What’s the difference between an associative array and a data container in CFEngine? CFEngine has two ways in which structured data can be used, associative arrays (sometimes called classic arrays) and data containers. Let’s take a look at a simple data structure. Here we have two data structures, a_email an associative array and d_email a data container. The policy emits the JSON representation of each.

Ever need to do some math during policy evaluation? Sometimes configuration settings are based on available resources. For example, what if you want to calculate the size of shared buffers to be 25% of your available memory? Let’s write some policy. First, we need to figure out how much memory we have. Let’s parse this out from /proc/meminfo: So, we have 65505464 kB of memory in total. Knowing that we can use eval() to calculate what 25% is. eval() can also be used to test truthfulness.

Within the configuration management space, people often distinguish between agent-based and agent-less approaches. In short, an agent-based solution means that you install a software agent to run in the background / periodically on the system. That software agent then makes changes to the system as desired, and also commonly communicates over the network to send and receive updates, policy, commands, scripts, data, etc.

Ever need to visualize the data your working with? storejson() to the rescue! Let’s re-visit our example for sys.os_release from Feature Friday: Special variables: So, we saw the value of a single key, but if we don’t know what keys are available it can be useful to render the JSON representation. The with attribute in combination with storejson() provides a convenient way to visualize the JSON representation of structured data in CFEngine.

I promised more Build modules in my previous monthly Monday module blog post: package-method-winget. And here they are: windows-capability and windows-optional-feature.

Ever want a custom CFEngine Agent logo? Check out agentsvg. You can find agentsvg in core/contrib/ it’s a python script that can generate CFEngine agent logos. In addition to customizing the head and body colors you can customize the arm positions to be up, down, out or angled and the legs can be straight or out Happy Friday!