A simple Docker container that uses the keygen.sh and metadata.sh scripts directly from the Shibboleth SP distribution. It then puts the keys and metadata file in /working.
docker run -v $(pwd)/test:/working -e CERT_YEARS=1 -e FQDN=test.domain.tld jhulibraries/saml-sp-metadata-gen:latest
CERT_YEARS (optional): The number of years before certificate expires. Default is 10. FQDN: The fully qualified domain name for the idP to redirect back to. Not a url.
This follows the standard format that the JHU Libraries use, published here: https://wiki.library.jhu.edu/display/SYST/Deploying+Shib+auth+on+a+library+server