http://oss.oetiker.ch/rrdtool/ http://oss.oetiker.ch/rrdtool/ It's literally the first hit in Google. He probably doesn't explain it because it's a fairly well

http://oss.oetiker.ch/rrdtool/ http://oss.oetiker.ch/rrdtool/ It's literally the first hit in Google. He probably doesn't explain it because it's a fairly well-known tool.