rrdgraph - About drawing pretty graphs with rrdtool
rrdtool graph filename [option ...] [data definition ...] [data calculation ...] [variable definition ...] [graph element ...] [print element ...]
The graph function of RRDtool is used to present the data from an RRD to a human viewer. Its main purpose is to create a nice graphical representation but it can also generate a numerical report.
rrdtool graph needs data to work with, use one or more data definition statements to collect this data. You are not limited to one database, it's perfectly legal to collect data from two or more databases (one per statement though).
If you want to display averages, maxima, percentiles etcetera it is best to collect them now using the variable definition statement. Currently this makes no difference but in a future version of rrdtool you may want to collect these values before consolidation.
The data fetched from the RRA is then consolidated so that there is exactly one datapoint per pixel in the graph. If you do not take care yourself, RRDtool will expand the range slightly if necessary (in that case the first and/or last pixel may very well become unknown!).
Sometimes data is not exactly as you would like to display it. For instance, you might be collecting bytes per second but want to display bits per second. This is where the data calculation command is designed for. After consolidating the data, a copy is made and this copy is modified using a rather flexible RPN command set.
When you are done fetching and processing the data, it is time to graph it (or print it). This ends the rrdtool graph sequence.
.png
, .svg
or .eps
but RRDtool does not enforce this.
filename can be '-
' to send the image to stdout
. In
that case, no other output is generated.
The start and end of what you would like to display, and which RRA the data should come from. Defaults are: 1 day ago until now, with the best possible resolution. Start and end can be specified in several formats, see AT-STYLE TIME SPECIFICATION and the rrdgraph_examples manpage. By default, rrdtool graph calculates the width of one pixel in the time domain and tries to get data from an RRA with that resolution. With the step option you can alter this behaviour. If you want rrdtool graph to get data at a one-hour resolution from the RRD, set step to 3600. Note: a step smaller than one pixel will silently be ignored.
A horizontal string at the top of the graph and/or a vertically placed string at the left hand side of the graph.
The width and height of the canvas (the part of the graph with the actual lines and such). Defaults are 400 pixels by 100 pixels.
If you specify the --only-graph option and set the height < 32 pixels you will get a tiny graph image to use as an icon in a potential overview. All labeling will be stripped off the graph.
By default the graph will be autoscaling so that it displays the portion of the y-axis that is actually used. You can change this behaviour by setting the limits. The displayed y-axis will show at least from lower-limit to upper-limit. Autoscaling will still permit those boundaries to be stretched unless the rigid option is set.
[-A|--alt-autoscale]
Sometimes the default algorithm for selecting the y-axis scale is not
performing very well. Normally the scale is selected from a predefined
set of ranges and this fails miserably when you need to graph something
like 260 + 0.001 * sin(x)
. This option calculates the minimum and
maximum y-axis from the actual minimum and maximum values. Our example
would display slightly less than 260-0.001
to slightly more than
260+0.001
(Contributed by Sasha Mikheev).
[-M|--alt-autoscale-max]
Where --alt-autoscale
will modify both the absolute maximum AND minimum
values, this option will only affect the maximum value. The minimum
value, if not defined on the command line, will be 0. This option can
be useful when graphing router traffic when the WAN line uses compression,
and thus the throughput may be higher than the WAN line speed.
[-N|--no-gridfit]
To avoid anti-aliasing effects gridlines are placed on integer pixel values. This is by default done by extending the scale so gridlines happens to be spaced using an integer number of pixels, and starts on integer pixel value. This might extend the scale too much for some logarithmic scales and for linear scales where --alt-autoscale is needed. Using --no-gridfit disables modification of the scale.
[-x|--x-grid none]
The x-axis label is quite complex to configure, if you don't have
very special needs it is probably best to rely on the autoconfiguration
to get this right. You can specify the string none
to skip the grid
and labels altogether.
The grid is defined by specifying a certain amount of time in the ?TM
positions. You can choose from SECOND
, MINUTE
, HOUR
, DAY
,
WEEK
, MONTH
or YEAR
. Then you define how many of these should
pass between each line or label. This pair (?TM:?ST) needs to be
specified for the base grid (G??), the major grid (M??) and the
labels (L??). For the labels you also need to define a precision
in LPR and a strftime format string in LFM. LPR defines
where each label will be placed. If it is zero, the label will be
placed right under the corresponding line (useful for hours, dates
etcetera). If you specify a number of seconds here the label is
centered in this interval (useful for Monday, January etcetera).
--x-grid MINUTE:10:HOUR:1:HOUR:4:0:%X
This places grid lines every 10 minutes, major grid lines every hour and labels every 4 hours. The labels are placed under the major grid lines as they specify exactly that time.
--x-grid HOUR:8:DAY:1:DAY:1:0:%A
This places grid lines every 8 hours, major grid lines and labels each day. The labels are placed exactly between two major grid lines as they specify the complete day and not just midnight.
