I originally posted this article over at Failverse, but I figured I should have it on my own blog as well. This guide may be a little dated as Rackspace has updated their host servers to utilize a newer version of Xen. Your mileage may vary.
This guide will walk you through installing a custom linux distro to Rackspace Cloud Servers without the need of taring up a file system from a donor box. This particular guide is specific to openSuse, but the same method can be used to install other distros that support automated/remote install.
This process is entirely unsupported by Rackspace.
First, some documentation before we get started:
http://en.opensuse.org/SDB:Remote_installation
http://en.opensuse.org/SDB:Linuxrc