpkgs"
+      }
+    },
+    "systems": {
+      "locked": {
+        "lastModified": 1681028828,
+        "narHash": "sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768=",
+        "owner": "nix-systems",
+        "repo": "default",
+        "rev": "da67096a3b9bf56a91d16901293e51ba5b49a27e",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-systems",
+        "repo": "default",
+        "type": "github"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}

flake.nix

@@ -0,0 +1,55 @@
+{
+  inputs = {
+    nixpkgs.url = "github:nixos/nixpkgs?ref=nixos-unstable";
+
+    lix-module = {
+      url = "https://git.lix.systems/lix-project/nixos-module/archive/2.90.0.tar.gz";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
+  };
+
+  nixConfig = {
+    extra-substituters = [
+      "https://cache.kyouma.net"
+    ];
+
+    extra-trusted-public-keys = [
+      "cache.kyouma.net:Frjwu4q1rnwE/MnSTmX9yx86GNA/z3p/oElGvucLiZg="
+    ];
+  };
+
+  outputs = { self, nixpkgs, ... }@inputs:
+  let
+    inherit (nixpkgs) lib;
+
+    platforms = builtins.mapAttrs
+      (_: platform: lib.systems.elaborate platform)
+      (import ./platforms.nix);
+
+    modules = [
+      "btrfs" "ephemeral" "iosched" "musl" "ocsp"
+    ];
+  in {
+    overlays.default = import ./overlay.nix;
+    legacyPackages = builtins.mapAttrs (name: platform:
+      import nixpkgs {
+        localSystem = builtins.currentSystem or platform.system;
+        crossSystem = platform;
+        overlays = [ self.overlays.default ];
+      }) platforms;
+
+    nixosModules = lib.genAttrs modules (mod: import ./modules/${mod}.nix inputs)
+      // { default = { ... }: { imports = lib.map (mod: self.nixosModules.${mod}) modules; }; };
+
+    nixosConfigurations = builtins.mapAttrs (_: platform: lib.nixosSystem {
+      specialArgs = { pkgs = self.legacyPackages.${platform.system}; };
+      modules = [ self.nixosModules.default ./nixos.nix ];
+    }) platforms;
+
+    hydraJobs = {
+      nixosConfigurations = builtins.mapAttrs
+        (_: host: host.config.system.build.vm)
+        self.nixosConfigurations;
+    };
+  };
+}

modules/btrfs.nix

@@ -0,0 +1,94 @@
+{ ... }: { config, lib, pkgs, ... }:
+
+let
+  inherit (lib)
+    optionalString
+
+    mkOption
+    types;
+
+  cfg = config.idiosyn.btrfs;
+
+  btrfs-scrub = pkgs.writeShellApplication {
+    name = "btrfs-scrub";
+    runtimeInputs = with pkgs; [ util-linux btrfs-progs ];
+    text = ''
+      findmnt --noheadings --output "SOURCE" --types btrfs --nofsroot | sort -u \
+        | xargs -n 1 -P "$(nproc)" -r btrfs scrub start -B
+    '';
+  };
+
+  btrfs-balance = pkgs.writeShellApplication {
+    name = "btrfs-balance";
+    runtimeInputs = with pkgs; [ util-linux btrfs-progs ];
+    text = ''
+      findmnt --types btrfs --output "SOURCE" --nofsroot --noheading | sort -u \
+        | xargs -n 1 -r findmnt --first-only --noheadings --output "TARGET" --types btrfs --source \
+        | xargs -n 1 -P "$(nproc)" -r btrfs balance start${optionalString (cfg.balance.dataUsage != null) " -dusage=${toString cfg.balance.dataUsage}"}${optionalString (cfg.balance.metadataUsage != null) " -musage=${toString cfg.balance.metadataUsage}"}
+    '';
+  };
+in {
+  options = {
+    idiosyn.btrfs = {
+      scrub.timer = mkOption {
+        type = with types; nullOr nonEmptyStr;
+        default = null;
+        example = "weekly";
+        description = ''
+          Realtime (wallclock) timer for regular scrubs
+
+          See {manpage}systemd.time(7).
+        '';
+      };
+
+      balance = {
+        timer = mkOption {
+          type = with types; nullOr nonEmptyStr;
+          default = null;
+          example = "weekly";
+          description = ''
+            Realtime (wallclock) timer for regular balances.
+
+            See {manpage}systemd.time(7).
+          '';
+        };
+
+        dataUsage = mkOption {
+          type = with types; nullOr (ints.between 0 100);
+          default = 10;
+          description = ''
+            Balance only data block groups with usage below the given percentage.
+          '';
+        };
+
+        metadataUsage = mkOption {
+          type = with types; nullOr (ints.between 0 100);
+          default = 5;
+          description = ''
+            Balance only metadata block groups with usage below the given percentage.
+          '';
+        };
+      };
+    };
+  };
+
+  config = {
+    systemd.services.btrfs-scrub = lib.mkIf (cfg.scrub.timer != null) {
+      startAt = cfg.scrub.timer;
+      unitConfig.ConditionACPower = true;
+      serviceConfig = {
+        Type = "exec";
+        ExecStart = "${btrfs-scrub}/bin/btrfs-scrub";
+      };
+    };
+
+    systemd.services.btrfs-balance = lib.mkIf (cfg.balance.timer != null) {
+      startAt = cfg.balance.timer;
+      unitConfig.ConditionACPower = true;
+      serviceConfig = {
+        Type = "exec";
+        ExecStart = "${btrfs-balance}/bin/btrfs-balance";
+      };
+    };
+  };
+}

