Support defaults in linux.system.config
diff --git a/linux/system/config.sls b/linux/system/config.sls
index 98bb767..3b155e7 100644
--- a/linux/system/config.sls
+++ b/linux/system/config.sls
@@ -21,6 +21,9 @@
     - defaults:
         pillar: {{ config.pillar|yaml }}
         grains: {{ config.get('grains', {}) }}
+        {%- for key, value in service_config.get('defaults', {}) %}
+        {{ key }}: {{ value }}
+        {%- endfor %}
 
           {%- endfor %}
         {%- endif %}