Solaris users and groups can be defined in local files (/etc/passwd and /etc/group) or in a naming or directory service, such as NIS and LDAP. The naming services you configure are listed in the Solaris naming services switch file /etc/nsswitch.conf. For more information, see Chapter 2, The Name Service Switch (Overview), in System Administration Guide: Naming and Directory Services (DNS, NIS, and LDAP).
The Solaris CIFS service can be configured as a client of the various distributed naming services, such as NIS and LDAP. For information about configuring the Solaris CIFS service as a client for these naming services, see System Administration Guide: Naming and Directory Services (DNS, NIS, and LDAP).
Each user and group is assigned a 32-bit identifier known, respectively, as a user ID (UID) and a group ID (GID). The Solaris OS has extended the uid_t and gid_t types from signed to unsigned 32-bit integers. Now that the uid_t and gid_t types are unsigned, the upper half of these namespaces is available for ephemeral dynamic ID mapping. This mapping process enable IDs to be assigned dynamically and ephemerally on demand. An ephemeral mapping is one that does not survive a Solaris system reboot. Typically, the UID or GID uniquely identifies a user or group within a single Solaris domain. However, these values are not unique across domains.
Traditionally, UID 0 or GID 0 is assigned to the root user or group. The root user is granted almost unlimited access to system objects in order to perform administration tasks.