In the preface, we talked about how RRDtool stores data. Now, you'll be looking into the actual graph creation process and what features Cacti supports.

As you have seen in the preface, Cacti uses RRDtool to store the polled data. In addition to just storing the data, RRDtool is also used to create the actual performance graphs.

If you now expect to see a full-featured charting application, you will be disappointed. RRDtool graph functionality only offers a very limited range of chart types. They can either be line charts, area charts, or a combination of both. There is no 3D option available or any other type of chart, such as pie or scatter charts...

A device in Cacti can be anything that can be monitored remotely or locally. This can be a storage device, Windows or Unix servers, and of course network devices. For Cacti to be able to monitor a device it needs to be reachable by ping or SNMP, but the actual data retrieval can also be done using scripts and commands, or a set of SNMP queries. With Cacti 1.0, a new management item has been introduced called Site. The site item allows you to group devices by site and also store site-specific information, such as address, time zone, and GPS coordinates. Before you add a new device, you will therefore first create a site to which you will be assigning the device later.

Site creation...

The Cacti tree lists sub-trees, hosts, and graphs in a tree-like interface. It is the main user interface for the Graphs tab. There can be more than one tree, which allows for a granular definition of the tree structure. Before creating the Cacti tree, think about a good structure for it. Changing the tree later can involve quite a bit of manual work.

With the new 1.0 version of Cacti, the Cacti tree has undergone a major change from the 0.8 version. Previously, the tree management page was built using a static HTML page, which caused a large amount of work when managing large Cacti deployments. Version 1.0 introduced a dynamic JavaScript-based interface with drag-and-drop support, so the tree creation process and, especially, rearranging devices is now a lot easier.

You now have a basic knowledge of the RRDtool graph functionality, and also have your first device added to Cacti.

1. If you want to add an additional threshold line, what do you need to add?
   • A LINE2 item
   • A THRESHOLD item
   • AN HRULE item

2. What information will be displayed when you create an SNMP-enabled device?
   • The hardware configuration of the device
   • A message of the day
   • The contact information and hostname of the device

3. Where do you add the Cisco - CPU Usage graph?
   • On the Cacti tree
   • On the RRDtool command prompt
   • On the device screen

In this chapter, you have learned quite a bit about the RRDtool graph generation features.

Specifically, we have covered how to create some basic graphs using the RRDtool as well as adding advanced features such as threshold lines and color changes based on the threshold. You have briefly covered the concept of adding a device to Cacti and assigning graphs and interface graphs to it. Finally, you have created a new Cacti tree containing sub-tree items and the previously added device.

You now have a running Cacti server, polling and graphing at least one device.

In the next chapter, you will learn how to create your own Cacti templates, where you can directly apply everything you have learned here.