What is the open-source equivalent of Active Directory in Linux?

The open-source equivalent of Active Directory in Linux is LDAP, which stands for Lightweight Directory Access Protocol. LDAP is a protocol used to access and manage directory information services over a network. In many Linux environments, LDAP is utilized to store and manage user accounts, authentication, and organizational relationships similarly to how Active Directory operates in Windows environments.

By using LDAP, organizations can maintain a centralized user directory that supports various network services, allowing for seamless authentication and authorization across Linux systems. This makes it a foundational component for identity management in Linux, paralleling the capabilities provided by Active Directory in Windows systems.

While Kerberos is an authentication protocol that can be integrated with LDAP to secure communication and verify user identities, it does not provide the comprehensive directory services that LDAP itself offers. Samba is typically used to provide file services and can facilitate Active Directory interoperability, but it does not function as a directory service on its own like LDAP does. OpenID is a decentralized authentication protocol primarily used for web-based applications, which is not directly related to directory services in an operating system context.

Therefore, LDAP stands out as the correct answer because of its primary role in managing directory information and user accounts in a Linux environment, making it the equivalent of Active Directory in that setting.