modules/ephemeral.nix

@@ -0,0 +1,210 @@
+{ ... }: { config, pkgs, lib, ...}:
+
+with lib; let
+  cfg = config.local.ephemeral;
+
+  device = mkOption {
+    type = types.nonEmptyStr;
+    description = mdDoc "Device to mount.";
+  };
+
+  options = mkOption {
+    type = with types; listOf nonEmptyStr;
+    readOnly = true;
+    description = mdDoc "Options used to mount the file system.";
+  };
+
+  extraOptions = mkOption {
+    type = with types; listOf nonEmptyStr;
+    default = [ ];
+    description = mdDoc "Additional options used to mount the file system.";
+  };
+
+  filesystem = {
+    options = {
+      inherit device options extraOptions;
+      fsType = mkOption {
+        type = types.nonEmptyStr;
+        description = mdDoc "Type of the file system.";
+      };
+    };
+  };
+
+  tmpfs = {
+    options = {
+      inherit options extraOptions;
+      name = mkOption {
+        type = types.nonEmptyStr;
+        default = "none";
+        description = mdDoc "Name of the file system.";
+      };
+
+      size = mkOption {
+        type = with types; either nonEmptyStr ints.positive;
+        description = mdDoc "Size of the file system.";
+      };
+
+      mode = mkOption {
+        type = types.nonEmptyStr;
+        description = mdDoc "Initial permissions of the root directory.";
+      };
+
+      uid = mkOption {
+        type = with types; either nonEmptyStr ints.unsigned;
+        default = 0;
+        description = mdDom "Initial user ID of the root directory";
+      };
+
+      gid = mkOption {
+        type = with types; either nonEmptyStr ints.unsigned;
+        default = 0;
+        description = mdDom "Initial group ID of the root directory";
+      };
+    };
+  };
+
+  subvol = {
+    options = {
+      inherit options extraOptions;
+      subvolume = mkOption {
+        type = with types; nullOr nonEmptyStr;
+        default = null;
+        description = mdDoc "Source path of the subvolume.";
+      };
+    };
+  };
+
+  ephemeralDefaults = {
+    "/" = {
+      size = "256m";
+      mode = "755";
+      uid = 0;
+      gid = 0;
+      options = [ "nodev" "noexec" "nosuid" ];
+      extraOptions = [ ];
+    };
+    "/run/nix" = {
+      size = "80%";
+      mode = "1775";
+      uid = 0;
+      gid = "nixbld";
+      options = [ "nodev" "nosuid" ];
+      extraOptions = [ ];
+    };
+    "/tmp" = {
+      size = "256m";
+      mode = "1777";
+      uid = 0;
+      gid = 0;
+      options = [ "nodev" "noexec" "nosuid" ];
+      extraOptions = [ ];
+    };
+  };
+
+  subvolumeDefaults = {
+    "/etc/keys" = {
+      options = [ "nodev" "noexec" "nosuid" ];
+      extraOptions = [ "noatime" "compress=zstd" ];
+    };
+    "/nix" = {
+      options = [ "nodev" "nosuid" ];
+      extraOptions = [ "noatime" "compress=zstd" ];
+    };
+    "/var" = {
+      options = [ "nodev" "noexec" "nosuid" ];
+      extraOptions = [ "noatime" "compress=zstd" ];
+    };
