1RRDTOOL(1)                          rrdtool                         RRDTOOL(1)
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NAME

6       rrdtool - Round Robin Database Tool
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SYNOPSIS

9       rrdtool - [workdir]| function
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DESCRIPTION

12   OVERVIEW
13       It is pretty easy to gather status information from all sorts of
14       things, ranging from the temperature in your office to the number of
15       octets which have passed through the FDDI interface of your router. But
16       it is not so trivial to store this data in an efficient and systematic
17       manner. This is where RRDtool comes in handy. It lets you log and
18       analyze the data you gather from all kinds of data-sources (DS). The
19       data analysis part of RRDtool is based on the ability to quickly
20       generate graphical representations of the data values collected over a
21       definable time period.
22
23       In this man page you will find general information on the design and
24       functionality of the Round Robin Database Tool (RRDtool). For a more
25       detailed description of how to use the individual functions of RRDtool
26       check the corresponding man page.
27
28       For an introduction to the usage of RRDtool make sure you consult the
29       rrdtutorial.
30
31   FUNCTIONS
32       While the man pages talk of command line switches you have to set in
33       order to make RRDtool work it is important to note that RRDtool can be
34       remotely controlled through a set of pipes. This saves a considerable
35       amount of startup time when you plan to make RRDtool do a lot of things
36       quickly. Check the section on "REMOTE CONTROL" further down. There is
37       also a number of language bindings for RRDtool which allow you to use
38       it directly from Perl, python, Tcl, PHP, etc.
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40       create  Set up a new Round Robin Database (RRD). Check rrdcreate.
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42       update  Store new data values into an RRD. Check rrdupdate.
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44       updatev Operationally equivalent to update except for output. Check
45               rrdupdate.
46
47       graph   Create a graph from data stored in one or several RRDs. Apart
48               from generating graphs, data can also be extracted to stdout.
49               Check rrdgraph.
50
51       graphv  Create a graph from data stored in one or several RRDs. Same as
52               graph, but metadata are printed before the graph. Check
53               rrdgraph.
54
55       dump    Dump the contents of an RRD in plain ASCII. In connection with
56               restore you can use this to move an RRD from one computer
57               architecture to another.  Check rrddump.
58
59       restore Restore an RRD in XML format to a binary RRD. Check rrdrestore
60
61       fetch   Get data for a certain time period from a RRD. The graph
62               function uses fetch to retrieve its data from an RRD. Check
63               rrdfetch.
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65       tune    Alter setup and structure of an RRD. Check rrdtune.
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67       first   Find the first update time of an RRD. Check rrdfirst.
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69       last    Find the last update time of an RRD. Check rrdlast.
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71       lastupdate
72               Find the last update time of an RRD. It also returns the value
73               stored for each datum in the most recent update. Check
74               rrdlastupdate.
75
76       info    Get information about an RRD. Check rrdinfo.
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78       resize  Change the size of individual RRAs. This is dangerous! Check
79               rrdresize.
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81       xport   Export data retrieved from one or several RRDs. Check rrdxport.
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83       flushcached
84               Flush the values for a specific RRD file from memory. Check
85               rrdflushcached.
86
87       list    List the directories and rrd databases remotely. Check rrdlist.
88
89   HOW DOES RRDTOOL WORK?
90       Data Acquisition
91               When monitoring the state of a system, it is convenient to have
92               the data available at a constant time interval. Unfortunately,
93               you may not always be able to fetch data at exactly the time
94               you want to. Therefore RRDtool lets you update the log file at
95               any time you want. It will automatically interpolate the value
96               of the data-source (DS) at the latest official time-slot
97               (interval) and write this interpolated value to the log. The
98               original value you have supplied is stored as well and is also
99               taken into account when interpolating the next log entry.
100
101       Consolidation
102               You may log data at a 1 minute interval, but you might also be
103               interested to know the development of the data over the last
