Which command will allow the atd service to start at boot if it is not already configured that way?

The command that allows the atd service to start at boot is correctly identified. Using sudo systemctl enable atd performs the function of configuring the system to automatically start the atd service during the boot process.

When the enable command is executed with systemctl, it sets up the necessary symlinks in the default target directory (usually /etc/systemd/system/multi-user.target.wants/) to ensure that the service starts up when the system reaches the specified run level or target. This is an essential part of managing services in a modern Linux environment that uses systemd for service management.

In contrast, the other options involve either incorrect syntax or commands that do not serve the purpose of enabling a service at boot. For example, disabling a service or using a nonexistent command will not achieve the goal of ensuring that the atd service starts automatically when the system boots. Understanding the structure and usage of systemd commands is crucial for effective system administration in RHEL Linux.