+  };
+in {
+  options = {
+    local.ephemeral = {
+      enable = mkEnableOption "ephemeral filesystem";
+
+      device = mkOption {
+        type = types.nonEmptyStr;
+        description = mdDoc "Persistent btrfs device.";
+      };
+
+      boot = {
+        inherit device;
+
+        fsType = mkOption {
+          type = types.nonEmptyStr;
+        };
+
+        options = mkOption {
+          inherit (options) type readOnly description;
+          default = [ "nodev" "noexec" "nosuid" ]
+            ++ optionals (cfg.boot.fsType == "vfat") [ "fmask=0137" "dmask=022" ]
+            ++ optionals (builtins.match "ext[34]" cfg.boot.fsType != null) [ "data=journal" ];
+        };
+
+        extraOptions = mkOption {
+          inherit (extraOptions) type description;
+          default = [ "noatime" ];
+        };
+      };
+
+      ephemeral = mkOption {
+        type = with types; attrsOf (submodule tmpfs);
+        description = mdDoc "Ephemeral filesystems.";
+        default = ephemeralDefaults;
+      };
+
+      subvolumes = mkOption {
+        type = with types; attrsOf (submodule subvol);
+        description = mdDoc "Persistent subvolumes.";
+        default = subvolumeDefaults;
+        example = {
+          "/home" = {
+            options = [ "nodev" "noexec" "nosuid" ];
+            extraOptions = [ "noatime" "compress=zstd" ];
+          };
+        };
+      };
+    };
+  };
+
+  config = mkIf cfg.enable {
+    boot.initrd.availableKernelModules = [ "zstd" ];
+    boot.supportedFilesystems = [ "btrfs" ];
+
+    environment.etc.machine-id.source = mkDefault "/etc/keys/machine-id";
+    environment.etc.secureboot.source = mkDefault "/etc/keys/secureboot";
+
+    fileSystems = {
+        "/boot" = mkOverride 99 {
+          device = cfg.boot.device;
+          fsType = cfg.boot.fsType;
+          options = cfg.boot.options ++ cfg.boot.extraOptions;
+        };
+      } //
+      (mapAttrs (key: val: mkOverride 99 {
+        fsType = "tmpfs";
+        options = val.options ++ val.extraOptions
+          ++ [
+            "strictatime"
+            "size=${toString val.size}"
+            "mode=${val.mode}"
+            "uid=${toString val.uid}"
+            "gid=${toString val.gid}"
+            "huge=within_size"
+          ];
+      }) (ephemeralDefaults // cfg.ephemeral)) //
+      (mapAttrs (key: val: mkOverride 99 {
+        device = cfg.device;
+        fsType = "btrfs";
+        options = val.options ++ val.extraOptions
+          ++ [ "subvol=${if (val ? subvolume && val.subvolume != null) then val.subvolume else key}" ];
+        neededForBoot = true;
+      }) (subvolumeDefaults // cfg.subvolumes));
+
+    #nix.settings.build-dir = mkDefault "/run/nix";
+    systemd.services.nix-daemon.environment.TMPDIR = mkDefault "/run/nix";
+
+    systemd.tmpfiles.rules = [
+      "d /etc/keys 0751 root root"
+      "D /run/nix  1775 root nixbld 1d"
+    ];
+  };
+}

