Update cacti conf example to give more details about the field names …

…parameter

conf.d/cacti.yaml.example

@@ -9,6 +9,25 @@ instances:
     # The `rrd_path` will probably be '/var/lib/cacti/rra' on Ubuntu
     # or '/var/www/html/cacti/rra' on any other machines.
     #
+    # The `field_names` is an optional parameter to specify which field_names 
+    # should be used to determine if a device is a real device. You can let it 
+    # commented out as the default values should satisfy your needs.
+    # You can run the following query to determine your field names:
+    #       SELECT
+    #            h.hostname as hostname,
+    #            hsc.field_value as device_name,
+    #            dt.data_source_path as rrd_path,
+    #            hsc.field_name as field_name
+    #        FROM data_local dl
+    #            JOIN host h on dl.host_id = h.id
+    #            JOIN data_template_data dt on dt.local_data_id = dl.id
+    #            LEFT JOIN host_snmp_cache hsc on h.id = hsc.host_id
+    #                AND dl.snmp_index = hsc.snmp_index
+    #        WHERE dt.data_source_path IS NOT NULL
+    #        AND dt.data_source_path != ''
+    #
+    #
+    #
     # The `rrd_whitelist` is a path to a text file that has a list of patterns,
     # one per line, that should be fetched. If no whitelist is specified, all
     # metrics will be fetched.
@@ -17,8 +36,8 @@ instances:
         mysql_user: MYSQL_USER
         mysql_password: MYSQL_PASSWORD
         rrd_path: /path/to/cacti/rra
-        field_names:
-            - ifName
-            - dskDevice
-            - ifIndex       
+        #field_names:
+        #    - ifName
+        #    - dskDevice
+        #    - ifIndex       
         #rrd_whitelist: /path/to/rrd_whitelist.txt