I enjoy watching monitors. Here are some notes about what works and what doesn't. I suppose some of you know about other useful software which you can point out to me.

Forget the Gnome panel monitors. None of them work well. Get gkrellm. It shows separate meters for the two cores on my Athlon mb and reads 5 temperature sensors (while the Gnome panel sensors could only read one). Shows lots of other stuff, also, but it does take up some screen real estate.

I got hddtemp, a daemon which tracks hard disk temperatures, as an Fedora Core 6 package, and didn't at first realize that you have to edit a script, /etc/sysconfig/hddtemp, to specify what disks you want monitored. That done, it works fine on my system, and Gkrellm displays the temperatures it reads.

I installed Nagios several years ago on a server I administer at work, and there's a companion extension for Firefox which queries Nagios over the web to check on the server's health. As I browse, I can see a nice reassuring green "No problem" notice if the server is ok, but it turns red and buzzes at me if something goes wrong. Neat. (I think I could set up a remote Gkrellm monitor for the server, too, but I haven't yet tried that.)

We use Nagios for enterprise monitoring. There are NRPE plugins for UNIX/Linux of various flavors as well as NSCLIENT for Windoze not to mention so stray plugins I've found such as one for AS400.

Given that we have over 50 UNIX/Linux systems and God knows how many Windoze servers having a central web page such as that provided by Nagios is great.

whilst npre is cool, from what i'm aware, nagios as a whole seemed pretty poor. it handles snmp very badly when i tried to use it and really doesn't scale at all well. anyone monitoring more than a few dozen servers and needing things like autodiscovery and such would be much better of using somethign like opennms (which also supports npre) or the more shiny commercially backed groundwork, zenoss etc...

Well if you're doing more than just snmp Nagios is a good way to go as it allows for customizations. As noted we're doing 50+ UNIX/Linux systems and many more Windoze systems without any issues.

Some of the pay for products may have more bells and whistles but I thought we were talking about the free stuff here.

Patrol is the one I used most in pay for arena (at more than one job) - it was fully customizable as well and after BMC bought Best/1 and reengineered the data collection it became a much better product.

everything i mentioned about is free, at least for a cut down version which i *think* will still always do more than nagios.