Monitorix is a free, open source, lightweight system monitoring tool
designed to monitor as many services and system resources as possible.
It has been created to be used under production Linux/UNIX servers, but
due to its simplicity and small size can be used on embedded devices as
well.

It consists mainly of two programs: a collector, called monitorix, which
is a Perl daemon that is started automatically like any other system
service, and a CGI script called monitorix.cgi. Since 3.0 version
Monitorix includes its own HTTP server built in, so you aren't forced to
install a third-party web server to use it.

Note:

There are several runtime dependencies (like pflogsumm) I'm unable to
test for all services. Keep an eye on /var/log/monitorix which will tell
you.