If you're a system or network administrator, you need to know the status of your systems so you can optimize performance and head off potential problems. Thankfully, plenty of tools are available to help you stay vigilant.
Here are five free system and/or network monitors that do as much or more than the pricier solutions.
Note: If you'd prefer to view this information as a blog post, check out this entry in our Five Apps blog.
Observium offers detailed graphs and an easy-to-use interface. It can monitor a huge number of processes and systems. The only downside is a lack of auto alerts, but you can set up Observium alongside a tool like Nagios for up/down alerts.
Ganglia is a "scalable distributed monitoring system" focused on clusters and grids. It gives you a quick and easy-to-read overview of your entire clustered system. This monitor has been ported to many platforms and is used on thousands of clusters around the world.
Anyone who employs server clusters should have Ganglia monitoring that system. Ganglia can scale to handle clusters with as many as 2,000 nodes.
Spiceworks one of the industry standard free network/system monitoring tools. You have to put up with some ads, but the features and Web-based interface are topnotch. Spiceworks monitors and autodiscovers your systems, alerts you if something is down, and provides excellent topographical tools.
Spiceworks also lets you get social with fellow IT pros via the Spiceworks community, which is built right in.
Nagios isn't the easiest tool to set up and configure (you have to manually edit configuration files), but it's incredibly powerful. And the manual configuration actually makes Nagios one of the most flexible network monitors around.
Nagios includes a vast number of features. You can even set up email, SMS, and printed paper alerts!
Zabbix is a powerful network monitoring tool that offers user-defined views, zooming, and mapping on its Web-based console. It also offers agent-less monitoring, collects nearly ANY kind of data you want to monitor, does availability and SLA reporting, and can monitor up to 10,000 devices.
One unique Zabbix feature is the option to set audible alerts. If something goes down, you can have Zabbix play a sound file (say, a Star Trek red alert klaxon?).