From 109c57708461d74a14dc372e7e40a2d52566aef4 Mon Sep 17 00:00:00 2001
From: catvayor <catvayor@katvayor.net>
Date: Mon, 30 Sep 2024 16:39:58 +0200
Subject: [PATCH 1/8] systemd override

---
 default.nix            |  2 +-
 modules/s6/default.nix |  5 ++-
 overlay.nix            | 97 +++++++++++++++++++++++++++++++++++++++++-
 3 files changed, 101 insertions(+), 3 deletions(-)

diff --git a/default.nix b/default.nix
index fd1c357..a456110 100644
--- a/default.nix
+++ b/default.nix
@@ -57,7 +57,7 @@ let
     ];
   }).config.system;
 in {
-  inherit evalModules;
+  inherit evalModules config;
 
   outputs = config.system.outputs // {
     default = config.system.outputs.${config.hardware.defaultOutput};
diff --git a/modules/s6/default.nix b/modules/s6/default.nix
index e1ce9c8..376d4ce 100644
--- a/modules/s6/default.nix
+++ b/modules/s6/default.nix
@@ -186,8 +186,11 @@ in {
           };
         };
       };
+      # bin = dir {
+      #   init = symlink "${s6-init-bin}/bin/init";
+      # };
       bin = dir {
-        init = symlink "${s6-init-bin}/bin/init";
+        init = symlink "${pkgs.systemd}/bin/init";
       };
     };
   };
diff --git a/overlay.nix b/overlay.nix
index 891e9a0..be76616 100644
--- a/overlay.nix
+++ b/overlay.nix
@@ -259,7 +259,7 @@ extraPkgs // {
     patches = o.patches ++ [
       ./pkgs/qemu/arm-image-friendly-load-addr.patch
     ];
-  }); in q.override { nixosTestRunner = true; sdlSupport = false; };
+  }); in q.override { nixosTestRunner = true; sdlSupport = false; hostCpuTargets = [ "mips-softmmu" ]; };
 
   rsyncSmall =
     let r = prev.rsync.overrideAttrs(o: {
@@ -284,6 +284,101 @@ extraPkgs // {
 
   strace = prev.strace.override { libunwind = null; };
 
+  getent =
+    prev.callPackage ({
+      lib,
+      stdenv,
+      fetchFromGitHub,
+    }:
+
+    stdenv.mkDerivation rec {
+      pname = "musl-utils";
+      version = "1.1.12-r7";
+
+      src = fetchFromGitHub {
+        owner = "boltlinux";
+        repo = "musl-utils";
+        rev = version;
+        hash = "sha256-q9CbOyK0Psw3YJnIT3yPRWuwr40nxLZt4RexuOHAUuw=";
+      };
+
+      nativeBuildInputs = [
+        prev.autoconf
+        prev.automake
+      ];
+
+      preConfigure = ''
+        autoreconf -i
+      '';
+
+      buildPhase = ''
+        make -C src getent
+      '';
+
+      installPhase = ''
+        mkdir -p $out/bin/
+        cp src/getent $out/bin/
+      '';
+
+      meta = {
+        description = "Alpine Linux' getconf, getent and iconv implementations";
+        homepage = "https://github.com/boltlinux/musl-utils";
+        license = lib.licenses.free; # FIXME: nix-init did not find a license
+        maintainers = with lib.maintainers; [ ];
+        mainProgram = "musl-utils";
+        platforms = lib.platforms.all;
+      };
+    }) { };
+
+  systemd = prev.systemd.override {
+    withAcl = false;
+    withAnalyze = false;
+    withApparmor = false;
+    withAudit = false;
+    withBootloader = false;
+    # withCompression = true;
+    withCoredump = false;
+    withCryptsetup = false;
+    withRepart = false;
+    withDocumentation = false;
+    withEfi = false;
+    withFido2 = false;
+    withHomed = false;
+    # withHostnamed = true;
+    withHwdb = false;
+    withImportd = false;
+    withIptables = false;
+    withKmod = false;
+    withLibBPF = false;
+    withLibidn2 = false;
+    withLocaled = false;
+    # withLogind = true;
+    withMachined = false;
+    # withNetworkd = true;
+    withNss = false;
+    withOomd = false;
+    # withPam = true;
+    # withPasswordQuality = true;
+    withPCRE2 = false;
+    withPolkit = false;
+    withPortabled = false;
+    withQrencode = false;
+    withRemote = false;
+    # withResolved = true;
+    # withShellCompletions = true;
+    # withSysusers = true;
+    withSysupdate = false;
+    # withTimedated = true;
+    # withTimesyncd = true;
+    withTpm2Tss = false;
+    withUkify = false;
+    withUserDb = false;
+    withUtmp = false;
+    withVmspawn = false;
+    withKernelInstall = false;
+    withLibarchive = false;
+  };
+
   ubootQemuAarch64 = final.buildUBoot {
     defconfig = "qemu_arm64_defconfig";
     extraMeta.platforms = ["aarch64-linux"];
-- 
2.47.0


