/etc/libvirt/virtlogd.conf

Default Ubuntu 18.04 LTS file not uncommented lines:

cat /etc/libvirt/virtlogd.conf  | grep -v "#" | grep .
(empty)

Default Ubuntu 18.04 LTS /etc/libvirt/virtlogd.conf file

# Master virtlogd daemon configuration file
#

#################################################################
#
# Logging controls
#

# Logging level: 4 errors, 3 warnings, 2 information, 1 debug
# basically 1 will log everything possible
#log_level = 3

# Logging filters:
# A filter allows to select a different logging level for a given category
# of logs
# The format for a filter is one of:
#    x:name
#    x:+name
#      where name is a string which is matched against source file name,
#      e.g., "remote", "qemu", or "util/json", the optional "+" prefix
#      tells libvirt to log stack trace for each message matching name,
#      and x is the minimal level where matching messages should be logged:
#    1: DEBUG
#    2: INFO
#    3: WARNING
#    4: ERROR
#
# Multiple filter can be defined in a single @filters, they just need to be
# separated by spaces.
#
# e.g. to only get warning or errors from the remote layer and only errors
# from the event layer:
#log_filters="3:remote 4:event"

# Logging outputs:
# An output is one of the places to save logging information
# The format for an output can be:
#    x:stderr
#      output goes to stderr
#    x:syslog:name
#      use syslog for the output and use the given name as the ident
#    x:file:file_path
#      output to a file, with the given filepath
#    x:journald
#      ouput to the systemd journal
# In all case the x prefix is the minimal level, acting as a filter
#    1: DEBUG
#    2: INFO
#    3: WARNING
#    4: ERROR
#
# Multiple output can be defined, they just need to be separated by spaces.
# e.g. to log all warnings and errors to syslog under the virtlogd ident:
#log_outputs="3:syslog:virtlogd"
#

# The maximum number of concurrent client connections to allow
# over all sockets combined.
#max_clients = 1024


# Maximum file size before rolling over. Defaults to 2 MB
#max_size = 2097152

# Maximum number of backup files to keep. Defaults to 3,
# not including the primary active file
#max_backups = 3

See also

• libvirt, virtlogd.conf, /etc/libvirt/storage/, libvirt-guests.sh, /etc/libvirt/virtlogd.conf, /var/lib/libvirt/images/
• QEMU: qemu-img, qemu-ga, qemu.conf, virsh qemu, QEMU guest agent (qemu-ga), qcow2, qemu-nbd, qemu-img map, qemu-io, /etc/libvirt/qemu.conf, QEMU releases, VENOM, qemu-nbd --help, qemu-system
• KVM, Installation, QEMU, virsh, virtinst, libguestfs-tools, libvirt, qemu, Red Hat Virtualization (RHV), MacVTap, Virtio, oVirt, KVM services, KVM networking, KVM graphics, CPU, KVM on ARM