1 files changed, 61 insertions, 0 deletions
diff --git a/nixpkgs/nixos/modules/virtualisation/amazon-init.nix b/nixpkgs/nixos/modules/virtualisation/amazon-init.nix
new file mode 100644
index 00000000000..8032b2c6d7c
--- /dev/null
+++ b/nixpkgs/nixos/modules/virtualisation/amazon-init.nix
@@ -0,0 +1,61 @@
+{ config, pkgs, ... }:
+
+let
+  script = ''
+    #!${pkgs.runtimeShell} -eu
+
+    echo "attempting to fetch configuration from EC2 user data..."
+
+    export HOME=/root
+    export PATH=${pkgs.lib.makeBinPath [ config.nix.package pkgs.systemd pkgs.gnugrep pkgs.gnused config.system.build.nixos-rebuild]}:$PATH
+    export NIX_PATH=/nix/var/nix/profiles/per-user/root/channels/nixos:nixos-config=/etc/nixos/configuration.nix:/nix/var/nix/profiles/per-user/root/channels
+
+    userData=/etc/ec2-metadata/user-data
+
+    if [ -s "$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 sed '/^\(#\|SSH_HOST_.*\)/d' < "$userData" | grep -q '\S'; then
+        channels="$(grep '^###' "$userData" | sed 's|###\s*||')"
+        printf "%s" "$channels" | while read channel; do
+          echo "writing channel: $channel"
+        done
+
+        if [[ -n "$channels" ]]; then
+          printf "%s" "$channels" > /root/.nix-channels
+          nix-channel --update
+        fi
+
+        echo "setting configuration from EC2 user data"
+        cp "$userData" /etc/nixos/configuration.nix
+      else
+        echo "user data does not appear to be a Nix expression; ignoring"
+        exit
+      fi
+    else
+      echo "no user data is available"
+      exit
+    fi
+
+    nixos-rebuild switch
+  '';
+in {
+  systemd.services.amazon-init = {
+    inherit script;
+    description = "Reconfigure the system from EC2 userdata on startup";
+
+    wantedBy = [ "multi-user.target" ];
+    after = [ "multi-user.target" ];
+    requires = [ "network-online.target" ];
+ 
+    restartIfChanged = false;
+    unitConfig.X-StopOnRemoval = false;
+
+    serviceConfig = {
+      Type = "oneshot";
+      RemainAfterExit = true;
+    };
+  };
+}
+