vnStat is a very simple utility that can track the amount of bandwidth used by your web server. It works by monitoring the received and transmitted bytes counters of your network interface and logging the data in a database. In this post I look at how to install vnStat and a web-based front end on a CentOS Linux web server.

Installing vnStat

• Log in as root: To install vnStat you must log in as root.

• Add RPM repository: vnStat is not available on the default CentOS repositories. So you will have to add the 3rd part repository maintained by Dag Wieers. You do that using the latest rpmforge release. For example:

  32bit CentOS 5:

  rpm -Uhv http://pkgs.repoforge.org/rpmforge-release/rpmforge-release-0.5.2-2.el5.rf.i386.rpm

  rpm -Uhv http://pkgs.repoforge.org/rpmforge-release/rpmforge-release-0.5.2-2.el5.rf.i386.rpm

  64 bit CentOS 6:

  rpm -Uhv http://pkgs.repoforge.org/rpmforge-release/rpmforge-release-0.5.2-2.el6.rf.x86_64.rpm

  rpm -Uhv http://pkgs.repoforge.org/rpmforge-release/rpmforge-release-0.5.2-2.el6.rf.x86_64.rpm

• Install using yum: The next step is to simply use yum to install the vnStat package:

  
yum install vnstat


• Setup database: Before vnStat can begin logging bandwidth usage you need to tell it to setup the database for your network interface. Replace eth0 with the correct interface:

  
vnstat -u -i eth0


  If your using an openvz vps your network interface is usually venet0 or venet1. Doing an

  ifconfig

  will help you identify it.

• Setup correct permissions: vnStat updates its statistics automatically every 5 minutes via a cron job. By default the RPM install sets the permissions for this cron job incorrectly. So edit the /etc/cron.d/vnstat file and replace “nobody” with “root”:

  MAILTO=root

  */5 * * * * root /usr/sbin/vnstat.cron


• Setup correct interface in config file: By default the vnStat cron job will attempt to collect statistics for the eth0 interface. If your network interface is different from that one you will have to modifiy the /etc/sysconfig/vnstat file:

  
VNSTAT_OPTIONS="-i eth3"


• Setup bash alias: Logout of root now and back to your regular user account. If you intend to use vnStat over the command line and your network interface is not eth0 you should setup a bash alias for ease of use in your .bashrc file:

  
alias vnstat="vnstat -i eth3"


Thats about it for the setup.

Using vnStat

Using vnStat is easy since its a simple program.

• Statistics by day

  
vnstat -d


   eth3  /  daily
  
      day         rx      |     tx      |  total
  ------------------------+-------------+----------------------------------------
     22.02.     49.88 GiB |   55.70 GiB |  105.58 GiB  %%%%%:::::
     23.02.    117.31 GiB |  132.10 GiB |  249.42 GiB  %%%%%%%%%%%%:::::::::::::
  ------------------------+-------------+----------------------------------------
   estimated   152.19 GiB |  171.37 GiB |  323.56 GiB
  

• 
  By hour
  

  vnstat -h

  eth3                                                                     18:30
    ^                                                t
    |                                       t  t rt rt  t
    |                                    t rt rt rt rt rt  t
    |                                   rt rt rt rt rt rt rt
    |                                   rt rt rt rt rt rt rt  t
    |                                 t rt rt rt rt rt rt rt rt
    |                        t     t rt rt rt rt rt rt rt rt rt
    |                    rt rt rt rt rt rt rt rt rt rt rt rt rt rt
    |               t rt rt rt rt rt rt rt rt rt rt rt rt rt rt rt rt rt rt
    |  rt rt rt  t rt rt rt rt rt rt rt rt rt rt rt rt rt rt rt rt rt rt rt  t
   -+--------------------------------------------------------------------------->
    |  19 20 21 22 23 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18
  
   h  rx (KiB)   tx (KiB)      h  rx (KiB)   tx (KiB)      h  rx (KiB)   tx (KiB)
  19  1,856,484  2,162,308    03  3,901,273  4,899,191    11 11,237,321 12,284,756
  20  2,102,528  2,310,322    04  4,834,759  5,745,156    12  9,588,273 10,660,528
  21  1,348,942  1,525,638    05  6,264,453  7,334,658    13  7,382,067  8,082,776
  22  1,089,267  1,301,581    06  9,527,424 10,775,408    14  4,160,481  4,556,939
  23  2,252,512  2,747,903    07 10,183,329 11,395,931    15  3,272,184  3,542,964
  00  3,024,305  3,583,757    08 10,959,014 12,136,572    16  2,676,814  3,010,420
  01  4,063,322  4,938,705    09 11,380,338 12,376,197    17  3,018,233  3,421,954
  02  4,764,074  5,811,465    10 11,522,942 12,541,008    18  1,252,560  1,419,053
  

• By month

  vnstat -m

• Live monitoring of the network interface

  vnstat -l

  Monitoring eth3...    (press CTRL-C to stop)
  
     rx:     617.39 KiB/s   756 p/s          tx:     582.82 KiB/s   814 p/s
  
  

vnStat PHP based web frontend

You may find it inconvenient to have to login to your server every time you want to see your server’s bandwidth statistics. To make it easier to see bandwidth stats one kind soul made a PHP frontend that uses vnStat to obtain the necessary data and display it with pretty graphs.

vnStat php frontend requires that you have apache, php and the php-gd image processing library installed. Installing the latter is as easy as running the following command as root:


yum install php-gd


Installing vnStat PHP is pretty straight forward and can be done as a regular user:

• Download it, untar it and place it in a web accessible place like /var/www/html:
  
  wget http://www.sqweek.com/sqweek/files/vnstat_php_frontend-1.4.1.tar.gz

  tar -xzf vnstat_php_frontend-1.4.1.tar.gz

  mkdir /var/www/html/vnstat

  mv vnstat_php_frontend/* /var/www/html/vnstat


• Edit the config.php file: Just set the correct binary name:
  
  $vnstat_bin = 'vnstat';

Then just view the page in your browser by visiting yourdomain.com/vnstat ! You’ll get pretty pictures like below

Bandwidth graphs generated by vnstat php frontend

vnStat is a must have utility for monitoring your system’s bandwidth usage. Its simple to install and use and yet can provide valuable insight.