From ae78f9aafd872af9ff53c1fb040b8e331faa69fd Mon Sep 17 00:00:00 2001
From: catvayor <catvayor@katvayor.net>
Date: Mon, 30 Sep 2024 19:38:13 +0200
Subject: [PATCH 2/8] systemd init

---
 lib/eval-config.nix                  |  2 +-
 modules/base.nix                     |  3 +--
 modules/s6/scripts/rc.shutdown       | 19 -------------------
 modules/s6/scripts/rc.shutdown.final | 22 ----------------------
 modules/s6/scripts/runlevel          | 12 ------------
 modules/systemd/default.nix          | 25 +++++++++++++++++++++++++
 overlay.nix                          | 10 +++++-----
 7 files changed, 32 insertions(+), 61 deletions(-)
 delete mode 100755 modules/s6/scripts/rc.shutdown
 delete mode 100755 modules/s6/scripts/rc.shutdown.final
 delete mode 100755 modules/s6/scripts/runlevel
 create mode 100644 modules/systemd/default.nix

diff --git a/lib/eval-config.nix b/lib/eval-config.nix
index 4c3c009..986e9d5 100644
--- a/lib/eval-config.nix
+++ b/lib/eval-config.nix
@@ -14,7 +14,7 @@ in
     "${modulesPath}/busybox.nix"
     "${modulesPath}/hostname.nix"
     "${modulesPath}/kernel"
-    "${modulesPath}/s6"
+    "${modulesPath}/systemd"
     "${modulesPath}/users.nix"
     "${modulesPath}/outputs.nix"
     "${modulesPath}/nixpkgs.nix"
diff --git a/modules/base.nix b/modules/base.nix
index 5107e1e..30141a8 100644
--- a/modules/base.nix
+++ b/modules/base.nix
@@ -129,10 +129,9 @@ in {
     # By default, we enable cross-compilation support.
     nixpkgs.buildPlatform = lib.mkDefault builtins.currentSystem;
 
-    defaultProfile.packages = with pkgs;
-      [ s6 s6-init-bin execline s6-linux-init s6-rc ];
     # Set the useful PS1 prompt by default.
     defaultProfile.environmentVariables.PS1 = lib.mkDefault config.defaultProfile.prompt;
+    defaultProfile.packages = with pkgs; [ execline ];
 
     boot.commandLine = [
       "panic=10 oops=panic init=/bin/init loglevel=8"
diff --git a/modules/s6/scripts/rc.shutdown b/modules/s6/scripts/rc.shutdown
deleted file mode 100755
index 81fac67..0000000
--- a/modules/s6/scripts/rc.shutdown
+++ /dev/null
@@ -1,19 +0,0 @@
-#!/bin/sh
-
-
-### Things to do before hardware halt/reboot/poweroff.
-### Ideally, it should be a single call to the service manager,
-### telling it to bring all the services down.
-
-### If your s6-linux-init-maker invocation was made with the -1
-### option, messages from rc.shutdown will appear on /dev/console
-### as well as be logged by the catch-all logger.
-### If your s6-linux-init-maker invocation did NOT include the -1
-### option, messages from rc.shutdown will only be logged by the
-### catch-all logger and will NOT appear on /dev/console. In order
-### to print them to /dev/console instead, you may want to
-### uncomment the following line:
-exec >/dev/console 2>&1
-
-### If your services are managed by s6-rc:
-exec s6-rc -v2 -bDa change
diff --git a/modules/s6/scripts/rc.shutdown.final b/modules/s6/scripts/rc.shutdown.final
deleted file mode 100755
index 5344b7a..0000000
--- a/modules/s6/scripts/rc.shutdown.final
+++ /dev/null
@@ -1,22 +0,0 @@
-#!/bin/sh -e
-
-##  s6-linux-init-shutdownd never tells s6-svscan to exit, so if
-##  you're running s6-linux-init, it's normal that your
-##  .s6-svscan/finish script is not executed.
-
-##  The place where you want to hack things is /etc/rc.shutdown.final,
-##  which is run by the stage 4 script right before the hard reboot.
-##  So you can do dirty stuff [...] which should clean up the
-##  s6-supervise and the foreground, and give control to
-##  .s6-svscan/finish.
-
-## -- Laurent Bercot on skaware mailing list,
-##    https://skarnet.org/lists/skaware/1913.html
-
-exec >/dev/console 2>&1
-
-# down, exit supervisor, wait, stay down
-s6-svc -dxwD /run/service/s6-linux-init-shutdownd
-# HUP, exit supervisor, wait, down
-s6-svc -hxwd /run/service/s6-svscan-log
-s6-svscanctl -b /run/service # abort
diff --git a/modules/s6/scripts/runlevel b/modules/s6/scripts/runlevel
deleted file mode 100755
index 3c2cfcd..0000000
--- a/modules/s6/scripts/runlevel
+++ /dev/null
@@ -1,12 +0,0 @@
-#!/bin/sh -e
-
-### This script is called once at boot time by rc.init, and is
-### also called by the runleveld service every time the user
-### requests a machine state change via telinit.
-### Ideally, it should just be a call to the service manager.
-
-test "$#" -gt 0 || { echo 'runlevel: fatal: too few arguments' 1>&2 ; exit 100 ; }
-
-
-### If your services are managed by s6-rc:
-exec s6-rc -v2 -up change "$1"
diff --git a/modules/systemd/default.nix b/modules/systemd/default.nix
new file mode 100644
index 0000000..7f6c1dc
--- /dev/null
+++ b/modules/systemd/default.nix
@@ -0,0 +1,25 @@
+{ pkgs, ... }:
+let
+  inherit (pkgs.pseudofile) dir symlink;
+in
+{
+  config = {
+    boot.commandLine = [
+      "systemd.log_level=7"
+      #"systemd.crash_shell=true"
+    ];
+    filesystem = dir {
+      etc = dir {
+        systemd = dir {
+          "system.conf" = {
+            file = '''';
+            mode = "0444";
+          };
+        };
+      };
+      bin = dir {
+        init = symlink "${pkgs.systemd}/bin/init";
+      };
+    };
+  };
+}
diff --git a/overlay.nix b/overlay.nix
index be76616..74327e2 100644
--- a/overlay.nix
+++ b/overlay.nix
@@ -352,19 +352,19 @@ extraPkgs // {
     withLibBPF = false;
     withLibidn2 = false;
     withLocaled = false;
-    # withLogind = true;
+    withLogind = false;
     withMachined = false;
-    # withNetworkd = true;
+    withNetworkd = false;
     withNss = false;
     withOomd = false;
-    # withPam = true;
-    # withPasswordQuality = true;
+    withPam = false;
+    withPasswordQuality = false;
     withPCRE2 = false;
     withPolkit = false;
     withPortabled = false;
     withQrencode = false;
     withRemote = false;
-    # withResolved = true;
+    withResolved = false;
     # withShellCompletions = true;
     # withSysusers = true;
     withSysupdate = false;
-- 
2.47.0


