Idmapdconf

Idmapdconf refers to the configuration file for the idmapd daemon, the identity mapping service used by NFSv4 to translate between local UNIX user/group IDs and the identities seen by remote clients. The file is typically located at /etc/idmapd.conf and is read by the idmapd service when it starts. It defines how identity mapping is performed across hosts in an NFSv4 environment, enabling consistent access control for files exported over NFS.

The configuration is organized into sections, commonly including [General] and [Mapping]. In [General], Domain specifies the NFSv4 identity domain used for mapping and may include logging-related options such as Verbosity. The Domain setting should be consistent across clients and servers that share the same NFSv4 realm. The [Mapping] section defines how unmapped identities are handled, for example by specifying Nobody-User and Nobody-Group, and may include other mapping-related directives that influence how names are translated to UIDs and GIDs.

Operationally, idmapd uses the directives in idmapd.conf to translate user and group names exchanged during NFSv4 operations into the numeric IDs used by the local filesystem, and vice versa. If a name cannot be mapped, the configured nobody accounts are used as a fallback. The exact directives and syntax can vary between distributions, so system-specific documentation should be consulted.

After editing idmapd.conf, the idmapd service typically needs to be restarted for changes to take effect, using commands such as systemctl restart nfs-idmapd or, on older systems, service idmapd restart. A properly configured idmapd is essential for correct access control across NFSv4 clients, especially in environments using LDAP or Active Directory for identity information.