posixGroup

posixGroup is an LDAP object class defined by RFC 2307 for representing POSIX-style groups in directory services. It is designed to model the POSIX concept of a group with a numeric group ID and a set of members, enabling UNIX-like systems to retrieve group information from a directory.

Key attributes and structure: The essential attribute for a posixGroup is gidNumber, which stores the group's numeric ID used by the local system. Membership is typically expressed through the memberUid attribute, which lists the user login names. Some schemas (notably RFC 2307bis) also support the member attribute, which references the full distinguished names of user entries. Depending on the directory implementation, other attributes such as cn (common name) or description may be present but are not required by the core specification.

Usage and interoperability: posixGroup is commonly used alongside posixAccount entries to manage UNIX-like users and groups in a centralized directory. Applications and services that rely on POSIX group information can read gidNumber to map to system groups and use user identifiers from memberUid or member to assemble membership data for authentication and authorization.

Considerations: Implementations may vary between directory servers. Some environments prefer memberUid for simplicity, while others use member to link to user DNs. Directory-aware tools for syncing identities (for example, between LDAP and POSIX systems) must align with the chosen schema. Major directory services such as Active Directory do not natively implement RFC 2307 posixGroup, though synchronization solutions exist.

See also: RFC 2307; RFC 2307bis; LDAP; POSIX; group membership.