machineid: add configuration option for machine-id

SEE #2225

src/modules/machineid/machineid.conf

@@ -13,6 +13,11 @@
 # Whether to create /etc/machine-id for systemd.
 # The default is *false*.
 systemd: true
+# If systemd is true, the kind of /etc/machine-id to create in the target
+#  - uuid (default) generates a UUID
+#  - blank creates the file but leaves it empty at 0 bytes
+#  - literal-uninitialized creates the file and writes the string "uninitialized\n"
+systemd-style: uuid
 
 # Whether to create /var/lib/dbus/machine-id for D-Bus.
 # The default is *false*.

src/modules/machineid/machineid.schema.yaml

@@ -7,6 +7,7 @@ additionalProperties: false
 type: object
 properties:
     systemd: { type: boolean, default: false }
+    "systemd-style": { type: string, enum: [ uuid, blank, literal-uninitialized ] }
     dbus: { type: boolean, default: false }
     "dbus-symlink": { type: boolean, default: false }
     "entropy-copy": { type: boolean, default: false }