Configuration management

Configuration management tools help to configure OS settings, such as creating a user or group, or installing system libraries. It also acts as an orchestrator, which keeps multiple managed servers consistent with our desired state. 

It's not a programming script, because a script is not necessarily idempotent. This means that if we execute a script twice, we might get an error, such as if we are trying to create the same user twice. Configuration management tools, however, watch the state, so if a user is created already, a configuration management tool wouldn't do anything. If we delete a user accidentally or even intentionally, the configuration management tool would create the user again.

Configuration management tools also support the deployment or installation of software to the server. We simply describe what kind of software package we need to install, then the configuration management tool will trigger the appropriate command to install the software package accordingly.

As well as this, if you tell a configuration management tool to stop your application, to download and replace it with a new package (if applicable), and restart the application, it'll always be up-to-date with the latest software version. Via the configuration management tool, you can also perform blue-green deployments easily.