nixos: Add ec2-metadata-fetcher.nix file

To share the metadata fetcher script between ec2 and Openstack images.

nixos/modules/virtualisation/amazon-image.nix

@@ -8,7 +8,13 @@
 
 with lib;
 
-let cfg = config.ec2; in
+let
+  cfg = config.ec2;
+  metadataFetcher = import ./ec2-metadata-fetcher.nix {
+    targetRoot = "$targetRoot/";
+    wgetExtraOptions = "-q";
+  };
+in
 
 {
   imports = [ ../profiles/headless.nix ./ec2-data.nix ./amazon-init.nix ];
@@ -61,26 +67,7 @@ let cfg = config.ec2; in
     # Nix operations.
     boot.initrd.postMountCommands =
       ''
-        metaDir=$targetRoot/etc/ec2-metadata
-        mkdir -m 0755 -p "$metaDir"
-
-        echo "getting EC2 instance metadata..."
-
-        if ! [ -e "$metaDir/ami-manifest-path" ]; then
-          wget -q -O "$metaDir/ami-manifest-path" http://169.254.169.254/1.0/meta-data/ami-manifest-path
-        fi
-
-        if ! [ -e "$metaDir/user-data" ]; then
-          wget -q -O "$metaDir/user-data" http://169.254.169.254/1.0/user-data && chmod 600 "$metaDir/user-data"
-        fi
-
-        if ! [ -e "$metaDir/hostname" ]; then
-          wget -q -O "$metaDir/hostname" http://169.254.169.254/1.0/meta-data/hostname
-        fi
-
-        if ! [ -e "$metaDir/public-keys-0-openssh-key" ]; then
-          wget -q -O "$metaDir/public-keys-0-openssh-key" http://169.254.169.254/1.0/meta-data/public-keys/0/openssh-key
-        fi
+        ${metadataFetcher}
 
         diskNr=0
         diskForUnionfs=

nixos/modules/virtualisation/ec2-metadata-fetcher.nix

@@ -0,0 +1,23 @@
+{ targetRoot, wgetExtraOptions }:
+''
+  metaDir=${targetRoot}etc/ec2-metadata
+  mkdir -m 0755 -p "$metaDir"
+
+  echo "getting EC2 instance metadata..."
+
+  if ! [ -e "$metaDir/ami-manifest-path" ]; then
+    wget ${wgetExtraOptions} -O "$metaDir/ami-manifest-path" http://169.254.169.254/1.0/meta-data/ami-manifest-path
+  fi
+
+  if ! [ -e "$metaDir/user-data" ]; then
+    wget ${wgetExtraOptions} -O "$metaDir/user-data" http://169.254.169.254/1.0/user-data && chmod 600 "$metaDir/user-data"
+  fi
+
+  if ! [ -e "$metaDir/hostname" ]; then
+    wget ${wgetExtraOptions} -O "$metaDir/hostname" http://169.254.169.254/1.0/meta-data/hostname
+  fi
+
+  if ! [ -e "$metaDir/public-keys-0-openssh-key" ]; then
+    wget ${wgetExtraOptions} -O "$metaDir/public-keys-0-openssh-key" http://169.254.169.254/1.0/meta-data/public-keys/0/openssh-key
+  fi
+''

nixos/modules/virtualisation/openstack-config.nix

@@ -2,6 +2,12 @@
 
 with lib;
 
+let
+  metadataFetcher = import ./ec2-metadata-fetcher.nix {
+    targetRoot = "/";
+    wgetExtraOptions = "--retry-connrefused";
+  };
+in
 {
   imports = [
     ../profiles/qemu-guest.nix
@@ -39,28 +45,7 @@ with lib;
       before = [ "apply-ec2-data.service" "amazon-init.service"];
       wants = [ "network-online.target" ];
       after = [ "network-online.target" ];
-      script =
-        ''
-          metaDir=/etc/ec2-metadata
-          mkdir -m 0755 -p "$metaDir"
-
-          echo "getting Openstack instance metadata (via EC2 API)..."
-          if ! [ -e "$metaDir/ami-manifest-path" ]; then
-            wget --retry-connrefused -O "$metaDir/ami-manifest-path" http://169.254.169.254/1.0/meta-data/ami-manifest-path
-          fi
-
-          if ! [ -e "$metaDir/user-data" ]; then
-            wget --retry-connrefused -O "$metaDir/user-data" http://169.254.169.254/1.0/user-data && chmod 600 "$metaDir/user-data"
-          fi
-
-          if ! [ -e "$metaDir/hostname" ]; then
-            wget --retry-connrefused -O "$metaDir/hostname" http://169.254.169.254/1.0/meta-data/hostname
-          fi
-
-          if ! [ -e "$metaDir/public-keys-0-openssh-key" ]; then
-            wget --retry-connrefused -O "$metaDir/public-keys-0-openssh-key" http://169.254.169.254/1.0/meta-data/public-keys/0/openssh-key
-          fi
-        '';
+      script = metadataFetcher;
       restartIfChanged = false;
       unitConfig.X-StopOnRemoval = false;
       serviceConfig = {