1 files changed, 95 insertions, 0 deletions
diff --git a/nixos/modules/virtualisation/digital-ocean-init.nix b/nixos/modules/virtualisation/digital-ocean-init.nix
new file mode 100644
index 00000000000..4339d91de16
--- /dev/null
+++ b/nixos/modules/virtualisation/digital-ocean-init.nix
@@ -0,0 +1,95 @@
+{ config, pkgs, lib, ... }:
+with lib;
+let
+  cfg = config.virtualisation.digitalOcean;
+  defaultConfigFile = pkgs.writeText "digitalocean-configuration.nix" ''
+    { modulesPath, lib, ... }:
+    {
+      imports = lib.optional (builtins.pathExists ./do-userdata.nix) ./do-userdata.nix ++ [
+        (modulesPath + "/virtualisation/digital-ocean-config.nix")
+      ];
+    }
+  '';
+in {
+  options.virtualisation.digitalOcean.rebuildFromUserData = mkOption {
+    type = types.bool;
+    default = true;
+    example = true;
+    description = "Whether to reconfigure the system from Digital Ocean user data";
+  };
+  options.virtualisation.digitalOcean.defaultConfigFile = mkOption {
+    type = types.path;
+    default = defaultConfigFile;
+    defaultText = literalDocBook ''
+      The default configuration imports user-data if applicable and
+      <literal>(modulesPath + "/virtualisation/digital-ocean-config.nix")</literal>.
+    '';
+    description = ''
+      A path to a configuration file which will be placed at
+      <literal>/etc/nixos/configuration.nix</literal> and be used when switching to
+      a new configuration.
+    '';
+  };
+
+  config = {
+    systemd.services.digitalocean-init = mkIf cfg.rebuildFromUserData {
+      description = "Reconfigure the system from Digital Ocean userdata on startup";
+      wantedBy = [ "network-online.target" ];
+      unitConfig = {
+        ConditionPathExists = "!/etc/nixos/do-userdata.nix";
+        After = [ "digitalocean-metadata.service" "network-online.target" ];
+        Requires = [ "digitalocean-metadata.service" ];
+        X-StopOnRemoval = false;
+      };
+      serviceConfig = {
+        Type = "oneshot";
+        RemainAfterExit = true;
+      };
+      restartIfChanged = false;
+      path = [ pkgs.jq pkgs.gnused pkgs.gnugrep pkgs.systemd config.nix.package config.system.build.nixos-rebuild ];
+      environment = {
+        HOME = "/root";
+        NIX_PATH = concatStringsSep ":" [
+          "/nix/var/nix/profiles/per-user/root/channels/nixos"
+          "nixos-config=/etc/nixos/configuration.nix"
+          "/nix/var/nix/profiles/per-user/root/channels"
+        ];
+      };
+      script = ''
+        set -e
+        echo "attempting to fetch configuration from Digital Ocean user data..."
+        userData=$(mktemp)
+        if jq -er '.user_data' /run/do-metadata/v1.json > $userData; then
+          # If the user-data looks like it could be a nix expression,
+          # copy it over. Also, look for a magic three-hash comment and set
+          # that as the channel.
+          if nix-instantiate --parse $userData > /dev/null; then
+            channels="$(grep '^###' "$userData" | sed 's|###\s*||')"
+            printf "%s" "$channels" | while read channel; do
+              echo "writing channel: $channel"
+            done
+
+            if [[ -n "$channels" ]]; then
+              printf "%s" "$channels" > /root/.nix-channels
+              nix-channel --update
+            fi
+
+            echo "setting configuration from Digital Ocean user data"
+            cp "$userData" /etc/nixos/do-userdata.nix
+            if [[ ! -e /etc/nixos/configuration.nix ]]; then
+              install -m0644 ${cfg.defaultConfigFile} /etc/nixos/configuration.nix
+            fi
+          else
+            echo "user data does not appear to be a Nix expression; ignoring"
+            exit
+          fi
+
+          nixos-rebuild switch
+        else
+          echo "no user data is available"
+        fi
+        '';
+    };
+  };
+  meta.maintainers = with maintainers; [ arianvp eamsden ];
+}