This FAQ will show you how to auto update the Google Sitemap in your Magento website in two easy steps:

1. Create a CRON job in your hosting admin like the screenshot below. This will ensure that any scheduled updates will be triggered.

   

   This is the command you need to use (replace the pathname, which is the blue text part, with your own pathname)

   php /home/acname/public_html/cron.php > /dev/null

2. Now go to System>Configuration in your Magento admin and enable the Google Sitemap update as follows