How does modifying users work internally in Linux?

In Linux, managing user accounts involves a set of processes that modify user attributes such as usernames, passwords, privileges, and groups. These modifications are typically done using command-line tools such as useradd, usermod, and userdel. User account information is stored in system files, primarily /etc/passwd for user details, and /etc/shadow for password information.

To modify a user, the usermod command is commonly used, allowing administrators to change user settings such as user home directory, password expiration, and user groups.

For example, to change a user's home directory, you might use: