The documentation (
https://apereo.github.io/cas/development/installation/Configuration-Properties.html#saml-idp) says that the
cas.authn.samlIdp.metadata.location
property should be set to a URI/URL like "file:/etc/cas/saml". However, if you do this, the server will die on startup with "Metadata directory location file:/etc/cas/saml cannot be located/created". (You will get the same error if you use "file:///etc/cas/saml".)
If you leave the property unset, everything works correctly. Likewise, if you set the property to "/etc/cas/saml" (instead of "file:/etc/cas/saml"), everything works correctly.
This is easily worked around, but probably ought to be corrected at some point.
--Dave