What command will terminate all instances of a specific process name?

The command that effectively terminates all instances of a specific process by its name is "killall process_name." This command is specifically designed to send signals to all processes running with the specified name. When you use "killall," it scans the currently running processes and sends the specified signal (with the default being the TERM signal) to any process that matches the provided name. This utility is straightforward and efficient for managing multiple instances of the same process simultaneously.

In contrast, the other options do not serve the same function. A command like "kill process_name" is generally incomplete because "kill" typically requires a process ID (PID) rather than the name of the process. The command "terminate process_name" does not exist in standard Linux commands and would result in an error if attempted. Similarly, "stopall process_name" is not a valid command in Linux, as there is no built-in command called "stopall" for process management. Thus, "killall process_name" is the correct choice for terminating all instances of a process effectively.