Sentinel example config: explain you don't need to specify slaves.

sentinel.conf

@@ -20,6 +20,12 @@ dir /tmp
 # be elected by the majority of the known Sentinels in order to
 # start a failover, so no failover can be performed in minority.
 #
+# Slaves are auto-discovered, so you don't need to specify slaves in
+# any way. Sentinel itself will rewrite this configuration file adding
+# the slaves using additional configuration options.
+# Also note that the configuration file is rewritten when a
+# slave is promoted to master.
+#
 # Note: master name should not include special characters or spaces.
 # The valid charset is A-z 0-9 and the three characters ".-_".
 sentinel monitor mymaster 127.0.0.1 6379 2