If you have been seeing unexplained gaps in graphs or maybe whole datasets missing you should upgrade RRDTool.
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Step #1 - Download rrdtool version 1.7.1 from here:
https://oss.oetiker.ch/rrdtool/pub/rrdtool-1.7.1.tar.gz
Step #2 - Remove old rrdtool
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Step #5 - Point NMIS at new rrdtoolInstall the attached uselib.pm in /usr/local/nmis8/lib/NMIS
View file name uselib.pm height 250
Step #6 - Run fix perms
/usr/local/nmis8/admin/fixperms.pl