The Unix "su" command fundamentally changed how users access systems. Originally designed as a simple tool to switch between user accounts, su gradually replaced the traditional "login" command for certain administrative functions. This shift represented a significant evolution in Unix system administration practices, simplifying the workflow for privileged operations while maintaining security boundaries.

This transition reflected broader Unix design philosophy of composability and modularity. Rather than requiring separate login processes, administrators could now leverage existing user sessions with elevated privileges. The su approach reduced overhead and created more efficient workflows while preserving the principle of least privilege through controlled privilege escalation mechanisms.

The evolution from login to su demonstrates how Unix systems prioritize flexibility and efficiency. This seemingly minor change actually reshaped system administration practices across Unix derivatives. The su command's endurance in Unix systems for decades stands as testament to its effective design and the lasting impact of this administrative paradigm shift.