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GNU cfengine

3.4 Defining classes and making exceptions

Cfengine communicates with itself by passing messages in the form of classes. When a class becomes switched on or off, cfengine's program effectively becomes modified. There are several ways in which you can switch on and off classes. Learning these fully will take some time, and only then will you harness the full power of cfengine.

• Classes may be defined manually from the command line.

• Classes may be defined locally in the actionsequence in order to execute only some of the actions within a special category.

• Classes may become defined if cfengine actually needs to carry out an action to repair the system's configuration.

• Classes may be defined by user-defined plug-in modules.

Because cfagent works at a very high level, doing very many things for very few lines of code it might seem that some flexibility is lost. When we restrict certain actions to special classes it is occasionally useful to be able to switch off classes temporarily so as to cancel the special actions.

3.4.1 Command line classes
3.4.2 actionsequence classes
3.4.3 shellcommand classes
3.4.4 Feedback classes
3.4.5 Writing plugin modules