modules/iosched.nix

@@ -0,0 +1,118 @@
+{ ... }: { config, lib, pkgs, ... }:
+
+let
+  cfg = config.hardware.block;
+  escape = lib.strings.escape [ ''"'' ];
+
+  inherit (lib)
+    mkIf
+    mkOption
+    types
+
+    concatStrings
+    mapAttrsToList
+    optionalString;
+in {
+  options.hardware.block = {
+    defaultScheduler = mkOption {
+      type = with types; nullOr nonEmptyStr;
+      default = null;
+      description = ''
+        Default block I/O scheduler.
+
+        Unless `null`, the value is assigned through a udev rule matching all
+        block devices.
+      '';
+      example = "kyber";
+    };
+
+    defaultSchedulerRotational = mkOption {
+      type = with types; nullOr nonEmptyStr;
+      default = null;
+      description = ''
+        Default block I/O scheduler for rotational drives (e.g. hard disks).
+
+        Unless `null`, the value is assigned through a udev rule matching all
+        rotational block devices.
+
+        This option takes precedence over
+        {option}`config.hardware.block.defaultScheduler`.
+      '';
+      example = "bfq";
+    };
+
+    scheduler = mkOption {
+      type = with types; attrsOf nonEmptyStr;
+      default = { };
+      description = ''
+        Assign block I/O scheduler by device name pattern.
+
+        Names are matched using the {manpage}`udev(7)` pattern syntax:
+
+        `*`
+        :  Matches zero or more characters.
+
+        `?`
+        :  Matches any single character.
+
+        `[]`
+        :  Matches any single character specified in the brackets. Ranges are
+           supported via the `-` character.
+
+        `|`
+        :  Separates alternative patterns.
+
+
+        Please note that overlapping patterns may produce unexpected results.
+        More complex configurations requiring these should instead be specified
+        directly through custom udev rules, for example via
+        [{option}`config.services.udev.extraRules`](#opt-services.udev.extraRules),
+        to ensure correct ordering.
+
+        Available schedulers depend on the kernel configuration but modern
+        Linux systems typically support:
+
+        `none`
+        :  No‐operation scheduler with no re‐ordering of requests. Suitable
+           for devices with fast random I/O such as NVMe SSDs.
+
+        [`mq-deadline`](https://www.kernel.org/doc/html/latest/block/deadline-iosched.html)
+        :  Simple latency‐oriented general‐purpose scheduler.
+
+        [`kyber`](https://www.kernel.org/doc/html/latest/block/kyber-iosched.html)
+        :  Simple latency‐oriented scheduler for fast multi‐queue devices
+           like NVMe SSDs.
+
+        [`bfq`](https://www.kernel.org/doc/html/latest/block/bfq-iosched.html)
+        :  Complex fairness‐oriented scheduler. Higher processing overhead,
+           but good interactive response, especially with slower devices.
+
+
+        Schedulers assigned through this option take precedence over
+        {option}`config.hardware.block.defaultScheduler` and
+        {option}`config.hardware.block.defaultSchedulerRotational` but may be
+        overridden by other udev rules.
+      '';
+      example = {
+        "mmcblk[0-9]*" = "bfq";
+        "nvme[0-9]*" = "kyber";
+      };
+    };
+  };
+
+  config = mkIf (cfg.defaultScheduler != null ||
+    cfg.defaultSchedulerRotational != null || cfg.scheduler != { }) {
+    services.udev.packages = [
+      (pkgs.writeTextDir "etc/udev/rules.d/98-block-io-scheduler.rules"
+        (optionalString (cfg.defaultScheduler != null) ''
+          SUBSYSTEM=="block", ACTION=="add|change", TEST=="queue/scheduler", ATTR{queue/scheduler}="${escape cfg.defaultScheduler}"
+        '' + optionalString (cfg.defaultSchedulerRotational != null) ''
+          SUBSYSTEM=="block", ACTION=="add|change", ATTR{queue/rotational}=="1", TEST=="queue/scheduler", ATTR{queue/scheduler}="${escape cfg.defaultSchedulerRotational}"
+        '' + concatStrings (mapAttrsToList (name: sched: ''
+          SUBSYSTEM=="block", ACTION=="add|change", KERNEL=="${escape name}", ATTR{queue/scheduler}="${escape sched}"
+        '') cfg.scheduler)))
+    ];
+  };
+
+  meta.maintainers = with lib.maintainers; [ mvs ];
+}

modules/musl.nix

@@ -0,0 +1,15 @@
+{ self, ... }: { config, lib, pkgs, modulesPath, ... }: {
+  disabledModules = [
+    (modulesPath + "/config/ldso.nix")
+    (modulesPath + "/config/stub-ld.nix")
+    (modulesPath + "/programs/nix-ld.nix")
+  ];
+
+  config = lib.mkIf pkgs.stdenv.hostPlatform.isMusl {
+    security.pam.services.login.updateWtmp = lib.mkForce false;
+
+    services.nscd.enable = lib.mkForce false;
+
+    system.nssModules = lib.mkForce [ ];
+  };
+}

