vnstat setup guide/tutorial
yum -y install vnstat
chown nobody.nobody -R /var/lib/vnstat/
#replace venet0 below with your desired interface
#sudo -u nobody vnstat -u -i venet0
sudo -u nobody vnstat --add -i venet0
#in newer versions of vnstat it is not -u but now --add
#edit: vi /etc/sysconfig/vnstat
#VNSTAT_OPTIONS="-i venet0"
# only use the sed below if you are using........