Nscd is a daemon that provides a cache for the most common name service
requests. The default configuration file, /etc/nscd.conf, determines
the behavior of the cache daemon. See nscd.conf(5).
Nscd provides cacheing for accesses of the passwd(5), group(5),
and hosts(5) databases through standard libc interfaces, such as
getpwnam(3), getpwuid(3), getgrnam(3),
getgrgid(3), gethostbyname(3), and others.
There are two caches for each database: a positive one for items found, and a
negative one for items not found. Each cache has a separate TTL (time-to-live)
period for its data. Note that the shadow file is specifically not cached.
getspnam(3) calls remain uncached as a result.
Nscd doesn't know anything about the underlaying protocols for a service. This
also means, that if you change /etc/resolv.conf for DNS queries, nscd
will continue to use the old one if you have configured
/etc/nsswitch.conf to use DNS for host lookups. In such a case, you
need to restart nscd.