Monitoring bandwidth usage with vnStat under CentOS Linux

February 24th, 2010

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

    64 bit CentOS 6:

    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

vnstat php frontend
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.

10 Responses to “Monitoring bandwidth usage with vnStat under CentOS Linux”

  1. Richard says:

    Thanks – a really useful post, I gave up with trying to figure this out from the vnstat homepage.

    I installed from the epel repository and I didn’t have to replace nobody with root in /etc/cron.d/vnstat but I did have to uncomment the line below to enable the monitoring.

    Posted on 21 May 2010 Reply
  2. Mike says:

    Rather than setting a bash alias, if you want to change the default interface system wide, simply edit /etc/vnstat.conf and change:

    Interface “eth0″

    to

    Interface “eth3″

    I should also mention, the EPEL package installs the /etc/cron.d/vnstat file with the vnstat command commented out. So you’ll need to edit /etc/cron.d/vnstat and uncomment the command to get the 5 minute updates.

    Oh, and the EPEL package also creates and uses a new user ‘vnstat’, so no need to modify the user in the cron file.

    Posted on 08 Oct 2010 Reply
  3. Tony says:

    Awesome post, thank you for making it a little easier to use Linux!

    Posted on 06 Nov 2010 Reply
  4. Florian says:

    Thanks for this post man, it really helped me out! Keep feeding us with topics like that.

    BR

    Posted on 28 Feb 2011 Reply
  5. Igor Bicanic says:

    Useful post. In my case I had to restart the cron service after the configurations.
    “service crond restart”

    Posted on 16 Mar 2011 Reply
  6. Periklis says:

    Thanks for this, it really helped me. For anyone interested, please note that the latest version of the php frontend is now 1.5.1

    Posted on 10 Jan 2012 Reply
  7. Preqitiew says:

    how to configure vnstat to log 2 or more network card, i.e eth0, eth1, eth1:1. thanks

    Posted on 23 Feb 2012 Reply
    • Abdussamad says:

      Setup an additional cron job to run vnstat -u -i {interface}

      Posted on 25 Feb 2012 Reply
  8. Jazz says:

    Hi.

    On CentOS 5.5 i did not need to run it as root. However make sure that the databases in /var/libvnstat are owned by nobody.nobody after creating them with the -i -u parameters.

    Also for setting up monitoring for multiple databases i did not have to make multiple cron jobs or configs. Just creating the databases is enough.

    Thanks for the tutorial.

    Posted on 23 Jul 2012 Reply

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