Trivial example of enabling mod_auth_cas on Apache on recent-ish Ubuntu

enable-mod-auth-cas.sh

sudo apt-get install libapache2-mod-auth-cas
sudo a2enmod auth_cas
# Install site config updates above
sudo service apache2 restart

site-config.apacheconf

<VirtualHost …>

    CASCookiePath /var/cache/apache2/mod_auth_cas/
    CASLoginURL https://CAS_AUTH_URL/auth
    CASValidateURL https://CAS_AUTH_URL/serviceValidate

    # If you use a wild-card SSL certificate, perhaps on your testing infrastructure:
    CASAllowWildcardCert on

    <Location /admin/>
        AuthType CAS
        require valid-user
    </Location>
</VirtualHost>