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This article will describe how to install and configure Tobi Oetiker’s MRTG (Multi Router Traffic Grapher) on your Ubuntu home server. Once configured, you’ll be able to use it to monitor the traffic in and out of your home network using the SNMP capability in your network’s gateway/router. MRTG generates static HTML pages containing PNG images which provide a visual representation of this traffic. MRTG typically produces daily, weekly, monthly, and yearly graphs. MRTG is written in perl and works on Unix/Linux as well as Windows. MRTG is free software licensed under the GNU GPL.

So, let’s get started.

Download and Install

First, download and install MRTG using apt-get:

sudo apt-get install mrtg

If this is the first time installing MRTG on your server you’ll likely be presented with the following message. Answering “Yes” means that the default configuration file will be installed with permissions set at 640. Answering “No” means that the permissions are set at 644. In this example we’re going to accept the default Yes. No worries though, if you select No the steps in this tutorial will still work.

MRTG installs a sample configuration file, mrtg.cfg, in /etc. This is the file that will eventually hold the information obtained from your gateway\router. MRTG also creates a directory for the html pages it will serve up at /var/www/mrtg. For a full listing of what MRTG installs and where, run the locate command:

sudo updatedb && locate mrtg

Technically speaking, mrtg.cfg could remain in /etc, but just to keep things tidy, and to help facilitate the startup script that will be created later, let’s create a directory for it and move it into that directory:

sudo mkdir /etc/mrtg && sudo mv /etc/mrtg.cfg /etc/mrtg

That’s it for installing MRTG. Now let’s move on and configure it.

Configure

MRTG includes a script called cfgmaker that will help us populate mrtg.cfg with the information obtained from your gateway/router. But before you run cfgmaker, you should set up the snmp community. This usually involves logging into your gateway/router and enabling SNMP. The default community will typically be “public.” If you change the default community to another name though, make note of it. Now, run the following command, substituting the SNMP community name, if you’ve changed it, and adding the IP address of your gateway/router:

sudo cfgmaker --output /etc/mrtg/mrtg.cfg public@your-router's-IP-address

Next, open mrtg.cfg in a text editor and make sure under Global Configiration Options that “WorkDir: /var/www/mrtg” (under Debian) is uncommented, and under Global Defaults, make sure that “Options[_]: growright, bits” is uncommented. Finally, add the following lines under the Global Defaults section:

RunAsDaemon: Yes
Interval: 5
Logdir: /var/log/
EnableIPv6: no

What does all this do? RunAsDaemon will enable MRTG to…um… run as a daemon. This is beneficial because MRTG is launched only once, thus the parsing of mrtg.cfg file is done only once, not repeatedly as would be the case if one were to run MRTG as a cron task – another acceptable method for running MRTG. Also, when running as a daemon, MRTG itself is responsible for timing the measurement intervals; therefore, we need to add the Interval option and assign it a value – in this case 5 (minutes). This means that every five minutes MRTG will update its graphs.

Speaking of graphs, by default MRTG graphs grow to the left, so by adding the option “growright” the direction of the traffic visible in MRTG’s graphs flips causing the current time to be at the right edge of the graph and the history values to the left of it. We’ve also chosen the “bits” option, which means that the monitored traffic values obtained from your gateway/router are multiplied by 8 and displayed bits per second instead of bytes per second. Finally, we’ve given MRTG a directory to put its log file, and because many routers do not currently support SNMP over IPv6, we’ve shut that off.

Okay, now it’s time to create the web pages which display the MRTG graphs. Run the following command:

sudo indexmaker --output=/var/www/mrtg/index.html /etc/mrtg/mrtg.cfg

MRTG has been configured. Let’s start it up and see what it displays

Start

There’s something important to keep in mind when starting MRTG, and that is that MRTG requires the environmental variable “LANG” to be C in order to run properly. Since most Linux systems these days, including Ubuntu server, use UTF-8 (run echo $LANG to see what your system uses), let’s change LANG to C and start MRTG using the following command:

sudo env LANG=C /usr/bin/mrtg /etc/mrtg/mrtg.cfg

When you run MRTG for the first time you may see a lot of complaints about missing log files. No worries, this is normal for the first 2-3 times you start MRTG this way. If, however, it continues to complain you may want to look into the source of the problem.

