Support installing OpenIndiana from LiveUSB into an existing rpool
I decided to upgrade my test OpenSolaris system (doubling as a home NAS) and the only option I have to update it from LiveUSB is to destroy the old partition table and ZFS rpool, and restart from scratch.
The option to update via IPS over the network was not explored because the Internet here is flaky and pay-per-traffic at the moment. Also this old system (as well as some others I maintain) is SXCE-based, and I'm not sure it even supports IPS well enough to update.
The desired option would be for OpenIndiana to allow creating a dataset (named by the user) inside the existing rpool beside the old root, so that the user or (later) some automation scripts can migrate the settings and thus "seem to update" the existing system, and the user can later update the on-disk zpool version for rpool.
Alternatively (or rather as an intermediate solution), please document on the Wiki - what exactly does gui-install do so that users in my situation can properly install from LiveUSB into an existing rpool?