[DOCS] Disable Metricbeat system module (#42601)

docs/reference/monitoring/configuring-metricbeat.asciidoc

@@ -144,6 +144,23 @@ file.
 // end::remote-monitoring-user[]
 --
 
+. Optional: Disable the system module in {metricbeat}.
++
+--
+// tag::disable-system-module[]
+By default, the {metricbeat-ref}/metricbeat-module-system.html[system module] is
+enabled. The information it collects, however, is not shown on the *Monitoring*
+page in {kib}. Unless you want to use that information for other purposes, run
+the following command:
+
+["source","sh",subs="attributes,callouts"]
+----------------------------------------------------------------------
+metricbeat modules disable system
+----------------------------------------------------------------------
+
+// end::disable-system-module[] 
+--
+
 . Identify where to send the monitoring data. +
 +
 --