Metadata Refresh Tool aka Site Refresh
Shibboleth provides a simple tool called siterefresh in the /opt/shibboleth/bin folder of the distribution to maintain metadata files referenced by shibboleth.xml. You can find out more about siterefresh at the Internet2 Shibboleth site
Example
The example code below updates the testincommon.xml metadata from the InCommon site.
sudo /usr/sbin/siterefresh --out /etc/shibboleth/testincommon.xml --cert /etc/shibboleth/incommon.pem --url http://wayf.incommonfederation.org/InCommon/InCommon-metadata.xml