System requirements

The XML sitemap module's requirements are no different than a standard PHP installation.

Web server

1. Your Drupal install should not contain a sitemap.xml file in the Drupal root directory as this will prevent the module from working.
2. For larger sites, your server must be able to handle large write operations to your site's files and temporary directories during cron.
3. You must have cron configured properly in order for the sitemaps to be generated.

PHP

1. PHP XML extension. This extension is enabled by default in a standard PHP installation, except for some CentOS systems. This extension is required to run Drupal 7.
2. PHP XML Writer extension. This extension is enabled by default in a standard PHP installation, except on some Gentoo systems.