104               year. You could do this by simply storing the data in 1 minute
105               intervals for the whole year. While this would take
106               considerable disk space it would also take a lot of time to
107               analyze the data when you wanted to create a graph covering the
108               whole year. RRDtool offers a solution to this problem through
109               its data consolidation feature. When setting up a Round Robin
110               Database (RRD), you can define at which interval this
111               consolidation should occur, and what consolidation function
112               (CF) (average, minimum, maximum, last) should be used to build
113               the consolidated values (see rrdcreate). You can define any
114               number of different consolidation setups within one RRD. They
115               will all be maintained on the fly when new data is loaded into
116               the RRD.
117
118       Round Robin Archives
119               Data values of the same consolidation setup are stored into
120               Round Robin Archives (RRA). This is a very efficient manner to
121               store data for a certain amount of time, while using a known
122               and constant amount of storage space.
123
124               It works like this: If you want to store 1'000 values in 5
125               minute interval, RRDtool will allocate space for 1'000 data
126               values and a header area. In the header it will store a pointer
127               telling which slots (value) in the storage area was last
128               written to. New values are written to the Round Robin Archive
129               in, you guessed it, a round robin manner. This automatically
130               limits the history to the last 1'000 values (in our example).
131               Because you can define several RRAs within a single RRD, you
132               can setup another one, for storing 750 data values at a 2 hour
133               interval, for example, and thus keep a log for the last two
134               months at a lower resolution.
135
136               The use of RRAs guarantees that the RRD does not grow over time
137               and that old data is automatically eliminated. By using the
138               consolidation feature, you can still keep data for a very long
139               time, while gradually reducing the resolution of the data along
140               the time axis.
141
142               Using different consolidation functions (CF) allows you to
143               store exactly the type of information that actually interests
144               you: the maximum one minute traffic on the LAN, the minimum
145               temperature of your wine cellar, ... etc.
146
147       Unknown Data
148               As mentioned earlier, the RRD stores data at a constant
149               interval. Sometimes it may happen that no new data is available
150               when a value has to be written to the RRD. Data acquisition may
151               not be possible for one reason or other. With RRDtool you can
152               handle these situations by storing an *UNKNOWN* value into the
153               database. The value '*UNKNOWN*' is supported through all the
154               functions of the tool. When consolidating a data set, the
155               amount of *UNKNOWN* data values is accounted for and when a new
156               consolidated value is ready to be written to its Round Robin
157               Archive (RRA), a validity check is performed to make sure that
158               the percentage of unknown values in the data point is above a
159               configurable level. If not, an *UNKNOWN* value will be written
160               to the RRA.
161
162       Graphing
163               RRDtool allows you to generate reports in numerical and
164               graphical form based on the data stored in one or several RRDs.
165               The graphing feature is fully configurable. Size, color and
166               contents of the graph can be defined freely. Check rrdgraph for
167               more information on this.
168
169       Aberrant Behavior Detection
170               by Jake Brutlag
171
172               RRDtool provides the building blocks for near real-time
173               aberrant behavior detection. These components include:
174
175               •   An algorithm for predicting the value of a time series one
176                   time step into the future.
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178               •   A measure of deviation between predicted and observed
179                   values.
180
181               •   A mechanism to decide if and when an observed value or
182                   sequence of observed values is too deviant from the
183                   predicted value(s).
184
185               Here is a brief explanation of these components:
186
187               The Holt-Winters time series forecasting algorithm is an on-
188               line (or incremental) algorithm that adaptively predicts future
189               observations in a time series. Its forecast is the sum of three
190               components: a baseline (or intercept), a linear trend over time
191               (or slope), and a seasonal coefficient (a periodic effect, such
192               as a daily cycle). There is one seasonal coefficient for each
