Here's the disk option I'm giving to virt-install:
--disk pool=libvirt-pool,size=4,bus=virtio
(I'm also using "--os-variant=ubuntulucid".)
I've been able to install a new VM using the IDE storage driver first and then switch to virtio after the installation is complete, but it would simplify the process if it could start with virtio right off the bat.
I'm using Ubuntu 10.04 LTS ("Lucid") host and guest, which provides libvirt 0.7.5 and kernel 2.6.32.
I'm about ready to concede defeat and set up a way to automate making the change after the installation, but I thought I'd ask here first. Thanks!
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Brian