Blame doc/mrtg.pod

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=head1 NAME
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mrtg - What is MRTG ?
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=head1 DESCRIPTION
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The Multi Router Traffic Grapher (MRTG) is a tool to monitor
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the traffic load on network links.  MRTG generates HTML pages
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containing PNG images which provide a LIVE visual representation of
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this traffic.
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Go to http://oss.oetiker.ch/mrtg for all the details about mrtg.
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=head1 HIGHLIGHTS
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=over
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=item Portable
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MRTG works on most UNIX platforms and Windows NT.
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=item Perl
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MRTG is written in Perl and comes with full source.
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=item Portable SNMP
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MRTG Uses a highly portable SNMP implementation written entirely in
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Perl (thanks to Simon Leinen). There is no need to install any
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external SNMP package.
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=item SNMPv2c support
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MRTG can read the new SNMPv2c 64bit counters. No more counter wrapping.
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=item Reliable Interface Identification
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Router interfaces can be identified by IP address, description and
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ethernet address in addition to the normal interface number.
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=item Constant size Logfiles
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MRTG's logfiles do NOT grow thanks to the use of a unique data
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consolidation algorithm.
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=item Automatic Configuration
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MRTG comes with a set of configuration tools which make configuration and
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setup very simple.
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=item Performance
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Time critical routines are written in C (thanks to the initiative
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of Dave Rand my Co-Author).
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=item GIF free Graphics
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Graphics are generated directly in PNG format using the
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GD library by Thomas Boutell.
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=item Customizability
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The look of the webpages produced by MRTG is highly configurable.
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=item RRDtool
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MRTG has built-in hooks for using RRDtool. If you are strapped for
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performance this may help.
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=back
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=head1 DETAILS
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MRTG consists of a Perl script which uses SNMP to read the traffic
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counters of your routers and a fast C program which logs the traffic
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data and creates beautiful graphs representing the traffic on the
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monitored network connection. These graphs are embedded into webpages
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which can be viewed from any modern Web-browser.
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In addition to a detailed daily view, MRTG also creates visual
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representations of the traffic seen during the last seven days, the
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last five weeks and the last twelve months. This is possible because
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MRTG keeps a log of all the data it has pulled from the router. This
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log is automatically consolidated so that it does not grow over time,
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but still contains all the relevant data for all the traffic seen over
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the last two years.  This is all performed in an efficient manner.
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Therefore you can monitor 200 or more network links from any halfway
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decent UNIX box.
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MRTG is not limited to monitoring traffic, though.  It is possible to
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monitor any SNMP variable you choose. You can even use an
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external program to gather the data which should be monitored via
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MRTG. People are using MRTG, to monitor things such as System Load,
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Login Sessions, Modem availability and more. MRTG even allows you to
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accumulate two or more data sources into a single graph.
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=head1 HISTORY
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In 1994 I was working at a site where we had one
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64kbit line to the outside world. Obviously, everybody was interested
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in knowing how the link was performing. So I wrote a quick hack which
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created a constantly updated graph on the web that showed the traffic
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load on our Internet link. This eventually evolved into a rather
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configurable Perl script called MRTG-1.0 which I released in spring
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1995. After a few updates, I left my job at DMU to start work at the
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Swiss Federal Institute of Technology. Due to lack of time I had to
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put MRTG aside. One day in January of 1996, I received email from
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Dave Rand asking if I had any ideas why MRTG was so slow. Actually, I
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did. MRTG's programming was not very efficient and it was written
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entirely in Perl. After a week or so, Dave wrote back to me and said
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he had tried what I had suggested for improving MRTG's speed. Since
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the changes did not help much, he had decided to rewrite the
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time-critical sections of MRTG in C. The code was attached to his
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email. His tool increased the speed of MRTG by a factor of 40! This
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got me out of my 'MRTG ignorance' and I started to spend my spare time
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developing of MRTG-2.
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Soon after MRTG-2 development had begun I started to give beta
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copies to interested parties. In return I got many feature patches, a
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lot of user feedback and bug fixes. The product you are getting now
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wouldn't be in this state if it hadn't been for the great contributions
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and support I received from of many people. I would like
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to take this opportunity to thank them all. (See the files CHANGES for a
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long list of folk people who helped to make MRTG what it is today.)
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=head1 Command-line
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Mrtg is also the name of the script you have to run to poll data and
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generate the graphs. Most configuration is set through the configuration
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file; some command-line options exist all the same.
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=over
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=item B<--user> I<username>  and B<--group> I<groupname>
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Run as the given user and/or group. (Unix Only)
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=item B<--lock-file> I<filename>
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Use an alternate lock-file (the default is to use the configuration-file
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appended with C<_l>).
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=item B<--confcache-file> I<filename>
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Use an alternate confcache-file (the default is to use the configuration-file appended with C<.ok>)
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=item B<--logging> I<filename>|B<eventlog>
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If this is set to writable filename, all output from mrtg (warnings, debug messages, errors)
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will go to I<filename>. If you are running on Win32 you can specify B<eventlog> instead of a filename
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which will send all error to the windows event log.
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B<NOTE:>Note, there is no Message DLL for mrtg. This has the side effect
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that the windows event logger will display a nice message with every entry
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in the event log, complaing about the fact that mrtg has no message dll. If
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any of the Windows folks want to contribute one, they are welcome.
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=item B<--daemon>
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Put MRTG into the background, running as a daemon. This works the same way as
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the config file option, but the switch is required for proper FHS operation  
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(because /var/run is writable only by root)
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=item B<--fhs>
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Configure all mrtg paths to conform to the FHS specification
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L<http://www.pathname.com/fhs/>. The following default values are assumed:
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 confcachefile - /var/cache/mrtg/mrtg.ok
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 pid-file      - /var/run/mrtg.pid
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 lock-file     - /var/cache/mrtg/mrtg.lck
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 log-file      - /var/log/mrtg.log 
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=item B<--check>
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Only check the cfg file for errors. Do not do anything.
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=item B<--pid-file=s>
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Define the name and path of the pid file for mrtg running as a daemon
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=item B<--log-only>
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Only update the logfile, do not produce graphics or html pages
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=item B<--debug=s>
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Enable debug options. The argument of the debug option is a comma separated list of debug values:
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 cfg  - watch the config file reading
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 dir  - directory mangeling
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 base - basic program flow 
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 tarp - target parser
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 snpo - snmp polling 
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 fork - forking view 
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 time - some timing info
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 log  - logging of data via rateup or rrdtool
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Example:
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 --debug="cfg,snpo"
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=back
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=head1 READ ON
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Learn more about MRTG by going to the mrtg home page on:
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http://oss.oetiker.ch/mrtg
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=head1 AUTHOR
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Tobias Oetiker E<lt>tobi@oetiker.chE<gt> and many contributors