Once I'd got the underlying UML host system installed, I set about creating a couple of UML instances, one for the 2006 linux.conf.au guys, and one for mucking around in, and will be for the 2007 guys when they want to get the ball rolling.
Next I ran into some bizarre problems with UML. The host is running a 2.6.8 kernel with the SKAS patch, and the UMLs themselves are running 2.6.10. I used rootstrap to create the initial filesystem, and then jumped on the console to install OpenSSH, and then SSH in to do the rest of the configuration.
The problem was I got struck by #298427, which is indeed a bizarre little bug. I initially worked around this by reconfiguring the SSH daemon not to use PAM and setting PasswordAuthentication to yes. I later hit some strange segmentation faults with BIND 9 as well, so I tried the alternative workaround I had subsequently found, which was to move /lib/tls out of the way.
Given that this seems to fix the problem, and it's bigger than just SSH, I'm guessing the problem is actually some sort of libc6 + UML + 2.6.10 problem or something, although I haven't had this problem previously, and I was using the exact same UML kernel and host kernel, so it's a bit odd. Maybe its a Celeron thing or something. I don't know what the implications are of having /lib/tls nonexistent at the moment either, but it can't be ideal.