The NFSv4.1 uses utf8 based strings to represent user and group names. This is the case even for non-kerberos based accesses. Nevertheless UNIX based clients as well as dCache internally use numbers to represent uid and gids. A special service, called idmapd, takes care for principal-id mapping. On the client nodes the file /etc/idmapd.conf is usually responsible for consistent mapping on the client side. On the server side, in case of dCache mapping done through gplazma2. The identity type of plug-in required by id-mapping service. Please refer to Chapter 10, Authorization in dCache for instructions about how to configure gPlazma.

Note, that nfs4 domain on clients must match nfs.domain value in dcache.conf.

To avoid big latencies and avoiding multiple queries for the same information, like ownership of a files in a big directory, the results from gPlazma are cached within NFSv4.1 door. The default values for cache size and life time are good enough for typical installation. Nevertheless they can be overriden in dcache.conf or layoutfile:

..
# maximal number of entries in the cache
nfs.idmap.cache.size = 512

# cache entry maximal lifetime
nfs.idmap.cache.timeout = 30

# time unit used for timeout. Valid values are:
# SECONDS, MINUTES, HOURS and DAYS
nfs.idmap.cache.timeout.unit = SECONDS
..