Build two guests:

    $ virt-builder fedora-21 --format qcow2  --update \
        --selinux-relabel --size 40G -o controller.qcow2
  
    $ virt-builder fedora-21 --format qcow2  --update \
        --selinux-relabel --size 40G -o compute.qcow2

(Don't miss to note down the root passwords once the above commands run
successfully)

Import the guests into libvirt:

    $ virt-install --name controller --ram 4096 \
        --disk path=/export/vmimages/controller.qcow2,cache=writeback,format=qcow2 \
        --network network=openstackvms \
        --os-variant=fedora21 --nographics --serial=pty --import

    $ virt-install --name compute --ram 4096 \
        --disk path=/export/vmimages/compute.qcow2,cache=writeback,format=qcow2 \
        --network network=openstackvms \
        --os-variant=fedora21 --nographics --serial=pty --import