Home > Storage > PowerScale (Isilon) > Product Documentation > Management and Migration > PowerScale OneFS User Mapping: Mapping Identities Across Authentication Providers > User mapping introduction
User mapping provides a way to control access by specifying a user’s complete list of security identifiers, user identifiers, and group identifiers. OneFS uses the identifiers— which are commonly called SIDs, UIDs, and GIDs respectively—to determine ownership and check access.
With the user mapping service, rules are configured to manipulate a user’s access token by modifying which identity OneFS uses, adding supplemental user identities, and changing a user’s group membership. OneFS maps users only during login or protocol access.