libvirt users - Oct 2017 - libvirtd audit log

Hi

   I according to libvirt.org Audit log guide ,I install auditd in my
system(ubuntu 16.04.2), but when I operate guest running in host, I can't
not find guest audit log in /var/log/audit/audit.log, audit_level=1.
  when I change audit_level=2, I restart libvirtd, libvirtd start failed.
  Thanks