Why Are User Passwords Stored in /etc/shadow Instead of /etc/passwd?

Why Are User Passwords Stored in /etc/shadow Instead of /etc/passwd?

When it comes to managing user accounts on a Unix-based system, the location where user passwords are stored plays a crucial role in maintaining security. In Unix-based systems, such as Linux, user passwords are typically stored in a protected file called /etc/shadow rather than the more commonly known /etc/passwd. This decision is made for security reasons.

The /etc/passwd file traditionally stored user account information, including usernames, user IDs, group IDs, home directories, and shell access. However, it also used to store encrypted passwords in the past, which posed a security risk. If an attacker gained access to the /etc/passwd file, they could potentially decrypt the passwords using techniques like brute force or rainbow tables.

To address this security flaw, the /etc/shadow file was introduced. The /etc/shadow file is readable only by the root user, making it more secure than the /etc/passwd file. It stores user password hashes, which are encrypted representations of passwords that are extremely difficult to reverse engineer.

By moving the storage of passwords to the /etc/shadow file, Unix-based systems enhance the overall security posture by preventing unauthorized access to user passwords. This segregation of sensitive information helps mitigate the risk of password exposure in case of a system breach.

In conclusion, the decision to store user passwords in /etc/shadow instead of /etc/passwd is a security measure aimed at protecting sensitive user authentication data from malicious actors.