event2vrule(1) on Linux
The text e40cd8ead6b2, as Debian 10 (Buster), Debian 9 (Stretch), Debian 8 (Jessie), Debian 7 (Wheezy), Debian 6.0 (Squeeze), Debian 5.0 (Lenny), Debian 4.0 (Etch), Debian 3.1 (Sarge) shipped it. The page shows this text now.
adds 'events' to rrdtool graphs