There are several programs for monitoring your server. All of these programs are powerful and extensive. But they are also quite heavy and consume a lot of resources. That does not affect big servers but may slow down smaller/embedded devices like a Raspberry Pi.
That’s why I wrote a little bash script and a R-Markdown file to give a few information about the current state of my Pi (used for DHCP, DNS, printer server, WINS server). The bash script collects relevant data (load, temperature, memory consumption, network traffic) and stores it in a sqlite database. R and knitr load the data, do some data management and produce a few nice ggplot2 graphics. The output is a simple HTML-File with encoded graphics which also allows to send one single file via email.
There is a sample showing daily and weekly graphs. The file is generated once a day which can of course be changed.
The code is available at github and licensed under the MIT License. So feel free to use/change/extend it.