To display detailed information about currently active services, which command is appropriate?

The command that displays detailed information about currently active services is systemctl list-unit-files --type=service. This command interacts with the systemd system and service manager, which is responsible for initializing and managing services on many Linux distributions, including those based on Red Hat.

When you use systemctl with the list-unit-files option along with the --type=service flag, it specifically lists all service units, giving you a snapshot of each service's state (enabled, disabled, static, or masked). This is particularly useful for system administrators looking to understand which services are currently activated, their configuration status, and any dependencies they may have.

In contrast, the other options listed have different functions. The swapon -s command is used for displaying swap space information. The mount -a command mounts all filesystems mentioned in fstab except for those marked with the noauto option, which is related to file system management rather than service status. Lastly, fdisk is a tool for partitioning disks and does not provide information about services at all. Thus, the correct choice effectively addresses the need to monitor active services in a Red Hat environment.