From 8c97f3e2571bb6952cb88771ca14f47b6ba15e10 Mon Sep 17 00:00:00 2001
From: catvayor <catvayor@katvayor.net>
Date: Tue, 1 Oct 2024 11:00:15 +0200
Subject: [PATCH 3/8] agetty

---
 modules/systemd/default.nix | 49 ++++++++++++++++++++++++++++++++++---
 1 file changed, 46 insertions(+), 3 deletions(-)

diff --git a/modules/systemd/default.nix b/modules/systemd/default.nix
index 7f6c1dc..7b28730 100644
--- a/modules/systemd/default.nix
+++ b/modules/systemd/default.nix
@@ -1,9 +1,53 @@
 { pkgs, ... }:
 let
   inherit (pkgs.pseudofile) dir symlink;
+  "getty.service" = {
+    file =
+    let
+      login = pkgs.writeScript "login" ''
+        #!/bin/ash
+        exec /bin/ash
+      '';
+    in
+    ''
+      [Unit]
+      Description="Serial shell"
+
+      [Service]
+      ExecStart=${pkgs.util-linux}/bin/agetty --login-program ${login} ttyS0
+    '';
+    mode = "0644";
+  };
+  "default.target" = {
+    file = ''
+      [Unit]
+      Description="target to boot"
+      Wants=getty.service
+      After=getty.service
+      AllowIsolate=yes
+    '';
+  };
+  "sysinit.target" = {
+    file = ''
+      [Unit]
+      Description="sysinit.target"
+    '';
+  };
 in
 {
   config = {
+    kernel.config = {
+      CGROUPS = "y";
+      DEVTMPFS = "y";
+      INOTIFY_USER = "y";
+      SIGNALFD = "y";
+      TIMERFD = "y";
+      EPOLL = "y";
+      UNIX = "y";
+      SYSFS = "y";
+      PROC_FS = "y";
+      FHANDLE = "y";
+    };
     boot.commandLine = [
       "systemd.log_level=7"
       #"systemd.crash_shell=true"
@@ -11,9 +55,8 @@ in
     filesystem = dir {
       etc = dir {
         systemd = dir {
-          "system.conf" = {
-            file = '''';
-            mode = "0444";
+          system = dir {
+            inherit "default.target" "getty.service" "sysinit.target";
           };
         };
       };
-- 
2.47.0


From 14b59b5b6209ed195e496f558781d46a9f1a9142 Mon Sep 17 00:00:00 2001
From: catvayor <catvayor@katvayor.net>
Date: Tue, 1 Oct 2024 16:43:53 +0200
Subject: [PATCH 4/8] begin minimization of systemd

trivial part
---
 overlay.nix | 160 ++++++++++++++++++++++++++++++++++++----------------
 1 file changed, 111 insertions(+), 49 deletions(-)

diff --git a/overlay.nix b/overlay.nix
index 74327e2..1e9b150 100644
--- a/overlay.nix
+++ b/overlay.nix
@@ -259,7 +259,12 @@ extraPkgs // {
     patches = o.patches ++ [
       ./pkgs/qemu/arm-image-friendly-load-addr.patch
     ];
-  }); in q.override { nixosTestRunner = true; sdlSupport = false; hostCpuTargets = [ "mips-softmmu" ]; };
+  }); in q.override {
+    vde2 = null;
+    nixosTestRunner = true;
+    sdlSupport = false;
+    hostCpuTargets = [ "mips-softmmu" ];
+  };
 
   rsyncSmall =
     let r = prev.rsync.overrideAttrs(o: {
@@ -330,54 +335,111 @@ extraPkgs // {
       };
     }) { };
 
