add autoupdater

modules/nix/autoupdater.nix

@@ -0,0 +1,85 @@
+{
+  config,
+  pkgs,
+  lib,
+  ...
+}:
+with lib; {
+  options.nix.auto-update = {
+    enable = mkEnableOption "enable automatic updates";
+    reboot = mkEnableOption "Reboot if kernel change";
+    hydraServer = mkOption {
+      type = types.str;
+      description = "Location of hydra server";
+      default = "https://hydra.chir.rs";
+    };
+    source = mkOption {
+      type = types.str;
+      description = "Source to update from";
+      default = "${config.nix.auto-update.hydraServer}/jobset/nixos-config/pr618/evals";
+    };
+    attr = mkOption {
+      type = types.str;
+      description = "Attribute to update from";
+      default = "nixosConfigurations.${config.networking.hostName}";
+    };
+  };
+
+  config.nix.auto-update.enable = mkDefault true;
+  config.nix.auto-update.reboot = mkDefault true;
+  systemd.services.nixos-upgrade = {
+    description = "NixOS Upgrade";
+    restartIfChanged = false;
+    unitConfig.X-StopOnRemoval = false;
+
+    wants = ["network-online.target"];
+    after = ["network-online.target"];
+
+    serviceConfig.Type = "oneshot";
+
+    script = ''
+      #!${pkgs.bash}/bin/bash
+      set -euxo pipefail
+      builds=$(${pkgs.curl}/bin/curl -H "accept: application/json" ${config.options.nix.auto-update.source} | ${pkgs.jq}/bin/jq -r '.evals[0].builds[]')
+      for build in $builds; do
+        doc=$(${pkgs.curl}/bin/curl -H "accept: application/json" ${config.options.nix.auto-update-hydraServer}/build/$build)
+        jobname=$(echo $doc | ${pkgs.jq}/bin/jq -r '.job')
+        if [ "$jobname" = "${config.options.nix.auto-update.attr} ]; then
+          drvname=$(echo $doc | ${pkgs.jq}/bin/jq -r '.drvpath')
+          output=$(${pkgs.nix}/bin/nix-store -r $drvname)
+          ${pkgs.nix}/bin/nix-env -p /nix/var/nix/profiles/system --set $output
+          ${
+        if config.nix.auto-update.reboot
+        then ''
+          $output/bin/switch-to-configuration boot
+          booted="$(${pkgs.coreutils}/bin/readlink /run/booted-system/{initrd,kernel,kernel-modules})"
+          built="$(${pkgs.coreutils}/bin/readlink $output/{initrd,kernel,kernel-modules})"
+          if [ "$booted" = "$built" ]; then
+            $output/bin/switch-to-configuration switch
+          else
+              ${pkgs.systemd}/bin/shutdown -r +1
+          fi
+          exit
+        ''
+        else ''
+          $output/bin/switch-to-configuration switch
+        ''
+      }
+        fi
+      done
+    '';
+  };
+
+  systemd.timers.nixos-upgrade = {
+    enable = config.nix.auto-update.enable;
+    description = "Automatically update nixos";
+    requires = ["nixos-upgrade.service"];
+    wants = ["network-online.target"];
+    after = ["network-online.target"];
+    wantedBy = ["multi-user.target"];
+    timerConfig = {
+      OnUnitActiveSec = "30min";
+      RandomizedDelaySec = "1h";
+    };
+  };
+}

modules/nix/default.nix

@@ -2,6 +2,7 @@
   imports = [
     ./link-inputs.nix
     ./lix.nix
+    ./autoupdater.nix
   ];
   nix.settings = {
     substituters = [