Which directive in smb.conf must be configured for Samba to act as a Domain Master Browser?

To configure Samba to act as a Domain Master Browser, the directive that needs to be set in the smb.conf file is "domain master." This directive tells Samba that it should participate in master browser elections, enabling it to take on the role of the Domain Master Browser, which helps maintain a list of all active servers within a given workgroup or domain. The Domain Master Browser centralizes the browsing information for the domain, ensuring that workstations can see all available resources on the network effectively.

The function of this directive is crucial in mixed-network environments where there may be multiple browsers operating, as it prevents fragmentation of the browsing data. By designating a specific Samba server as the Domain Master Browser, the network maintains a cohesive view of shared resources, making it easier for users to access these resources from their clients.

The other choices pertain to different functionalities within Samba. For instance, "domain logons" allows Samba to manage user logins, "logon script" specifies the script that runs at user login, and "security" sets the security mode for Samba, but none of these would enable the server to function as a Domain Master Browser.