-  systemd = prev.systemd.override {
-    withAcl = false;
-    withAnalyze = false;
-    withApparmor = false;
-    withAudit = false;
-    withBootloader = false;
-    # withCompression = true;
-    withCoredump = false;
-    withCryptsetup = false;
-    withRepart = false;
-    withDocumentation = false;
-    withEfi = false;
-    withFido2 = false;
-    withHomed = false;
-    # withHostnamed = true;
-    withHwdb = false;
-    withImportd = false;
-    withIptables = false;
-    withKmod = false;
-    withLibBPF = false;
-    withLibidn2 = false;
-    withLocaled = false;
-    withLogind = false;
-    withMachined = false;
-    withNetworkd = false;
-    withNss = false;
-    withOomd = false;
-    withPam = false;
-    withPasswordQuality = false;
-    withPCRE2 = false;
-    withPolkit = false;
-    withPortabled = false;
-    withQrencode = false;
-    withRemote = false;
-    withResolved = false;
-    # withShellCompletions = true;
-    # withSysusers = true;
-    withSysupdate = false;
-    # withTimedated = true;
-    # withTimesyncd = true;
-    withTpm2Tss = false;
-    withUkify = false;
-    withUserDb = false;
-    withUtmp = false;
-    withVmspawn = false;
-    withKernelInstall = false;
-    withLibarchive = false;
-  };
+  systemd =
+    let base = prev.systemd.override {
+      withAcl = false;
+      withAnalyze = false;
+      withApparmor = false;
+      withAudit = false;
+      withBootloader = false;
+      withCompression = false;
+      withCoredump = false;
+      withCryptsetup = false;
+      withRepart = false;
+      withDocumentation = false;
+      withEfi = false;
+      withFido2 = false;
+      withHomed = false;
+      withHostnamed = false;
+      withHwdb = false;
+      withImportd = false;
+      withIptables = false;
+      withKmod = false;
+      withLibBPF = false;
+      withLibidn2 = false;
+      withLocaled = false;
+      withLogind = false;
+      withMachined = false;
+      withNetworkd = false;
+      withNss = false;
+      withOomd = false;
+      withPam = false;
+      withPasswordQuality = false;
+      withPCRE2 = false;
+      withPolkit = false;
+      withPortabled = false;
+      withQrencode = false;
+      withRemote = false;
+      withResolved = false;
+      withShellCompletions = false;
+      withSysusers = false;
+      withSysupdate = false;
+      withTimedated = false;
+      withTimesyncd = false;
+      withTpm2Tss = false;
+      withUkify = false;
+      withUserDb = false;
+      withUtmp = false;
+      withVmspawn = false;
+      withKernelInstall = false;
+      withLibarchive = false;
+    };
+    in base.overrideAttrs (o: {
+      mesonFlags = o.mesonFlags ++ [
+      #  "--optimization=s"
+        "--default-library=static"
+        "--buildtype=minsize"
+      ];
+      postInstall = o.postInstall + ''
+        rm -rf $out/share
+        rm $out/lib/libudev.so*
+        rm -rf $out/lib/systemd/catalog
+        rm -rf $out/lib/systemd/system-generators
+        rm $out/lib/systemd/systemd-backlight
+        rm $out/lib/systemd/systemd-battery-check
+        rm $out/lib/systemd/systemd-hibernate-resume
+        rm $out/lib/systemd/systemd-makefs
+        rm $out/lib/systemd/systemd-nsresourced
+        rm $out/lib/systemd/systemd-nsresourcework
+        rm $out/lib/systemd/systemd-shutdown
+        rm $out/lib/systemd/systemd-sleep
+        rm $out/lib/systemd/systemd-binfmt
+        rm $out/lib/systemd/systemd-growfs
+        rm $out/lib/systemd/systemd-mountfsd
+        rm $out/lib/systemd/systemd-mountwork
+        rm $out/lib/systemd/systemd-network-generator
+        rm $out/lib/systemd/systemd-pstore
+        rm $out/lib/systemd/systemd-remount-fs
+        rm $out/lib/systemd/systemd-reply-password
+        rm $out/lib/systemd/systemd-rfkill
+        rm $out/lib/systemd/systemd-socket-proxyd
+        rm $out/lib/systemd/systemd-ssh-proxy
+        rm $out/lib/systemd/systemd-storagetm
+        rm $out/lib/systemd/systemd-volatile-root
+        rm $out/lib/systemd/systemd-xdg-autostart-condition
+        rm -rf $out/example
+        rm $out/bin/bootctl
+        rm $out/bin/systemd-nspawn
+        rm $out/bin/systemd-ac-power
+        rm $out/bin/systemd-dissect
+        rm $out/bin/systemd-ask-password
+        rm $out/bin/systemd-cgls
+        rm $out/bin/systemd-cgtop
+        rm $out/bin/systemd-creds
+        rm $out/bin/systemd-delta
+        rm $out/bin/systemd-detect-virt
+        rm $out/bin/systemd-escape
+        rm $out/bin/systemd-id128
+        rm $out/bin/systemd-machine-id-setup
+        rm $out/bin/systemd-path
+        rm $out/bin/systemd-run
+        rm $out/bin/systemd-socket-activate
+        rm $out/bin/systemd-stdio-bridge
+        rm $out/bin/systemd-sysext
+        rm $out/bin/systemd-tty-ask-password-agent
+        rm $out/bin/systemd-vpick
+      '';
+    });
 
