Package: vnstat

"vnstat" package binaries on CentOS:

/usr/bin/vnstat /usr/bin/vnstati /usr/sbin/vnstat.cron /usr/sbin/vnstatd

You may install this package on CentOS with yum install vnstat

"vnstat" package binaries on Debian:

/usr/bin/vnstat /usr/sbin/vnstatd

You may install this package on Debian with apt-get install vnstat