Which of the following tools is used for automated configuration management?

The correct choice is focused on tools specifically designed for automated configuration management. Chef, Puppet, and Ansible are popular configuration management frameworks that provide mechanisms to automate the deployment, configuration, and management of systems and applications in a consistent manner across environments.

Chef uses a Ruby-based DSL (Domain Specific Language) to define configurations, allowing for complex automation scripts. Puppet uses a declarative language to define system configurations and can manage both Unix and Windows systems. Ansible, on the other hand, is agentless and uses YAML for its playbooks, making it simple to use and integrate with existing systems.

These tools help in maintaining system integrity and can handle tasks such as package installation, service management, and file handling automatically, which is vital for large-scale infrastructure management. In contrast, Docker is primarily used for containerization, Cron is a time-based job scheduler for running scripts or commands at scheduled times, and OpenStack is a cloud computing platform for managing infrastructure rather than specific configuration management tasks.