How to reset munin graphs
Munin data is stored in Round Robin Database files (.rrd). These are stored under /var/lib/munin.
Each host and hostgroup will have it's own subdirectory under /var/lib/munin
Delete the .rrd files under the hostname in question, and your data will be zeroed out. Graphs will be re-generated after a few minutes.
Or alternatively if you just want to fix the data in the RRD files (for example spike on the network graph on the server reboot), just run:
rrddtool dump /var/lib/munin/xy/z.rrd >z.xml
edit the data in xml file (fix big values, but remember they are in scientific notation) and then just re-create the RRD file:
rrdtool restore z.xml x.rrd
and overwrite the original RRD with this new one. Using this, you can fix the values and still preserve your old data.
EDIT: You can find detailed description and howto here: http://munin-monitoring.org/wiki/SpikeRemoval
Yes, delete all the
*.rrd files in the folder
where munin generates the graphs (where the .html files are).
/var/lib/munin/xyz/. It's defined in your munin.conf (dbdir).
The rrd files are regenerated on the next run.
You should also remove the html files that have been created. They are usually located under /var/www/munin/. In that directory, you will find your hostgroup directories. delete the .png files and the .html file of the graph you want to reset.