Which utility is primarily used for configuring TCP/IP settings on Linux and UNIX systems?

The utility primarily used for configuring TCP/IP settings on Linux and UNIX systems is indeed ifconfig. This command allows users to view and modify the network interface configurations on a system. By using ifconfig, administrators can assign an IP address to a network interface, enable or disable the interface, and show the current configuration and status of network interfaces.

It is particularly important for managing older network configurations, and although it has been largely replaced in many distributions by the ip command for more advanced functionality, ifconfig remains a fundamental tool and is still present in many systems for compatibility reasons.

The other choices involve network management as well but serve different specific purposes. For instance, ip address show displays the routing table and current network configurations in a more detailed manner, while route is primarily used for managing the routing tables. The whoami command, on the other hand, is used to display the effective username of the current user, making it unrelated to network configuration tasks.