modules/ocsp.nix

@@ -0,0 +1,85 @@
+{ ... }: { config, pkgs, lib, ...}:
+
+with lib; let
+  cfg = config.security.acme;
+
+  script = pkgs.writeShellApplication {
+    name = "ocsp-query";
+    runtimeInputs = with pkgs; [ openssl ];
+    text = ''
+      cd "$1"
+
+      tmp="$(mktemp ocsp.der.XXXXXXXXXX)"
+      trap 'rm -f "$tmp"' EXIT TERM
+
+      url="$(openssl x509 -in cert.pem -noout -ocsp_uri)"
+      openssl ocsp -issuer chain.pem -cert cert.pem -url "$url" -respout "$tmp"
+
+      chown "$(id -u):$(id -g)" "$tmp"
+      chmod 644 "$tmp"
+      mv "$tmp" ocsp.der
+
+      ln -s -f ocsp.der full.ocsp
+    '';
+  };
+in {
+  options.security.acme.ocspTimer = mkOption {
+    type = with types; nullOr nonEmptyStr;
+    default = "daily";
+    description = mdDoc "Realtime (wall clock) timer for regular OCSP queries.";
+  };
+
+  config = mkIf (cfg.ocspTimer != null) {
+    systemd.services = mapAttrs' (cert: conf: nameValuePair "ocsp-${cert}" {
+      description = "Query OCSP endpoint for ${cert}";
+      after = [ "network.target" "network-online.target" "acme-${cert}.service" ];
+      wants = [ "network.target" "network-online.target" "acme-${cert}.service" ];
+
+      confinement.enable = true;
+      confinement.packages = with pkgs; [ openssl ];
+
+      serviceConfig = {
+        Type = "oneshot";
+
+        User = "acme";
+        Group = conf.group;
+        UMask = "0022";
+
+        BindPaths = [ conf.directory ];
+
+        ExecStart = "${script}/bin/ocsp-query ${escapeShellArg conf.directory}";
+
+        ProtectProc = "noaccess";
+        ProcSubset = "pid";
+        ProtectHome = true;
+        PrivateTmp = true;
+        PrivateDevices = true;
+        PrivateIPC = true;
+        ProtectHostname = true;
+        ProtectClock = true;
+        ProtectKernelTunables = true;
+        ProtectKernelModules = true;
+        ProtectKernelLogs = true;
+        ProtectControlGroups = true;
+        RestrictAddressFamilies = ["AF_INET" "AF_INET6" ];
+        RestrictNamespaces = true;
+        LockPersonality = true;
+        RestrictRealtime = true;
+        RestrictSUIDSGID = true;
+        RemoveIPC = true;
+        CapabilityBoundingSet = null;
+        NoNewPrivileges = true;
+        SystemCallFilter = [ "@system-service" "~@privileged" "@chown" ];
+        SystemCallArchitectures = "native";
+        DeviceAllow = null;
+        DevicePolicy = "closed";
+        SocketBindDeny = "any";
+      };
+    }) cfg.certs;
+
+    systemd.timers = mapAttrs' (cert: conf: nameValuePair "ocsp-${cert}" {
+      description = "Query OCSP endpoint for ${cert} regularly";
+      timerConfig.OnCalendar = cfg.ocspTimer;
+    }) cfg.certs;
+  };
+}

