It turns out that our customer is using Fedora Directory Server. Installing an Ubuntu server was probably not the best option then...
No matter. It is certainly possible to install FDS on Ubuntu: the full instructions are here. Mercifully, however, someone who should be given a medal has created the install packages. These can be downloaded here. It is just a case of adding
deb http://ubuntu.opencodes.org gutsy main
to the /etc/apt/soures.list file, running apt-get update, and then running
apt-get install fedora-ds-admin
I also ran apt-get install fedora-idm-console. I don't know if this is really necessary. Ubuntu server doesn't have a desktop, but I do want to use the Windows Fedora IDM Console remotely. That done, I ran
It failed. The error was a result of a "Netscape Portable Runtime error - 5977: libicui18n.so.36: cannot open shared object file: No such file or directory" The solution to this was to install libicu36:
apt-get install libicu36
why this library wasn't already installed, I don't know - unless it is installed with the desktop. I also installed termcap (mistakenly) thinking this had something to do with it. The Ubuntu instructions say that Termcap should be installed. However, installing Termcap on 64-bit Ubuntu turns out to be a pain. It requires downloading the 64-bit rpm from Fedora, running alien to convert it to a .deb file, and then installing the file using dpkg. There are good instructions here.
Once libicu36 was installed, I ran setup-ds-admin.pl again and it worked perfectly! I just accepted the defaults - happily noting all the correct domain name settings :-) - and the job was done.