Manpages - nscd.8

nscd - name service cache daemon

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 caching for accesses of the *passwd*(5), *group*(5), *hosts*(5) *services*(5) and netgroup 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.

–help

will give you a list with all options and what they do.

The daemon will try to watch for changes in configuration files appropriate for each database (e.g., /etc/passwd for the passwd database or /etc/hosts and /etc/resolv.conf for the hosts database), and flush the cache when these are changed. However, this will happen only after a short delay (unless the *inotify*(7) mechanism is available and glibc 2.9 or later is available), and this auto-detection does not cover configuration files required by nonstandard NSS modules, if any are specified in /etc/nsswitch.conf. In that case, you need to run the following command after changing the configuration file of the database so that nscd invalidates its cache:

  $ nscd -i <database>

*nscd.conf*(5), *nsswitch.conf*(5)

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