Avoid to require non crossplatform packages

Change-Id: Icd8595d095a6ebd099235be158dcd16d92eb94b1
diff --git a/linux/system/single/debian.yml b/linux/system/single/debian.yml
new file mode 100644
index 0000000..b6d0b2b
--- /dev/null
+++ b/linux/system/single/debian.yml
@@ -0,0 +1,10 @@
+classes:
+- system.linux.system.single
+
+# DEBIAN family overrides
+parameters:
+  linux:
+    system:
+      package:
+        python-msgpack:
+          version: latest
diff --git a/linux/system/single.yml b/linux/system/single/init.yml
similarity index 96%
rename from linux/system/single.yml
rename to linux/system/single/init.yml
index ccde6ad..1e68380 100644
--- a/linux/system/single.yml
+++ b/linux/system/single/init.yml
@@ -15,8 +15,6 @@
           name: root
           home: /root
       package:
-        python-msgpack:
-          version: latest
         cloud-init:
           version: purged
         unattended-updates:
diff --git a/linux/system/single/rhel.yml b/linux/system/single/rhel.yml
new file mode 100644
index 0000000..38dba03
--- /dev/null
+++ b/linux/system/single/rhel.yml
@@ -0,0 +1,4 @@
+classes:
+- system.linux.system.single
+
+# RHEL family overrides