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RRDTOOL(1)			    rrdtool			    RRDTOOL(1)

NAME
       rrdtool - Round Robin Database Tool

SYNOPSIS
       rrdtool - [workdir]| function

DESCRIPTION
       OVERVIEW

       It is pretty easy to gather status information from all sorts of
       things, ranging from the	temperature in your office to the number of
       octets which have passed	through	the FDDI interface of your router. But
       it is not so trivial to store this data in an efficient and systematic
       manner. This is where RRDtool comes in handy. It	lets you log and ana-
       lyze the	data you gather	from all kinds of data-sources (DS). The data
       analysis	part of	RRDtool	is based on the	ability	to quickly generate
       graphical representations of the	data values collected over a definable
       time period.

       In this man page	you will find general information on the design	and
       functionality of	the Round Robin	Database Tool (RRDtool). For a more
       detailed	description of how to use the individual functions of RRDtool
       check the corresponding man page.

       For an introduction to the usage	of RRDtool make	sure you consult the
       rrdtutorial.

       FUNCTIONS

       While the man pages talk	of command line	switches you have to set in
       order to	make RRDtool work it is	important to note that RRDtool can be
       remotely	controlled through a set of pipes. This	saves a	considerable
       amount of startup time when you plan to make RRDtool do a lot of	things
       quickly.	Check the section on "Remote Control" further down. There is
       also a number of	language bindings for RRDtool which allow you to use
       it directly from	perl, python, tcl, php,	etc.

       create  Set up a	new Round Robin	Database (RRD).	Check rrdcreate.

       update  Store new data values into an RRD. Check	rrdupdate.

       updatev Operationally equivalent	to update except for output. Check
	       rrdupdate.

       graph   Create a	graph from data	stored in one or several RRDs. Apart
	       from generating graphs, data can	also be	extracted to stdout.
	       Check rrdgraph.

       dump    Dump the	contents of an RRD in plain ASCII. In connection with
	       restore you can use this	to move	an RRD from one	computer ar-
	       chitecture to another.  Check rrddump.

       restore Restore an RRD in XML format to a binary	RRD. Check rrdrestore

       fetch   Get data	for a certain time period from a RRD. The graph	func-
	       tion uses fetch to retrieve its data from an RRD. Check rrd-
	       fetch.

       tune    Alter setup of an RRD. Check rrdtune.

       last    Find the	last update time of an RRD. Check rrdlast.

       info    Get information about an	RRD. Check rrdinfo.

       rrdresize
	       Change the size of individual RRAs. This	is dangerous! Check
	       rrdresize.

       xport   Export data retrieved from one or several RRDs. Check rrdxport

       rrdcgi  This is a standalone tool for producing RRD graphs on the fly.
	       Check rrdcgi.

       HOW DOES	RRDTOOL	WORK?

       Data Acquisition
	       When monitoring the state of a system, it is convenient to have
	       the data	available at a constant	time interval. Unfortunately,
	       you may not always be able to fetch data	at exactly the time
	       you want	to. Therefore RRDtool lets you update the logfile at
	       any time	you want. It will automatically	interpolate the	value
	       of the data-source (DS) at the latest official time-slot	(in-
	       tervall)	and write this interpolated value to the log. The
	       original	value you have supplied	is stored as well and is also
	       taken into account when interpolating the next log entry.

       Consolidation
	       You may log data	at a 1 minute interval,	but you	might also be
	       interested to know the development of the data over the last
	       year. You could do this by simply storing the data in 1 minute
	       intervals for the whole year. While this	would take consider-
	       able disk space it would	also take a lot	of time	to analyze the
	       data when you wanted to create a	graph covering the whole year.
	       RRDtool offers a	solution to this problem through its data con-
	       solidation feature. When	setting	up an Round Robin Database
	       (RRD), you can define at	which interval this consolidation
	       should occur, and what consolidation function (CF) (average,
	       minimum,	maximum, total,	last) should be	used to	build the con-
	       solidated values	(see rrdcreate). You can define	any number of
	       different consolidation setups within one RRD. They will	all be
	       maintained on the fly when new data is loaded into the RRD.

       Round Robin Archives
	       Data values of the same consolidation setup are stored into
	       Round Robin Archives (RRA). This	is a very efficient manner to
	       store data for a	certain	amount of time,	while using a known
	       and constant amount of storage space.

	       It works	like this: If you want to store	1'000 values in	5
	       minute interval,	RRDtool	will allocate space for	1'000 data
	       values and a header area. In the	header it will store a pointer
	       telling which slots (value) in the storage area was last	writ-
	       ten to. New values are written to the Round Robin Archive in,
	       you guessed it, a round robin manner. This automatically	limits
	       the history to the last 1'000 values (in	our example). Because
	       you can define several RRAs within a single RRD,	you can	setup
	       another one, for	storing	750 data values	at a 2 hour interval,
	       for example, and	thus keep a log	for the	last two months	at a
	       lower resolution.

	       The use of RRAs guarantees that the RRD does not	grow over time
	       and that	old data is automatically eliminated. By using the
	       consolidation feature, you can still keep data for a very long
	       time, while gradually reducing the resolution of	the data along
	       the time	axis.

	       Using different consolidation functions (CF) allows you to
	       store exactly the type of information that actually interests
	       you: the	maximum	one minute traffic on the LAN, the minimum
	       temperature of your wine	cellar,	the total minutes of down
	       time, etc.

