[Nottingham] MRTG

Graeme Fowler graeme at graemef.net
Thu Aug 3 08:05:23 BST 2006

On Wed, 2006-08-02 at 19:33 +0200, Johan Boshoff wrote:
> I want to monitor my traffic going in and out of my server and loaded MRTG 
> but when I configure it, I don't know what to put in as the 
> community at router.  I tried the default and IP's and Host names, etc, but it 
> just don;t want to work.

Unless you have also installed, configured, and secured an SNMP daemon
on your machine it is likely you'll have to use an external script to
pass your local interface usage to MRTG.

The defaults in the delivered config file are just examples, and IIRC
are all commented out anyway so won't do a thing no matter how hard you

You'll more than likely need an MRTG config file in /etc/mrtg/mrtg.conf
like this one:

WorkDir: /var/www/html/traffic
ThreshDir: /var/www/html/traffic/thresholds
Options[_]: bits, growright
YLegend[_]: bits/second
ShortLegend[_]: b/s
LegendI[_]:  In:
LegendO[_]:  Out:
Forks: 5

Target[eth1]: `/usr/local/bin/local-dev.pl eth0`
MaxBytes[eth1]: 12500000
AbsMax[eth1]: 12500000
Title[eth1]: gw.graemef.net eth0 (external)
PageTop[eth1]: <H2>gw.graemef.net eth0 (external)</H2>

...and a script to call in /usr/local/bin/local-dev.pl like so:

# usage:
# /usr/local/bin/local-dev.pl devname

$devname = @ARGV[0];

exit (255) if ($devname !~ /^(eth|tun|vlan)[0-9]/);

open INPUT, "/bin/cat /proc/net/dev|" or die "Oops. Could not
open /proc/net/dev for reading: $!\n";

while (<INPUT>) {
  next unless (m/$devname/);
  my ($rbyte,$rpack,$rerr,$rdrop,$rfifo,$rframe,$rcomp,$rmult,$tbyte,
$tpack,$terr,$tdrop,$tfifo,$tframe,$tcomp,$tmult) = split(/\s+/);
  print "$rbyte\n$tbyte\n$uptime\n$devname\n";


That's worked for me for years. It's probably not very elegant and other
list members might smite me for doing things terribly inefficiently
(hell, I could replace the whole caboodle with one line of awk these
days) but it does work.

Again, reading those docs will help you out. MRTG is probably one of the
best documented OSS applications available IMO. And I provide Tobi with
a mirror site for it :)


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