modules/thinlto.nix

@@ -0,0 +1,92 @@
+{ ... }: { config, lib, ... }:
+
+let
+  cfg = config.nix.thinlto;
+
+  timespan = lib.mkOptionType {
+    name = "Time span";
+    check = v: lib.isString v && builtins.match "([1-9][0-9]* ?(µs|[um]s(ec)?|s(ec(onds?)?)?|m(in(utes?)?)?|h(ours?)?|d(ays?)?|w(eeks?)?|months?|M|y(years?)?)( |$)?)+" v;
+    merge = lib.mergeEqualOptions;
+  };
+in {
+  options.nix.thinlto = {
+    cacheDir = lib.mkOption {
+      type = lib.types.path;
+      description = "ThinLTO cache directory";
+      default = "/var/cache/thinlto";
+    };
+
+    cacheDirSandbox = lib.mkOption {
+      type = lib.types.path;
+      description = "ThinLTO cache directory in sandbox";
+      default = "/cache/thinlto";
+      readonly = true;
+    };
+
+    owner = lib.mkOption {
+      type = lib.types.nonEmptyStr;
+      description = "Owner of the ThinLTO cache directory";
+      default = "root";
+    };
+
+    group = lib.mkOption {
+      type = lib.types.nonEmptyStr;
+      description = "Group owner of the ThinLTO cache directory";
+      default = "nixbld";
+    };
+
+    expiry = lib.mkOption {
+      type = with lib.types; nullOr timespan;
+      description = "ThinLTO cache expiration age";
+      default = "90d";
+    };
+
+    config = {
+      nix.settings.extra-sandbox-paths = [ "${cfg.cacheDirSandbox}=${cfg.cacheDir}" ];
+
+      nixpkgs.overlays = [(final: prev:
+        let
+          inherit (final) addAttrsToDerivation optional;
+        in {
+          useThinLTO = stdenv: if stdenv.cc.isClang && stdenv.cc.bintools.isLLVM
+            then addAttrsToDerivation (args: {
+              env = (args.env or { }) // {
+                NIX_CFLAGS_COMPILE = toString (optional (args ? env.NIX_CFLAGS_COMPILE) args.env.NIX_CFLAGS_COMPILE
+                  ++ [ "-flto=thin" ]);
+              };
+
+              NIX_CFLAGS_LINK = (optional (args ? NIX_CFLAGS_LINK) args.NIX_CFLAGS_LINK)
+                ++ [ "-Wl,--thinlto-cache-dir=${cfg.cacheDirSandbox}" ];
+              NIX_LDFLAGS = (optional (args ? NIX_LDFLAGS) args.NIX_LDFLAGS)
+                ++ [ "--thinlto-cache-dir=${cfg.cacheDirSandbox}" ];
+              NIX_RUSTFLAGS = (optional (args ? NIX_RUSTFLAGS) args.NIX_RUSTFLAGS)
+                ++ [ "-C lto=thin" "-C linker-plugin-lto=true" "-C link-arg=--thinlto-cache-dir=${cfg.cacheDirSandbox}" ];
+            }) stdenv
+            else builtins.trace "ThinLTO requires Clang and LLD" stdenv;
+      })];
+
+      nixpkgs.config = {
+        replaceStdenv = lib.mkDefault ({ pkgs }:
+          let
+            inherit (pkgs) overrideCC stdenv useThinLTO;
+            inherit (pkgs.llvmPackages_latest) clangUseLLVM;
+          in useThinLTO (overrideCC stdenv clangUseLLVM));
+
+        replaceCrossStdenv = lib.mkDefault ({ buildPackages, baseStdenv }:
+          let
+            inherit (buildPackages) overrideCC;
+            inherit (buildPackages.llvmPackages_latest) clangUseLLVM;
+          in overrideCC baseStdenv clangUseLLVM);
+      };
+
+      systemd.tmpfiles.settings = {
+        ${cfg.cacheDir}.q = {
+          user = cfg.owner;
+          group = cfg.group;
+          mode = "2770";
+          age = lib.mkIf (cfg.expiry != null) cfg.expiry;
+        };
+      };
+    };
+  };
+}

nixos.nix

@@ -0,0 +1,22 @@
+{ pkgs, ... }: {
+  boot.loader.systemd-boot.enable = true;
+  boot.loader.efi.canTouchEfiVariables = true;
+
+  fileSystems."/".label = "nixos";
+
+  nixpkgs = { inherit pkgs; };
+
+  security.sudo.wheelNeedsPassword = false;
+  services.getty.autologinUser = "nixos";
+
+  users.users.nixos = {
+    isNormalUser = true;
+    extraGroups = [ "wheel" ];
+  };
+
+  system.stateVersion = "24.11";
+
+  virtualisation.vmVariant.virtualisation.diskImage = null;
+
+  hardware.block.defaultScheduler = "kyber";
+}

overlay.nix

@@ -0,0 +1,21 @@
+final: prev:
+let
+  inherit (final) lib callPackage;
+in {
+  glibcLocales = callPackage (prev.path + "/pkgs/development/libraries/glibc/locales.nix")  { };
+
+  keyutils = prev.keyutils.overrideAttrs (args: {
+    buildFlags = args.buildFlags or [ ]
+      ++ lib.optional final.keyutils.stdenv.cc.bintools.isLLVM "LDFLAGS=-Wl,--undefined-version";
+  });
+
+  cpp-utilities = prev.cpp-utilities.overrideAttrs (args: {
+    buildInputs = [ final.boost ];
+  });
+
+  time = prev.time.overrideAttrs (args: {
+    env = args.env or { } // {
+      NIX_CFLAGS_COMPILE = toString (lib.optional (args ? env.NIX_CFLAGS_COMPILE) args.env.NIX_CFLAGS_COMPILE ++ [ "--include=<string.h>" ]);
+    };
+  });
+}

platforms.nix

@@ -0,0 +1,8 @@
+{
+  "x86_64-linux" = {
+    config = "x86_64-unknown-linux-musl";
+    gcc.arch = "x86-64-v3";
+    useLLVM = true;
+    linker = "lld";
+  };
+}