launch the unit service as the unprivileged user vnstat
--- a/examples/systemd/simple/vnstat.service
+++ b/examples/systemd/simple/vnstat.service
@@ -4,6 +4,7 @@
 After=network.target
 
 [Service]
+User=vnstat
 ExecStart=/usr/sbin/vnstatd --nodaemon
 ExecReload=/bin/kill -HUP $MAINPID
 Restart=on-failure