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A very simple script to merge multiple RRD files, since none of those available seem to work.
#!/usr/bin/env python
"""Simple script to merge multiple RRD files together.
Accepts any number of RRD file names as arguments. Produces an "rrdtool dump"
style file on stdout. The last RRD file should have a slot for every possible
record in the resulting merged RRD.
Run something like:
$ python filea.rrd fileb.rrd filec.rrd | \
rrdtool restore /dev/stdin merged.rrd
import re
import subprocess
import sys
def main():
rrd_data = {}
rrds = sys.argv[1:]
last_rrd = len(rrds) - 1
for i, rrdname in enumerate(rrds):
p = subprocess.Popen(
('rrdtool', 'dump', rrdname), stdout=subprocess.PIPE)
for j, line in enumerate(p.stdout):
m ='<cf>(.*)</cf>', line)
if m:
cf =
m ='<pdp_per_row>(.*)</pdp_per_row>', line)
if m:
pdp =
m =' / (\d+) --> (.*)', line)
if m:
k = cf + pdp
rrd_data.setdefault(k, {})
if ('NaN' not in or ( not in rrd_data[k]):
rrd_data[k][] = line
line = rrd_data[k][]
if i == last_rrd:
print line.rstrip()
if __name__ == '__main__':
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okki-linux commented May 12, 2012

how to work this scipt ?

ex : old.rrd new.rrd merged.rrd

i use this not working .

ERROR: opening 'argo.rrd': No such file or directory

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arantius commented May 13, 2012

Well, first, the files need to actually exist. The first through second-to-last should be the sources, possibly overlapping in time, to be combined. The last should be a larger set, going back far enough to contain all of the data for the earlier files. Probably by "rrdtool resize ... GROW" on the newest file.

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mcdarren commented Jul 4, 2012


Would you happen to still have a copy of the perl script ( you referred to at ?
I would like to have a look at this script, and possibly fix it, but I'm having difficulty finding a copy.

many thanks,

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Sieberkev commented Jan 29, 2015

Thanks a lot, works like a charm 😃

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fuhbar commented Sep 2, 2015

Thanks pal for your fantastic work, you saved my life today!

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4zap commented May 7, 2016

This script made my day! Awesome! :)

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fanto666 commented Dec 11, 2017

This tool does not properly work with RRDs generated by smokeping.
The reason is apparently that smokeping RRD's have "uptime" record that is NaN all the time.
to merge smokeping RRDs, we need to check if all columns are "NaN", not only one (since that test will always be true).

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TuningYourCode commented Feb 7, 2018

Thx for the script :)
Used it to merge munin history (not beautiful at all):

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drew-holt commented May 29, 2018

Worked great for combining nagiosgraph! PING*pl.rrd | rrdtool restore /dev/stdin pl.rrd

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kungfoochef commented Feb 7, 2019

Thank you for this @arantius, worked perfectly.

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famantanantsoaandry commented Mar 10, 2020

thank you , it is working properly

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salehhoushangi commented Apr 28, 2020

hi . i use this command as below
python old/pop_site_tavanir04_traffic_in_28871.rrd new/pop_site_tavanir04_traffic_in_28871.rrd | rrdtool restore /dev/stdin merged.rrd
but i got this error:
ERROR: mmaping file 'old/pop_site_tavanir04_traffic_in_28871.rrd': Invalid argument

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salehhoushangi commented Apr 28, 2020

i want to merge rrd file because i have gap between out graph

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