What command can help in determining if a service is active in the system?

The command systemctl status is the correct choice for determining if a service is active in the system, especially on systems using Systemd, which is the init system for many modern Linux distributions. When this command is executed, it provides detailed information about the specified service, including its current status (active, inactive, or failed), recent logs related to the service, and other relevant metadata.

Using systemctl status allows users to quickly and effectively check whether a service is running and to view any issues that may have occurred recently, which is essential for system administration and troubleshooting.

In contrast, the other choices do not provide the same level of detail or are limited in their applicability. The service status command may be applicable on some older distributions but lacks the comprehensive output that systemctl provides. The chkconfig command is geared towards managing system services as runlevels rather than checking current statuses, and ps aux lists currently running processes without a direct focus on the status of services controlled by init systems. Thus, for a clear and comprehensive understanding of service status in a modern Linux environment, systemctl status is the optimal choice.