The primary goal of hardening a computer system's operating system is to reduce its attack surface by eliminating unnecessary functions, services, and installations that could be exploited by an attacker. By securing the system configuration, the overall security posture is improved, making it more difficult for malicious actors to find and exploit vulnerabilities. Securing configurations may include implementing the principle of least privilege, disabling unnecessary ports, services, and daemons, and using security controls tailored to the function of the system. Other answers may seem related, such as creating backups or improving the user interface, but they do not directly correspond to the primary goal of system hardening, which is to reduce vulnerabilities.