       Unknown Data
	       As mentioned earlier, the RRD stores data at a constant inter-
	       val. Sometimes it may happen that no new	data is	available when
	       a value has to be written to the	RRD. Data acquisition may not
	       be possible for one reason or other. With RRDtool you can han-
	       dle these situations by storing an *UNKNOWN* value into the
	       database. The value '*UNKNOWN*' is supported through all	the
	       functions of the	tool. When consolidating a data	set, the
	       amount of *UNKNOWN* data	values is accounted for	and when a new
	       consolidated value is ready to be written to its	Round Robin
	       Archive (RRA), a	validity check is performed to make sure that
	       the percentage of unknown values	in the data point is above a
	       configurable level. If not, an *UNKNOWN*	value will be written
	       to the RRA.

       Graphing
	       RRDtool allows you to generate reports in numerical and graphi-
	       cal form	based on the data stored in one	or several RRDs. The
	       graphing	feature	is fully configurable. Size, color and con-
	       tents of	the graph can be defined freely. Check rrdgraph	for
	       more information	on this.

       Aberrant	Behavior Detection
	       by Jake Brutlag

	       RRDtool provides	the building blocks for	near real-time aber-
	       rant behavior detection.	These components include:

	       *   An algorithm	for predicting the value of a time series one
		   time	step into the future.

	       *   A measure of	deviation between predicted and	observed val-
		   ues.

	       *   A mechanism to decide if and	when an	observed value or se-
		   quence of observed values is	too deviant from the predicted
		   value(s).

	       Here is a brief explanation of these components:

	       The Holt-Winters	time series forecasting	algorithm is an	on-
	       line (or	incremental) algorithm that adaptively predicts	future
	       observations in a time series. Its forecast is the sum of three
	       components: a baseline (or intercept), a	linear trend over time
	       (or slope), and a seasonal coefficient (a periodic effect, such
	       as a daily cycle). There	is one seasonal	coefficient for	each
	       time point in the period	(cycle). After a value is observed,
	       each of these components	is updated via exponential smoothing.
	       This means that the algorithm "learns" from past	values and
	       uses them to predict the	future.	The rate of adaptation is gov-
	       erned by	3 parameters, alpha (intercept), beta (slope), and
	       gamma (seasonal). The prediction	can also be viewed as a
	       smoothed	value for the time series.

	       The measure of deviation	is a seasonal weighted absolute	devia-
	       tion. The term seasonal means deviation is measured separately
	       for each	time point in the seasonal cycle. As with Holt-Winters
	       forecasting, deviation is predicted using the measure computed
	       from past values	(but only at that point	in the seasonal	cy-
	       cle). After the value is	observed, the algorithm	learns from
	       the observed value via exponential smoothing. Confidence	bands
	       for the observed	time series are	generated by scaling the se-
	       quence of predicted deviation values (we	usually	think of the
	       sequence	as a continuous	line rather than a set of discrete
	       points).

	       Aberrant	behavior (a potential failure) is reported whenever
	       the number of times the observed	value violates the confidence
	       bands meets or exceeds a	specified threshold within a specified
	       temporal	window (e.g. 5 violations during the past 45 minutes
	       with a value observed every 5 minutes).

	       This functionality is embedded in a set of related RRAs.	In
	       particular, a FAILURES RRA logs potential failures. With	these
	       data you	could, for example, use	a front-end application	to
	       RRDtool to initiate real-time alerts.

	       For a detailed description on how to set	this up, see rrdcre-
	       ate.

       REMOTE CONTROL

       When you	start RRDtool with the command line option '-' it waits	for
       input via standard input	(STDIN). With this feature you can improve
       performance by attaching	RRDtool	to another process (MRTG is one	exam-
       ple) through a set of pipes. Over these pipes RRDtool accepts the same
       arguments as on the command line	and some special commands like quit,
       cd, mkdir and ls. For detailed help on the server commands type:

	  rrdtool help cd|mkdir|pwd|ls|quit

       When a command is completed, RRDtool will print the string  '"OK"',
       followed	by timing information of the form u:usertime s:systemtime.
       Both values are the running totals of seconds since RRDtool was
       started.	If an error occurs, a line of the form '"ERROR:" Description
       of error' will be printed instead. RRDtool will not abort, unless some-
       thing realy serious happens. If a workdir is specified and the UID is
       0, RRDtool will do a chroot to that workdir. If the UID is not 0, RRD-
       tool only changes the current directory to workdir.

       RRD Server

       If you want to create a RRD-Server, you must choose a TCP/IP Service
       number and add them to /etc/services like this:

	rrdsrv	    13900/tcp			    # RRD server

       Attention: the TCP port 13900 isn't officially registered for rrdsrv.
       You can use any unused port in your services file, but the server and
       the client system must use the same port, of course.

       With this configuration you can add RRDtool as meta-server to /etc/in-
       etd.conf. For example:

	rrdsrv stream tcp nowait root /opt/rrd/bin/rrdtool rrdtool - /var/rrd

       Don't forget to create the database directory /var/rrd and reinitialize
       your inetd.

       If all was setup	correctly, you can access the server with perl sock-
       ets, tools like netcat, or in a quick interactive test by using 'telnet
       localhost rrdsrv'.

       NOTE: that there	is no authentication with this feature!	Do not setup
       such a port unless you are sure what you	are doing.

SEE ALSO
       rrdcreate, rrdupdate, rrdgraph, rrddump,	rrdfetch, rrdtune, rrdlast,
       rrdxport

BUGS
       Bugs? Features!

AUTHOR
       Tobias Oetiker <tobi@oetiker.ch>

1.2.30				  2009-01-19			    RRDTOOL(1)

NAME | SYNOPSIS | DESCRIPTION | SEE ALSO | BUGS | AUTHOR

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