magento-set-defaults-address.php

<?php

require_once ("app/Mage.php");
umask(0);
Mage::app("default");


$collection = Mage::getModel('customer/customer')->getCollection()->addAttributeToSelect('*');

foreach ($collection as $customer) {
	
	$customerObj = Mage::getModel('customer/customer')->load( $customer->getId() );
	
	if ( ! $customerObj->getDefaultBillingAddress() ) {
		foreach ($customerObj->getAddresses() as $address) {
			$address->setIsDefaultBilling(true);
			continue; // we only want to set first address of the customer as default billing address
		}
	}

	if ( ! $customerObj->getDefaultShippingAddress() ) {
		foreach ($customerObj->getAddresses() as $address) {
			$address->setIsDefaultShipping(true);
			continue; // we only want to set first address of the customer as default shipping address
		}
	}
}