Vnstat

Vnstat is a command line based network usage monitoring tool. It is capable of showing the current network utilization as well as providing historical data.

Installation

On Red Hat/Fedora based systems, vnstat should be available from the main repository. For older versions of Red Hat such as CentOS 6, it is available from the EPEL repository.

Installing from Source

The following instructions will set up vnstat from source and should work for CentOS/ScientificLinux/RHEL linux distributions.

# wget http://humdi.net/vnstat/vnstat-1.11.tar.gz
# tar -xzf vnstat-1.11.tar.gz
# cd vnstat-1.11
# make
# make install
# vnstat --testkernel
# /bin/cp examples/init.d/centos/vnstat /etc/init.d/vnstat
# chkconfig --levels 234 --add vnstat
# vnstat -u -i eth0
# /etc/init.d/vnstat start

Configuration

Vnstat makes use of a daemon to record network traffic into databases stored in /var/lib/vnstat as well as a cronjob running at 5 minute intervals defined at /etc/cron.d/vnstat.

By default, vnstat will only monitor eth0. You will need to adjust the /etc/sysconfig/vnstat and /etc/vnstat.conf configuration files accordingly.

You will also need to initialize the interface database by running vnstat -u -i $InterfaceName, otherwise the daemon and cronjob will not record any data.

Force Update

If the cronjob fails for some reason, you may force an update by running:

# sudo -u /usr/sbin/vnstat.cron --force

Usage

Here are some example uses with vnstat.

Show Live Traffic Statistics

To show the live traffic in bytes (rate unit option -ru 0)

# vnstat -l -ru 0
(press CTRL-C to stop)

   rx:     40.08 MiB/s 28784 p/s          tx:      3.20 MiB/s  9378 p/s^C


 enp3s0  /  traffic statistics

                           rx         |       tx
--------------------------------------+------------------
  bytes                     1.16 GiB  |      109.45 MiB
--------------------------------------+------------------
          max            49.68 MiB/s  |      4.58 MiB/s
      average            39.54 MiB/s  |      3.65 MiB/s
          min            33.13 MiB/s  |      1.38 MiB/s
--------------------------------------+------------------
  packets                     859772  |          289093
--------------------------------------+------------------
          max              35996 p/s  |       12085 p/s
      average              28659 p/s  |        9636 p/s
          min              24495 p/s  |        8353 p/s
--------------------------------------+------------------
  time                    30 seconds

Show Usage by Month

# vnstat -d

Issues

Not Enough Data

You may get the following error if your interface is not being recorded:

enp3s0: Not enough data available yet.

Ensure that the cronjob and daemon is active and running. Check by running ps -eaf. There should be at least noe vnstat daemon running.