   ubootQemuAarch64 = final.buildUBoot {
     defconfig = "qemu_arm64_defconfig";
-- 
2.47.0


From 7705bc2a8ec528e5f06341e5143c03f9c7f89099 Mon Sep 17 00:00:00 2001
From: catvayor <catvayor@katvayor.net>
Date: Sat, 5 Oct 2024 11:50:12 +0200
Subject: [PATCH 5/8] units

---
 default.nix                 |  10 ++-
 modules/base.nix            |   8 +-
 modules/systemd/default.nix | 153 +++++++++++++++++++++++++++---------
 3 files changed, 133 insertions(+), 38 deletions(-)

diff --git a/default.nix b/default.nix
index a456110..1e064a6 100644
--- a/default.nix
+++ b/default.nix
@@ -25,7 +25,13 @@ let
 
   eval = evalModules {
     modules = [
-      {
+      ({ lib, pkgs, ... }: {
+        _module.args = {
+          utils = import "${nixpkgs}/nixos/lib/utils.nix" {
+            inherit lib pkgs;
+            config.systemd.globalEnvironment = {};
+          };
+        };
         nixpkgs = {
           source = nixpkgs;
           overlays = [ overlay ];
@@ -33,7 +39,7 @@ let
             "python-2.7.18.8"
           ];
         };
-      }
+      })
       device.module
       liminix-config
     ];
diff --git a/modules/base.nix b/modules/base.nix
index 30141a8..257200e 100644
--- a/modules/base.nix
+++ b/modules/base.nix
@@ -2,7 +2,7 @@
 ## ============
 
 
-{ lib, pkgs, config, ...}:
+{ lib, pkgs, utils, config, ...}:
 let
   inherit (lib) mkEnableOption mkOption types isDerivation hasAttr concatStringsSep mapAttrsToList;
   inherit (pkgs.pseudofile) dir symlink;
@@ -43,9 +43,15 @@ in {
         '';
       };
     };
+
+    # deprecated
     services = mkOption {
       type = types.attrsOf type_service;
     };
+
+    units = mkOption {
+      type = utils.systemdUtils.types.units;
+    };
     system.callService = mkOption {
       type = types.functionTo (types.functionTo types.anything);
     };
diff --git a/modules/systemd/default.nix b/modules/systemd/default.nix
index 7b28730..17cf0cc 100644
--- a/modules/systemd/default.nix
+++ b/modules/systemd/default.nix
@@ -1,41 +1,120 @@
-{ pkgs, ... }:
+{
+  pkgs,
+  lib,
+  config,
+  utils,
+  ...
+}:
 let
+  inherit (lib)
+    mapAttrs'
+    nameValuePair
+    mkMerge
+    mapAttrsToList
+    ;
   inherit (pkgs.pseudofile) dir symlink;
-  "getty.service" = {
-    file =
-    let
-      login = pkgs.writeScript "login" ''
-        #!/bin/ash
-        exec /bin/ash
-      '';
-    in
-    ''
-      [Unit]
-      Description="Serial shell"
+  inherit (utils.systemdUtils.lib)
+    targetToUnit
+    serviceToUnit
+    ;
+
+  units-texts = mapAttrs' (
+    _: unit:
+    nameValuePair unit.name {
+      file = unit.text;
+      mode = "0644";
+    }
+  ) config.units;
+  units-aliases = mkMerge (
+    mapAttrsToList (
+      _: unit:
+      mkMerge (
+        map (aka: {
+          ${aka} = symlink "${unit.name}";
+        }) (unit.aliases or [ ])
+      )
+    ) config.units
+  );
+  units-extraWants = mkMerge (
+    mapAttrsToList (
+      _: unit:
+      mkMerge (
+        map (unit2: {
+          "${unit2}.wants" = dir {
+            ${unit.name} = symlink "../${unit.name}";
+          };
+        }) (unit.wantedBy or [ ])
+      )
+    ) config.units
+  );
+  units-extraUpholds = mkMerge (
+    mapAttrsToList (
+      _: unit:
+      mkMerge (
+        map (unit2: {
+          "${unit2}.upholds" = dir {
+            ${unit.name} = symlink "../${unit.name}";
+          };
+        }) (unit.upheldBy or [ ])
+      )
+    ) config.units
+  );
+  units-extraRequires = mkMerge (
+    mapAttrsToList (
+      _: unit:
+      mkMerge (
+        map (unit2: {
+          "${unit2}.requires" = dir {
+            ${unit.name} = symlink "../${unit.name}";
+          };
+        }) (unit.requiredBy or [ ])
+      )
+    ) config.units
+  );
 
