Example sentinel conf: document requirepass.

sentinel.conf

@@ -112,6 +112,14 @@ sentinel monitor mymaster 127.0.0.1 6379 2
 # Default is 30 seconds.
 sentinel down-after-milliseconds mymaster 30000
 
+# requirepass <password>
+#
+# You can configure Sentinel itself to require a password, however when doing
+# so Sentinel will try to authenticate with the same password to all the
+# other Sentinels. So you need to configure all your Sentinels in a given
+# group with the same "requirepass" password. Check the following documentation
+# for more info: https://redis.io/topics/sentinel
+
 # sentinel parallel-syncs <master-name> <numreplicas>
 #
 # How many replicas we can reconfigure to point to the new replica simultaneously