Did you know CFEngine can self-organize hosts into different groups? Say you have a few hosts that you want to reboot once a month. You don’t care when, but you want the hosts to self-organize and pick a date. The select_class attribute for classes type promises might be what you’re …
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 …
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 …
Ever need to visualize the data you’re working with? storejson() to the rescue! Let’s re-visit our example for sys.os_release from Feature Friday #12: Special variables: bundle agent __main__ { reports: "My custom key 'NORTHERN_TECH_OWNER' contains …
Did you know you can use variables in class expressions? If you are reading this, you probably are already familiar with the ability to use class expressions to restrict the context of multiple promises. For example, here we have three reports type promises, all guarded by the class expression …
Class expressions are powerful. They let you restrict the context for multiple promises in a single statement. What if you want to further control the context of a specific promise? Let’s take a look at a contrived example: /tmp/feature-friday-28-0.cf bundle agent __main__ { reports: "I am …
When promises are actuated, a class can be defined based on its result. For example, if a promise modifies a file’s content, you could define a class that indicates it has been repaired. However, did you know that promises can have multiple outcomes concurrently? That’s right! Native …
There’s a users promise type for managing local users. However, did you know there is also a custom one for managing local groups? You might have seen it mentioned in the CFEngine Build announcement, the blog post on Managing local groups, or in the announcement supporting custom bodies post. …
Generally, cf-agent runs as a privileged user. But did you know that you can also run as an unprivileged user? A major benefit of running cf-agent unprivileged is the ability to prototype policies during development. However, attempting to execute cf-agent as an unprivileged user without proper …
You probably know about the def.json Augments file. However, are you familiar with host_specific.json? The def.json Augments file is read, if it’s adjacent to the policy entry. As such, this file is generally distributed as part of the policy set. Its settings apply to all hosts that receive …
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