SUMMARY: nscd (Name Server Cache Daemon)

From: Richard Pieri (
Date: Thu Apr 25 1996 - 13:59:26 CDT


I received one somewhat hesitant response which contained nothing that I
had not already garnered from the sparse man pages. ncsd, Name Server
Cache Daemon, caches passwd, group, and hosts lookups, including network
lookups (DNS, NIS/NIS+).

Since then we have stumbled onto a "problem", the problem with any
cached data: when new zone data is loaded into the nameserver, the data
in the nscd cache will be rendered obsolete. This data is not
automatically purged/updated when bind loads a zone.


* Do not run nscd (remove the startup script from /etc/rc2.d)

  This is best for machines running nameservers and are also NIS/NIS+
  masters or slaves, as the servers are already caching the same data
  nscd would. Also good for nameservers and clients that are not using
  NIS/NIS+ and are connected by a fast, unloaded network.

* Every time zone data is loaded, kill all nscds and restart at the end
  of the load, or render the cache data invalid with 'nscd -i hosts'.

  This is probably not practical for anything other than the smallest of

* Disable nscd's hosts caching, allowing bind to do that alone (edit
  /etc/nscd.conf, add a line that reads 'enable-cache hosts no'; by
  default such a line is there and simply needs to be uncommented).

  A good choice for nameservers that are getting NIS/NIS+ data from
  other servers.

* Leave nscd running with full caching enabled, and cope with the
  10-minute TTL for cached data (default TTL can be modified in

  What you have left if the first three options simply will not do. You
  may or may not wish to disable parts of the nscd cache that you feel
  should always be retrieved from the appropriate server(s), or are
  simply not necessary for your particular setup.

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