What configuration file is responsible for controlling user login settings in Linux?

The configuration file that controls user login settings in Linux is /etc/login.defs. This file contains a variety of parameters that dictate the behavior of the system regarding user accounts and login settings. Specifically, it defines the default settings for user accounts, including password expiration time, user ID ranges, and other security-related options.

For instance, within /etc/login.defs, administrators can configure settings such as the maximum number of days a password can be valid, what happens when a password expires, and password creation settings. These configurations help maintain security and manage user authentication effectively.

The other files listed serve different purposes: /etc/profile is a script that sets up the environment for users when they log in, and it is used for global settings affecting all users in their shell environment. /etc/passwd contains basic user account information such as usernames, user IDs, and shell paths but does not control login behavior directly. Finally, /etc/user.conf is not a standard configuration file in most Linux systems and does not typically control login settings. Thus, /etc/login.defs is the correct file for managing user login configurations.