This snippet of libvirt XML can be used as a template when creating LXC containers that you want to run/manage via libvirt.

lxc-template

<domain type='lxc'>
  <name>REPLACE</name>
  <memory>327680</memory>
  <os>
    <type>exe</type>
    <init>/sbin/init</init>
  </os>
  <vcpu>1</vcpu>
  <clock offset='utc'/>
  <on_poweroff>destroy</on_poweroff>
  <on_reboot>restart</on_reboot>
  <on_crash>destroy</on_crash>
  <devices>
    <emulator>/usr/lib/libvirt/libvirt_lxc</emulator>
    <filesystem type='mount'>
      <source dir='/var/lib/lxc/REPLACE/rootfs'/>
      <target dir='/'/>
    </filesystem>
    <interface type='network'>
      <source network='default'/>
    </interface>
    <console type='pty'/>
  </devices>
</domain>