ESRI's Geoportal wants an LDAP server, and suggests using Apache Directory Server.

I started a new VM using the image usgin2-atpms. Installation was as easy as:

wget http://apache.imghat.com//directory/apacheds/unstable/1.5/1.5.7/apacheds-1.5.7-i386.deb
sudo dpkg -i /home/ubuntu/apacheds-1.5.7-i386.deb

It was easy to connect to via SSH Tunnel to port 10389. The next step would be to fix some issues with the instance and its data-store, remove the extra MySQL installation, and then move on to configuration of the PostgreSQL database.