collectd, the system statistics collection daemon

collectd is a small daemon which collects system performance statistics periodically and provides mechanisms to store the values in a variety of ways, for example in RRD-files.

What does collectd do?
collectd gathers information about the system it is running on and stores this information. The information can then be used to find current performance bottlenecks (i. e. performance analysis) and predict future system load (i. e. capacity planning). Or if you just want pretty graphs of your private server and are fed up with some homegrown solution you're at the right place, too ;).

While collectd can do a lot for you and your administrative needs, there are limits to what it does:

• It does not generate graphs. It can write to RRD-files, but it cannot generate graphs from these files. There's a tiny sample script included in contrib/, though. Also you can have a look at drraw for a generic solution to generate graphs from RRD-files.
• Monitoring functionality has been added in version 4.3, but is so far limited to simple threshold checking. The document "Notifications and thresholds" describes collectd's monitoring concept and has some details on the limitations, too. Also, there's a plugin for Nagios, so it can use the values collected by collectd.