WordPress at a glance
action is not described

rss2_ns action-hook . WP 2.0.0

Fires at the end of the RSS root to add namespaces.

Usage

add_action( 'rss2_ns', 'action_function_name_4228' );
function action_function_name_4228(){
	// action...
}

Where the hook is called

In file: /wp-includes/feed-rss2.php
rss2_ns
wp-includes/feed-rss2.php 36
do_action( 'rss2_ns' );
wp-includes/feed-rss2-comments.php 22
do_action( 'rss2_ns' );

Where the hook is used (in WP core)

Does not used.