-      [Service]
-      ExecStart=${pkgs.util-linux}/bin/agetty --login-program ${login} ttyS0
-    '';
-    mode = "0644";
-  };
-  "default.target" = {
-    file = ''
-      [Unit]
-      Description="target to boot"
-      Wants=getty.service
-      After=getty.service
-      AllowIsolate=yes
-    '';
-  };
-  "sysinit.target" = {
-    file = ''
-      [Unit]
-      Description="sysinit.target"
-    '';
-  };
 in
 {
   config = {
+    units = {
+      default-target = targetToUnit {
+        name = "default.target";
+        aliases = [];
+        wantedBy = [];
+        requiredBy = [];
+        upheldBy = [];
+        unitConfig.Description = "target to boot";
+      };
+      sysinit-target = targetToUnit {
+        name = "sysinit.target";
+        aliases = [];
+        wantedBy = [];
+        requiredBy = [];
+        upheldBy = [];
+        unitConfig.Description = "sysinit.target";
+      };
+      agetty = serviceToUnit {
+        name = "getty.service";
+        aliases = [];
+        wantedBy = [ "default.target" ];
+        requiredBy = [];
+        upheldBy = [];
+        environment = {};
+        unitConfig = {
+          Description = "Serial Shell";
+          Before = [ "default.target" ];
+        };
+        serviceConfig.ExecStart =
+          let
+            login = pkgs.writeScript "login" ''
+              #!/bin/ash
+              . /etc/profile
+              exec /bin/ash
+            '';
+          in
+          "${pkgs.util-linux}/bin/agetty --login-program ${login} ttyS0";
+      };
+    };
+
     kernel.config = {
       CGROUPS = "y";
       DEVTMPFS = "y";
@@ -55,9 +134,13 @@ in
     filesystem = dir {
       etc = dir {
         systemd = dir {
-          system = dir {
-            inherit "default.target" "getty.service" "sysinit.target";
-          };
+          system = dir (mkMerge [
+            units-texts
+            units-aliases
+            units-extraWants
+            units-extraUpholds
+            units-extraRequires
+          ]);
         };
       };
       bin = dir {
-- 
2.47.0


From 9da241d8eca045d597f1e8e220db04cdfc68b497 Mon Sep 17 00:00:00 2001
From: catvayor <catvayor@katvayor.net>
Date: Sun, 6 Oct 2024 18:38:36 +0200
Subject: [PATCH 6/8] services & targets

---
 modules/base.nix            |  3 --
 modules/systemd/default.nix | 84 ++++++++++++++++++-------------------
 modules/systemd/types.nix   | 27 ++++++++++++
 3 files changed, 69 insertions(+), 45 deletions(-)
 create mode 100644 modules/systemd/types.nix

diff --git a/modules/base.nix b/modules/base.nix
index 257200e..1755f83 100644
--- a/modules/base.nix
+++ b/modules/base.nix
@@ -49,9 +49,6 @@ in {
       type = types.attrsOf type_service;
     };
 
-    units = mkOption {
-      type = utils.systemdUtils.types.units;
-    };
     system.callService = mkOption {
       type = types.functionTo (types.functionTo types.anything);
     };
diff --git a/modules/systemd/default.nix b/modules/systemd/default.nix
index 17cf0cc..8a9a15c 100644
--- a/modules/systemd/default.nix
+++ b/modules/systemd/default.nix
@@ -11,6 +11,7 @@ let
     nameValuePair
     mkMerge
     mapAttrsToList
+    mkOption
     ;
   inherit (pkgs.pseudofile) dir symlink;
   inherit (utils.systemdUtils.lib)
@@ -18,13 +19,15 @@ let
     serviceToUnit
     ;
 
