Windows users and groups are defined in a Security Account Manager (SAM) database, which is managed on a Windows domain controller. Each user and group is identified by a security identifier (SID). An SID is a variable-length structure that uniquely identifies a user or group both within a host and a local domain, and across all possible Windows domains.
The text form of an SID is represented as follows:
S – Identifies the string as an SID.
SA – Is one or more subauthorities, such as a relative identifier (RID).
In a domain SID, the RIDs identify the domain. In a user or group SID, except for the last RID, the RIDs identify the machine or the domain that issues the SID. The last RID identifies the user or group.
For example, the S-1-5-32-500 SID contains a version number of 1. The identifier authority value is 5, and it contains the 32 and 500 subauthorities. The value 500 is the RID.
The idmapd service generates a unique SID for the host on which it runs. This SID is used to represent both users and groups that cannot be mapped by name to SIDs. This SID is stored in the equivalent of a local SAM database. The Solaris computer SID is generated randomly.
The idmap service generates a unique SID, machine-SID, for the host on which it runs. This SID is used to generate local SIDs as follows:
local SID for user = machine-SID - 1000 + user's-UID local SID for group = machine-SID - 2^31 + group's-GID
For instance, the local SID for a user with a UID of 182048 and a machine SID of S-1-5-21-726303253-4128413635 is S-1-5-21-726303253-4128413635-183048.
Local SIDs are used to represent Solaris users or groups that have non-ephemeral UIDs or GIDs and that cannot be mapped by name.