How does Samba manage to authenticate using different password backends?

Samba's ability to authenticate using different password backends primarily comes from its integration with various authentication systems. This flexibility allows Samba to not only manage its own user accounts but also work seamlessly with existing user databases, such as those found in Active Directory (AD), LDAP directories, and traditional UNIX/Linux systems.

By supporting multiple authentication methods, Samba can effectively bridge the gap between different network operating systems, allowing users to authenticate using credentials stored in systems that might differ in architecture. This means that administrators can configure Samba to validate user credentials against these diverse backends without needing to restrict the system to a single storage method.

The other options fail to capture the essence of Samba's capabilities. For instance, while a common UNIX password policy might be relevant for some cases, it does not encompass the various integrations Samba supports. Similarly, restricting to only its own password storage or requiring manual entry for each user password would severely limit functionality and usability, which contradicts the purpose of Samba as a versatile file and print server in mixed environments.