+  systemd-types = import ./types.nix { inherit pkgs utils lib; };
+
   units-texts = mapAttrs' (
     _: unit:
     nameValuePair unit.name {
       file = unit.text;
       mode = "0644";
     }
-  ) config.units;
+  ) config.systemd.units;
   units-aliases = mkMerge (
     mapAttrsToList (
       _: unit:
@@ -33,7 +36,7 @@ let
           ${aka} = symlink "${unit.name}";
         }) (unit.aliases or [ ])
       )
-    ) config.units
+    ) config.systemd.units
   );
   units-extraWants = mkMerge (
     mapAttrsToList (
@@ -45,7 +48,7 @@ let
           };
         }) (unit.wantedBy or [ ])
       )
-    ) config.units
+    ) config.systemd.units
   );
   units-extraUpholds = mkMerge (
     mapAttrsToList (
@@ -57,7 +60,7 @@ let
           };
         }) (unit.upheldBy or [ ])
       )
-    ) config.units
+    ) config.systemd.units
   );
   units-extraRequires = mkMerge (
     mapAttrsToList (
@@ -69,49 +72,46 @@ let
           };
         }) (unit.requiredBy or [ ])
       )
-    ) config.units
+    ) config.systemd.units
   );
-
 in
 {
+  options = {
+    systemd = {
+      units = mkOption {
+        type = systemd-types.units;
+      };
+      services = mkOption {
+        type = systemd-types.services;
+      };
+      targets = mkOption {
+        type = systemd-types.targets;
+      };
+    };
+  };
   config = {
-    units = {
-      default-target = targetToUnit {
-        name = "default.target";
-        aliases = [];
-        wantedBy = [];
-        requiredBy = [];
-        upheldBy = [];
-        unitConfig.Description = "target to boot";
-      };
-      sysinit-target = targetToUnit {
-        name = "sysinit.target";
-        aliases = [];
-        wantedBy = [];
-        requiredBy = [];
-        upheldBy = [];
-        unitConfig.Description = "sysinit.target";
-      };
-      agetty = serviceToUnit {
-        name = "getty.service";
-        aliases = [];
-        wantedBy = [ "default.target" ];
-        requiredBy = [];
-        upheldBy = [];
-        environment = {};
-        unitConfig = {
-          Description = "Serial Shell";
-          Before = [ "default.target" ];
+    systemd = {
+      units = mkMerge [
+        (mapAttrs' (_: service: nameValuePair service.name (serviceToUnit service)) config.systemd.services)
+        (mapAttrs' (_: target: nameValuePair target.name (targetToUnit target)) config.systemd.targets)
+      ];
+      services = {
+        getty = {
+          wantedBy = [ "default.target" ];
+          unitConfig = {
+            Description = "Serial Shell";
+            Before = [ "default.target" ];
+          };
+          script = ''
+            #!/bin/ash
+            # . /etc/profile
+            exec /bin/ash < /dev/ttyS0 > /dev/ttyS0 2> /dev/ttyS0
+          '';
         };
-        serviceConfig.ExecStart =
-          let
-            login = pkgs.writeScript "login" ''
-              #!/bin/ash
-              . /etc/profile
-              exec /bin/ash
-            '';
-          in
-          "${pkgs.util-linux}/bin/agetty --login-program ${login} ttyS0";
+      };
+      targets = {
+        default = { };
+        sysinit = { };
       };
     };
 
diff --git a/modules/systemd/types.nix b/modules/systemd/types.nix
new file mode 100644
index 0000000..239f551
--- /dev/null
+++ b/modules/systemd/types.nix
@@ -0,0 +1,27 @@
+{
+  pkgs,
+  lib,
+  utils
+}:
+let
+  inherit (utils.systemdUtils.lib) serviceConfig unitConfig;
+  inherit (utils.systemdUtils.unitOptions) stage2ServiceOptions;
+  stage2ServiceConfig = {
+    imports = [ serviceConfig ];
+    # Default path for systemd services. Should be quite minimal.
+    config.path = lib.mkAfter [
+      pkgs.coreutils
+      # pkgs.gnugrep
+      # pkgs.gnused
+      pkgs.systemd
+    ];
+  };
+in
+{
+  inherit (utils.systemdUtils.types) units targets;
+  services = lib.types.attrsOf (lib.types.submodule [
+    unitConfig
+    stage2ServiceOptions
+    stage2ServiceConfig
+  ]);
+}
-- 
2.47.0


From 7219e6699289e8a2bf68e31f8af2406f88edd010 Mon Sep 17 00:00:00 2001
From: catvayor <catvayor@katvayor.net>
Date: Sun, 6 Oct 2024 23:27:48 +0200
Subject: [PATCH 7/8] reduce closure

---
 modules/base.nix            |  5 ++++-
 modules/busybox.nix         | 12 +++++++++---
 modules/systemd/default.nix |  3 +--
 modules/systemd/types.nix   |  6 ++++--
 overlay.nix                 | 34 ++++++++++++++++++++++++++++++++++
 5 files changed, 52 insertions(+), 8 deletions(-)

diff --git a/modules/base.nix b/modules/base.nix
index 1755f83..a12cd6e 100644
--- a/modules/base.nix
+++ b/modules/base.nix
@@ -134,7 +134,10 @@ in {
 
     # Set the useful PS1 prompt by default.
     defaultProfile.environmentVariables.PS1 = lib.mkDefault config.defaultProfile.prompt;
-    defaultProfile.packages = with pkgs; [ execline ];
+    defaultProfile.packages = with pkgs; [
+      # execline
+      systemd
+    ];
 
     boot.commandLine = [
       "panic=10 oops=panic init=/bin/init loglevel=8"
diff --git a/modules/busybox.nix b/modules/busybox.nix
index 718cafd..d22a8c3 100644
--- a/modules/busybox.nix
+++ b/modules/busybox.nix
@@ -51,7 +51,7 @@ let
 in {
   options = {
     programs.busybox = {
-      applets =  mkOption {
+      applets = mkOption {
         type = types.listOf types.str;
         description = "Applets required";
         default = [];
@@ -62,13 +62,19 @@ in {
         # other strings are also used
         description = "Other busybox config flags that do not map directly to applet names (often prefixed FEATURE_)";
         type = types.attrsOf types.nonEmptyStr;
-        default =  { };
-        example =  { FEATURE_DD_IBS_OBS = "y"; };
+        default = { };
+        example = { FEATURE_DD_IBS_OBS = "y"; };
+      };
+      package = mkOption {
+        type = types.package;
+        readOnly = true;
+        internal = true;
       };
     };
   };
   config = {
     programs.busybox = {
+      package = busybox;
       applets = minimalApplets;
       options = {
         ASH_ECHO = "y";
diff --git a/modules/systemd/default.nix b/modules/systemd/default.nix
index 8a9a15c..6dfdc3a 100644
--- a/modules/systemd/default.nix
+++ b/modules/systemd/default.nix
@@ -19,7 +19,7 @@ let
     serviceToUnit
     ;
 
