Graph Any Data with Cacti!

Part III: Data Sources

Now that you have the Data Input Method and a Data Template to tell Cacti how to use it, you need to create your two data sources. Head over to "Data Sources" on the left, and then click "Add" in the upper right in order to add your first source. The first page asks you to select a Data Template and Host. This data source isn't related to a specific server, so leave Host as "none", but you want to select your freshly created Data Template (Figure 12) and click Create.

Figure 12. Cool, the data template!

Since the Data Template already answers most of the questions about the new data source, you're asked only a few details. In Figure 13, you can see that I need to name this data source, choose a data source path and give it the weather station code. I just used the default Data Source Path that Cacti created. Once you enter the name and weather station code, click Save.

Figure 13. See? It's much easier to create a data source when you have only two things to enter!

If you're following along and want to do something similar to me, repeat the process for your second weather station. Since the Data Template is already in place, adding a second Data Source is very simple. I added Houston exactly the same way as I added Petoskey.

Part IV: the Graphs

Creating the Data Sources is really the hardest part of creating graphs with Cacti. Once they're created, the data will be polled every five minutes, and data will be added to the RRD files. You can't create a graph until you have a Data Source created, because graphs simply show the data inside the Data Sources graphically. So, now that you have Data Sources, you can create graphs to display them.

It's possible to set up Graph Templates, but unlike Data Templates, they're not really required. In my case, since I created only one graph, it would take longer to set up a template than simply to create a graph from scratch, so I'll just do it from scratch. In order to start, click on "Manage Graphs" on the left-hand side of the screen. (Note: don't click "New Graphs", because for some reason, Cacti will try to use a host and not give you the option for selecting a Data Source that doesn't have an associated host. Thankfully that isn't a problem in the "Graph Management" section.)

Once in Graph Management, click "Add" in the upper-right corner. Select "None" for both host and template (Figure 14), because you're not going to use a template for this graph. Then click Create.

Figure 14. Graph Templates won't save you any time, but if you're doing lots of similar graphs, check them out.

The next page (Figure 15) looks overwhelming, but you're going to leave almost everything at its default. The only things I added were the Title of the graph (Petoskey & Houston) and, at the bottom, the Vertical Label (degrees Fahrenheit). For your first graph, I recommend leaving everything else at its default. Click Create.

Figure 15. Thankfully, you want mostly all defaults.

The next page (Figure 16) looks similar, but notice the section I circled in red titled "Graph Items". You need to click "Add" on the right in that section, and add the Data Sources. You'll see I chose "Houston Temperature" as the Data Source to graph (Figure 17).

Figure 16. I missed this section at first and was confused why I didn't get any graphs.

Figure 17. Why on earth does the drop-down box show only HEX?

______________________

Shawn Powers is a Linux Journal Associate Editor. You might find him on IRC, Twitter, or training IT pros at CBT Nuggets.