Which Unix password files commonly store password hashes that authentication relies on?

• A. Both /etc/passwd and /etc/shadow
• B. /etc/passwd
• C. /etc/shadow
• D. /etc/hosts

Answer: (A)

Password verification on Unix systems relies on the stored password hash. In modern setups, the real hash and related aging data live in /etc/shadow, which is protected so only privileged processes can read it. The corresponding user account information—such as username, UID, shell, home directory—lives in /etc/passwd. On systems using shadow passwords, the password field in /etc/passwd contains a placeholder (often an x) rather than the actual hash, signaling that the hash is kept in /etc/shadow. Some older or non-shadow configurations may still store the hash in /etc/passwd. Since authentication checks the stored hash, both files are part of the password database, while /etc/hosts is unrelated to authentication.