Which line should be added to smb.conf to avoid UID and GID inconsistencies across servers over SMB?

`ldap dn` is not a valid `smb.conf` parameter for configuring the ID mapping backend; it's typically used for specifying a Distinguished Name.

`ldap server = ldap://ldapserver.com` configures the LDAP server for general use but does not specifically define the `idmap` backend for UID/GID consistency.

`idmap backend = idmap_rid:BUILTIN=ldapserver.com` uses the `idmap_rid` backend, but the format provided is incorrect for centralizing via LDAP, as `idmap_rid` relies on a domain SID for mapping, not a direct LDAP server URL in this manner.

Setting `idmap backend = ldap:ldap://ldapserver.com` configures Samba to use a centralized LDAP directory as the authoritative source for mapping SIDs to UIDs and GIDs. This ensures that all Samba servers referencing the same LDAP server will assign consistent UIDs and GIDs, thus avoiding inconsistencies across servers.

`ldap passwd sync` is a parameter for synchronizing passwords between Samba and LDAP, not for ensuring consistent UID/GID mapping across multiple servers.