begin minimization of systemd

trivial part

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"

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"

modules/s6/scripts/rc.shutdown

@@ -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

modules/s6/scripts/rc.shutdown.final

@@ -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

modules/s6/scripts/runlevel

@@ -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"

modules/systemd/default.nix

@@ -0,0 +1,68 @@
+{ 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 ${login} ttyS0
+    '';
+    mode = "0644";
+  };
+  "default.target" = {
+    file = ''
+      [Unit]
+      Description="target to boot"
+      Wants=getty.service
+      After=getty.service
+      AllowIsolate=yes
+    '';
+  };
+  "sysinit.target" = {
+    file = ''
+      [Unit]
+      Description="sysinit.target"
+    '';
+  };
+in
+{
+  config = {
+    kernel.config = {
+      CGROUPS = "y";
+      DEVTMPFS = "y";
+      INOTIFY_USER = "y";
+      SIGNALFD = "y";
+      TIMERFD = "y";
+      EPOLL = "y";
+      UNIX = "y";
+      SYSFS = "y";
+      PROC_FS = "y";
+      FHANDLE = "y";
+    };
+    boot.commandLine = [
+      "systemd.log_level=7"
+      #"systemd.crash_shell=true"
+    ];
+    filesystem = dir {
+      etc = dir {
+        systemd = dir {
+          system = dir {
+            inherit "default.target" "getty.service" "sysinit.target";
+          };
+        };
+      };
+      bin = dir {
+        init = symlink "${pkgs.systemd}/bin/init";
+      };
+    };
+  };
+}

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: {
@@ -330,13 +335,14 @@ extraPkgs // {
       };
     }) { };
 
-  systemd = prev.systemd.override {
+  systemd =
+    let base = prev.systemd.override {
       withAcl = false;
       withAnalyze = false;
       withApparmor = false;
       withAudit = false;
       withBootloader = false;
-    # withCompression = true;
+      withCompression = false;
       withCoredump = false;
       withCryptsetup = false;
       withRepart = false;
@@ -344,7 +350,7 @@ extraPkgs // {
       withEfi = false;
       withFido2 = false;
       withHomed = false;
-    # withHostnamed = true;
+      withHostnamed = false;
       withHwdb = false;
       withImportd = false;
       withIptables = false;
@@ -352,24 +358,24 @@ 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;
-    # withShellCompletions = true;
-    # withSysusers = true;
+      withResolved = false;
+      withShellCompletions = false;
+      withSysusers = false;
       withSysupdate = false;
-    # withTimedated = true;
-    # withTimesyncd = true;
+      withTimedated = false;
+      withTimesyncd = false;
       withTpm2Tss = false;
       withUkify = false;
       withUserDb = false;
@@ -378,6 +384,62 @@ extraPkgs // {
       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";