[-y|--y-grid none]
Y-axis grid lines appear at each grid step interval. Labels are
placed every label factor lines. You can specify -y none
to
skip the grid and labels altogether. The default for this option is
to automatically select sensible values.
[-Y|--alt-y-grid]
Place Y grid dynamically based on graph Y range. Algorithm ensures that you always have grid, that there are enough but not too many grid lines and the grid is metric. That is grid lines are placed every 1, 2, 5 or 10 units. (contributed by Sasha Mikheev)
[-o|--logarithmic]
Logarithmic y-axis scaling.
[-X|--units-exponent value]
This sets the 10**exponent scaling of the y-axis values. Normally values will be scaled to the appropriate units (k, M, etc.). However you may wish to display units always in k (Kilo, 10e3) even if the data is in the M (Mega, 10e6) range for instance. Value should be an integer which is a multiple of 3 between -18 and 18 inclusive. It is the exponent on the units you which to use. For example, use 3 to display the y-axis values in k (Kilo, 10e3, thousands), use -6 to display the y-axis values in u (Micro, 10e-6, millionths). Use a value of 0 to prevent any scaling of the y-axis values.
This option is very effective at confusing the heck out of the default rrdtool autoscaler and grid painter. If rrdtool detects that it is not successful in labeling the graph under the given circumstances, it will switch to the more robust --alt-y-grid mode.
[-L|--units-length value]
How many digits should rrdtool assume the y-axis labels to be ? You may have to use this option to make enough space once you start fideling with the y-axis labeling.
Only generate the graph, if the current graph is out of date or not existent.
[-f|--imginfo printfstr]
After the image has been created, the graph function uses printf together with this format string to create output similar to the PRINT function, only that the printf is supplied with the parameters filename, xsize and ysize. In order to generate an IMG tag suitable for including the graph into a web page, the command line would look like this:
--imginfo '<IMG SRC="/img/%s" WIDTH="%lu" HEIGHT="%lu" ALT="Demo">'
[-c|--color COLORTAG#rrggbb[aa]]
Override the default colors for the standard elements of the graph. The
COLORTAG is one of BACK
background, CANVAS
for the background of
the actual graph, SHADEA
for the left and top border, SHADEB
for the
right and bottom border, GRID
, MGRID
for the major grid, FONT
for
the color of the font, AXIS
for the axis of the graph and finaly ARROW
for the arrow head pointing to the future. Each color is composed out of
three hexadecimal numbers specifying its color component (00 is off, FF is
maximum) of red, green and blue. Optionally you may add another hexadecimal
number specifying the transparency (FF is solid). You may set this option
several times to alter multiple defaults.
A green arrow is made by: --color ARROW:00FF00
[--zoom factor]
Zoom the graphics by the given amount ... The factor must be > 0
[-n|--font FONTTAG:size:font]
Lets you customize which font to use for the various text elements on the
RRD graphs. DEFAULT
sets the default value for all elements TITLE
,
AXIS
for the axis labels, UNIT
for the vertical unit label, LEGEND
for the graph legend.
Use Times for the title: --font TITLE:13:/usr/lib/fonts/times.ttf
RRDtool comes with a preset default font. You can set the environment
variable RRD_DEFAULT_FONT
if you want to change this.
Truetype fonts are only supported for PNG output. See below.
[-a|--imgformat PNG|SVG|EPS|PDF]
Image format for the generated graph. For the vector formats you can choose among the standard Postscript fonts Courier-Bold, Courier-BoldOblique, Courier-Oblique, Courier, Helvetica-Bold, Helvetica-BoldOblique, Helvetica-Oblique, Helvetica, Symbol, Times-Bold, Times-BoldItalic, Times-Italic, Times-Roman, ZapfDingbats
[-i|--interlaced]
If images are interlaced they become visible on browsers more quickly.
[-g|--no-legend]
Suppress generation of legend; only render the graph.
[-F|--force-rules-legend]
Force the generation of HRULE and VRULE legend even if those HRULE or VRULE will not be drawn because out of graph boundaries (mimics behaviour of pre 1.0.42 versions).
[-T|--tabwidth value]
By default the tab-width is 40 pixels, use this option to change it.
[-b|--base value]
If you are graphing memory (and NOT network traffic) this switch should be set to 1024 so that one Kb is 1024 byte. For traffic measurement, 1 kb/s is 1000 b/s.
CDEF:vname=RPN expression
VDEF:vname=RPN expression
You need at least one DEF statement to generate anything. The other statements are useful but optional. See the rrdgraph_data manpage and the rrdgraph_rpn manpage for exact format.
the rrdgraph manpage gives an overview of how rrdtool graph works. the rrdgraph_data manpage describes DEF,CDEF and VDEF in detail, the rrdgraph_rpn manpage describes the RPN language used in the ?DEF statements, the rrdgraph_graph manpage page describes all of the graph and print functions.
Make sure to read the rrdgraph_examples manpage for tips&tricks.
Program by Tobias Oetiker <oetiker@ee.ethz.ch>
This manual page by Alex van den Bogaerdt <alex@ergens.op.het.net>