Well, that’s it. Now point your browser to http://your-server-address/mrtg and you should see a page that resembles the following. You may have more or less graphs depending on the number interfaces reported by your gateway/router.

Because of the aforementioned options added to mrtg.cfg, you’ll see the graph starting “grow” to the right as the traffic is monitored over time, and the Y axis displayed as bits per second. If you click on any one of these graphs you’ll be taken to another page showing individual graphs for daily, weekly, monthly, and yearly traffic averages, along with the maximum, average, and current bit rate in and out of that particular interface. Only interested in displaying one particular interface? Don’t like the look of the page? No worries, just edit mrtg.cfg and/or /var/www/mrtg until you get it looking the way you want.

Okay, so now that we have MRTG installed, configured and running let’s move on and discuss how to keep it running.

Operate

Starting MRTG by hand is not ideal in the long run. So perhaps after you’ve done some tweaking on MRTG and are satisfied with your results, you can automate the process of running MRTG by creating a startup script in your system startup sequence. Here’s the script that I use:

#!/bin/bash

### START OF SCRIPT
MRTG="/usr/bin/mrtg"
CONFIG="/etc/mrtg/mrtg.cfg"
PIDFILE="/var/run/mrtg.pid"
LOCKFILE="/etc/mrtg/mrtg"
OPTIONS="--daemon"

RETVAL=0

start() {
	echo -n $"Enabling MRTG: "
	rm -f ${LOCKFILE} 2> /dev/null
	env LANG=C ${MRTG} --pid-file=${PIDFILE} --lock-file=${LOCKFILE} ${OPTIONS} ${CONFIG}
	RETVAL=$?
	echo
}

stop() {
	echo -n $"Disabling MRTG: "
	kill `cat ${PIDFILE}` && rm -f ${LOCKFILE}
	RETVAL=$?
	echo
}

restart() {
	stop
	start
}

case "$1" in
  start)
	start
	;;
  stop)
	stop
	;;
  restart|force-reload)
	restart
	;;
  status)
	if [ -f $LOCKFILE ]; then
		echo $"MRTG is enabled."
		RETVAL=0
	else
		echo $"MRTG is disabled."
		RETVAL=3
	fi
	;;
  *)
	echo $"Usage: $0 {start|stop|status|restart|force-reload}"
	exit 1
esac

exit $RETVAL

### END OF SCRIPT

To use this script simply save it as “mrtg” to your home directory. Now make the file executable and move it to /etc/init.d by running the following command:

chmod +x mrtg && sudo mv mrtg /etc/init.d/

Finally, link the script to the appropriate system run-level. For Debian or Ubuntu this should be 2. In most other Linux distributions, it will typically be 4 or 5.

sudo ln -s /etc/init.d/mrtg /etc/rc2.d/S99mrtg
sudo ln -s /etc/init.d/mrtg /etc/rc2.d/K99mrtg

Now, let’s start MRTG using our script. If it’s currently running then substitute restart for start in the following command:

sudo /etc/init.d/mrtg start

That’s it. Now if for some reason your server is rebooted, MRTG should fire up automatically.

Conclusion

This concludes the article on how to install and configure MRTG on Ubuntu server. As you can see, MRTG isn’t terribly complicated and proves to be a really nice open source package for monitoring and displaying traffic in and out your home network from virtually anywhere you have a web browser. For a full list of all the configuration options and other information I encourage you to visit the MRTG web site.

References

http://oss.oetiker.ch/mrtg/doc/index.en.html

Tags: Networking, server, ubuntu