root@ubuntu-xenial:~# cat /lib/systemd/system/libvirt-bin.service 
+ cat /lib/systemd/system/libvirt-bin.service
[Unit]
Description=Virtualization daemon
Before=libvirt-guests.service
After=network.target
After=dbus.service
After=iscsid.service
After=apparmor.service
After=local-fs.target
After=remote-fs.target
Documentation=man:libvirtd(8)
Documentation=http://libvirt.org

[Service]
Type=notify
EnvironmentFile=-/etc/default/libvirt-bin
ExecStart=/usr/sbin/libvirtd $libvirtd_opts
ExecReload=/bin/kill -HUP $MAINPID
KillMode=process
Restart=on-failure
LimitNOFILE=infinity
LimitNPROC=infinity
TasksMax=infinity

[Install]
WantedBy=multi-user.target
Also=virtlockd.socket
Also=virtlogd.socket