Monitorix
From James's Wiki
how to install on RPI
sudo apt-get install rrdtool perl libwww-perl libmailtools-perl libmime-lite-perl librrds-perl libdbi-perl libxml-simple-perl libhttp-server-simple-perl libconfig-general-perl libio-socket-ssl-perl
wget "http://www.monitorix.org/monitorix_3.10.0-izzy1_all.deb"
sudo dpkg -i monitorix_3.10.0-izzy1_all.deb
this next step was not necessary last time I installed
sudo apt --fix-broken install
http://localhost:8080/monitorix/
edit the config file:
sudo nano /etc/monitorix/monitorix.conf
restart after editing config:
sudo systemctl restart monitorix