WordPress at a glance
action is not described

pre_auto_update action-hook . WP 4.4.0

Fires immediately prior to an auto-update.

Usage

add_action( 'pre_auto_update', 'action_function_name_4965', 10, 3 );
function action_function_name_4965( $type, $item, $context ){
	// action...
}
$type(string)
The type of update being checked: 'core', 'theme', 'plugin', or 'translation'.
$item(object)
The update offer.
$context(string)
The filesystem context (a path) against which filesystem access and status should be checked.

Where the hook is called

WP_Automatic_Updater::update()
wp-admin/includes/class-wp-automatic-updater.php 291
do_action( 'pre_auto_update', $type, $item, $context );

Where the hook is used (in WP core)

Does not used.