-  systemd-types = import ./types.nix { inherit pkgs utils lib; };
+  systemd-types = import ./types.nix { inherit pkgs utils lib; busybox = config.programs.busybox.package; };
 
   units-texts = mapAttrs' (
     _: unit:
@@ -103,7 +103,6 @@ in
             Before = [ "default.target" ];
           };
           script = ''
-            #!/bin/ash
             # . /etc/profile
             exec /bin/ash < /dev/ttyS0 > /dev/ttyS0 2> /dev/ttyS0
           '';
diff --git a/modules/systemd/types.nix b/modules/systemd/types.nix
index 239f551..87c974e 100644
--- a/modules/systemd/types.nix
+++ b/modules/systemd/types.nix
@@ -1,7 +1,8 @@
 {
   pkgs,
   lib,
-  utils
+  utils,
+  busybox
 }:
 let
   inherit (utils.systemdUtils.lib) serviceConfig unitConfig;
@@ -10,7 +11,8 @@ let
     imports = [ serviceConfig ];
     # Default path for systemd services. Should be quite minimal.
     config.path = lib.mkAfter [
-      pkgs.coreutils
+      busybox
+      # pkgs.coreutils
       # pkgs.gnugrep
       # pkgs.gnused
       pkgs.systemd
diff --git a/overlay.nix b/overlay.nix
index 1e9b150..c79866c 100644
--- a/overlay.nix
+++ b/overlay.nix
@@ -335,8 +335,28 @@ extraPkgs // {
       };
     }) { };
 
+  writeShellScriptBin = name: text:
+    final.writeTextFile {
+      inherit name;
+      executable = true;
+      destination = "/bin/${name}";
+      text = ''
+        #!/bin/ash
+        ${text}
+      '';
+      checkPhase = ''
+        ${final.stdenv.shellDryRun} "$target"
+      '';
+      meta.mainProgram = name;
+    };
+
   systemd =
     let base = prev.systemd.override {
+      kbd = "";
+      coreutils = "";
+      bash = null;
+      bashInteractive = "";
+
       withAcl = false;
       withAnalyze = false;
       withApparmor = false;
@@ -389,6 +409,17 @@ extraPkgs // {
       #  "--optimization=s"
         "--default-library=static"
         "--buildtype=minsize"
+        # (final.lib.mesonBool "static-libsystemd" true)
+        # (final.lib.mesonBool "standalone-binaries" true)
+
+      #  (final.lib.mesonBool "link-udev-shared" false)
+      #  (final.lib.mesonBool "link-executor-shared" false)
+      #  (final.lib.mesonBool "link-systemctl-shared" false)
+      #  (final.lib.mesonBool "link-networkd-shared" false)
+      #  (final.lib.mesonBool "link-timesyncd-shared" false)
+      #  (final.lib.mesonBool "link-journalctl-shared" false)
+      #  (final.lib.mesonBool "link-boot-shared" false)
+      #  (final.lib.mesonBool "link-portabled-shared" false)
       ];
       postInstall = o.postInstall + ''
         rm -rf $out/share
@@ -438,6 +469,9 @@ extraPkgs // {
         rm $out/bin/systemd-sysext
         rm $out/bin/systemd-tty-ask-password-agent
         rm $out/bin/systemd-vpick
+
+        # rm $out/lib/libsystemd.a
+        # rm $out/lib/systemd/libsystemd-shared-256.so
       '';
     });
 
-- 
2.47.0


From 643264bd69660dd01df51d72e00be56cb9fef13d Mon Sep 17 00:00:00 2001
From: catvayor <catvayor@katvayor.net>
Date: Fri, 8 Nov 2024 22:39:23 +0100
Subject: [PATCH 8/8] fix(update): enableScrictShellChecks

---
 modules/systemd/types.nix | 1 +
 1 file changed, 1 insertion(+)

diff --git a/modules/systemd/types.nix b/modules/systemd/types.nix
index 87c974e..30ca1fe 100644
--- a/modules/systemd/types.nix
+++ b/modules/systemd/types.nix
@@ -22,6 +22,7 @@ in
 {
   inherit (utils.systemdUtils.types) units targets;
   services = lib.types.attrsOf (lib.types.submodule [
+    { enableStrictShellChecks = false; }
     unitConfig
     stage2ServiceOptions
     stage2ServiceConfig
-- 
2.47.0