Add a note regarding rsync and ssh-agent/passphrase-less keys

docsite/rst/playbooks2.rst

@@ -912,6 +912,9 @@ Here is an example::
       - name: recursively copy files from management server to target
         local_action: command rsync -a /path/to/files $inventory_hostname:/path/to/target/
 
+Note that you must have passphrase-less SSH keys or an ssh-agent configured for this to work, otherwise rsync
+will need to ask for a passphrase.
+
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