One proverb says: you can watch three things forever: water flowing, fire flaming and rrdtool drawing graphs. This post is about the latter. So what is rrdtool? rddtool — is a wonderful utility, that allows to manipulate the data, stored in rrd (round-robin database). This format is notable for being initially designed for storing periodic information, keeping database size fixed (rather small) independently of data quantity, but you still have the ability to retrieve reports for long periods with any accuracy. The most obvious use-case is in monitoring systems, as it is better to see the picture once, than reading logs hundred times. In the end of this post you can get something similiar to