vnstat is a console-based network traffic monitor. It keeps a log of hourly, daily and monthly network traffic for the selected interface(s). The traffic information is analyzed from the proc filesystem. That way vnStat can be used even without root permissions.

First you will need to install the epel repository
You can then install the tool with

yum install vnstat

runuser -l vnstat -g vnstat -c '/usr/bin/vnstat -u -i eth0'

chsh -s /sbin/nologin vnstat

vnstat -i eth0

vnstat -i eth0 -d

vnstat -i eth0 -l