What is the function of the /etc/shadow file?

The /etc/shadow file serves a critical role in Linux systems by storing encrypted user passwords. This file is designed to protect sensitive information, specifically the hashed passwords of users. Unlike the /etc/passwd file, which contains user account details such as usernames and user IDs, the /etc/shadow file restricts access to this data and is generally only readable by the root user and some privileged processes.

The hashing process used for passwords ensures that even if an unauthorized party gains access to the /etc/shadow file, they cannot easily retrieve the original plaintext passwords. This enhances system security by making it much more difficult for attackers to compromise user accounts.

Additionally, the /etc/shadow file may also include other information related to passwords, such as password expiration and account expiration details, further contributing to the management of user authentication and security policies.