Ganglia is a scalable distributed monitoring system for high-performance computing systems such as clusters and grids. It is based on a hierarchical design targeted at federations of clusters. Ganglia is currently in use on over 500 clusters around the world and has scaled to handle clusters with 2000 nodes.
Modem.pl is a small script that scrapes the Web interface of a Motorola SURFboard cable modem for various status conditions like signal strength and signal to noise ratio. The results are sent to STDOUT where they can be easily piped into a log file. The modem values are also checked for reasonable operating ranges. If the modem values are outside of reasonable operating ranges, results are also sent to STDERR. When run from a cron job, modem.pl can be used to monitor the condition of the cable service and notify someone before conditions cause service interruptions.
BigDaddy is a program for monitoring servers. It is similar to Nagios, with the added benefit of also monitoring and controlling the crontab (or any scheduled application) across an entire fleet of servers. The application comes in the form of a daemon for monitoring and reporting as well as an easy-to-use Web-based GUI for controlling monitoring, viewing timelines of incidents, filing incidents and graphing statistics. The application is extensible with any sort of monitoring module and notification is based on a five step escalation process.
simena-io is a Linux tool written in Perl and designed to show ethernet interface statistics in bits/second and packets/second in real time. It requires at least Linux kernel 2.2 and Perl 5. It does not require a root account. There is only one command parameter: the refresh rate in seconds. If no parameter is provided, simena-io will refresh every 2 seconds by default. Detailed documentation can be obtained by running "perldoc simena-io".