This commit changes the behavior of LIBVIRT_DEBUG=1 libvirtd:
$ git show 7022b09111
commit 7022b09111
Author: Daniel P. Berrange <berrange@redhat.com>
Date: Thu Sep 27 13:13:09 2012 +0100
Automatically enable systemd journal logging
Probe to see if the systemd journal is accessible, and if
so enable logging to the journal by default, rather than
stderr (current default under systemd).
Previously 'LIBVIRT_DEBUG=1 /usr/sbin/libvirtd' would show all debug
output to stderr, now it send debug output to the journal.
Only use the journal by default if running in daemon mode, or
if stdin is _not_ a tty. This should make libvirtd launched from
systemd use the journal, but preserve the old behavior in most
situations.