193               time point in the period (cycle). After a value is observed,
194               each of these components is updated via exponential smoothing.
195               This means that the algorithm "learns" from past values and
196               uses them to predict the future. The rate of adaptation is
197               governed by 3 parameters, alpha (intercept), beta (slope), and
198               gamma (seasonal). The prediction can also be viewed as a
199               smoothed value for the time series.
200
201               The measure of deviation is a seasonal weighted absolute
202               deviation. The term seasonal means deviation is measured
203               separately for each time point in the seasonal cycle. As with
204               Holt-Winters forecasting, deviation is predicted using the
205               measure computed from past values (but only at that point in
206               the seasonal cycle). After the value is observed, the algorithm
207               learns from the observed value via exponential smoothing.
208               Confidence bands for the observed time series are generated by
209               scaling the sequence of predicted deviation values (we usually
210               think of the sequence as a continuous line rather than a set of
211               discrete points).
212
213               Aberrant behavior (a potential failure) is reported whenever
214               the number of times the observed value violates the confidence
215               bands meets or exceeds a specified threshold within a specified
216               temporal window (e.g. 5 violations during the past 45 minutes
217               with a value observed every 5 minutes).
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219               This functionality is embedded in a set of related RRAs. In
220               particular, a FAILURES RRA logs potential failures. With these
221               data you could, for example, use a front-end application to
222               RRDtool to initiate real-time alerts.
223
224               For a detailed description on how to set this up, see
225               rrdcreate.
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227   REMOTE CONTROL
228       When you start RRDtool with the command line option '-' it waits for
229       input via standard input (STDIN). With this feature you can improve
230       performance by attaching RRDtool to another process (MRTG is one
231       example) through a set of pipes. Over these pipes RRDtool accepts the
232       same arguments as on the command line and some special commands like
233       cd, mkdir, pwd, ls and quit. For detailed help on the server commands
234       type:
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236          rrdtool help cd
237
238       When a command is completed, RRDtool will print the string  '"OK"',
239       followed by timing information of the form u:usertime s:systemtime.
240       Both values are the running totals of seconds since RRDtool was
241       started. If an error occurs, a line of the form '"ERROR:" Description
242       of error' will be printed instead. RRDtool will not abort, unless
243       something really serious happens. If a workdir is specified and the UID
244       is 0, RRDtool will do a chroot to that workdir. If the UID is not 0,
245       RRDtool only changes the current directory to workdir.
246
247   RRD Server
248       If you want to create a RRD-Server, you must choose a TCP/IP Service
249       number and add them to /etc/services like this:
250
251        rrdsrv      13900/tcp                       # RRD server
252
253       Attention: the TCP port 13900 isn't officially registered for rrdsrv.
254       You can use any unused port in your services file, but the server and
255       the client system must use the same port, of course.
256
257       With this configuration you can add RRDtool as meta-server to
258       /etc/inetd.conf. For example:
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260        rrdsrv stream tcp nowait root /opt/rrd/bin/rrdtool rrdtool - /var/rrd
261
262       Don't forget to create the database directory /var/rrd and reinitialize
263       your inetd.
264
265       If all was setup correctly, you can access the server with Perl
266       sockets, tools like netcat, or in a quick interactive test by using
267       'telnet localhost rrdsrv'.
268
269       NOTE: that there is no authentication with this feature! Do not setup
270       such a port unless you are sure what you are doing.
271

RRDCACHED, THE CACHING DAEMON

273       For very big setups, updating thousands of RRD files often becomes a
274       serious IO problem. If you run into such problems, you might want to
275       take a look at rrdcached, a caching daemon for RRDtool which may help
276       you lessen the stress on your disks.
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SEE ALSO

279       rrdcreate, rrdupdate, rrdgraph, rrddump, rrdfetch, rrdtune, rrdlast,
280       rrdxport, rrdflushcached, rrdcached
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BUGS

283       Bugs? Features!
284

AUTHOR

286       Tobias Oetiker <tobi@oetiker.ch>
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2901.8.0                             2022-03-14                        RRDTOOL(1)
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