nscd is a process that provides a cache for the most common name service requests. It starts up during multi-user boot. The default configuration-file /etc/nscd.conf determines the behavior of the cache daemon. See nscd.conf(4).

nscd provides caching for the passwd(4), group(4), hosts(4), ipnodes(4), exec_attr(4), prof_attr(4), and user_attr(4) databases through standard libc interfaces, such as gethostbyname(3NSL), getipnodebyname(3SOCKET), gethostbyaddr(3NSL), and others. Each cache has a separate time-to-live for its data; modifying the local database (/etc/hosts, /etc/resolv.conf, and so forth) causes that cache to become invalidated upon the next call to nscd. The shadow file is specifically not cached. getspnam(3C) calls remain uncached as a result.

nscd also acts as its own administration tool. If an instance of nscd is already running, commands are passed to the running version transparently.

In order to preserve NIS+ security, the startup script for nscd (/etc/init.d/nscd) checks the permissions on the passwd table if NIS+ is being used. If this table cannot be read by unauthenticated users, then nscd will make sure that any encrypted password information returned from the NIS+ server is supplied only to the owner of that password.

Several of the options described below require a cachename specification. Supported values are passwd, group, hosts, ipnodes, exec_attr, prof_attr, and user_attr.

-f configuration-file

Causes nscd to read its configuration data from the specified file.

-g

Prints current configuration and statistics to standard output. This is the only option executable by non-root users.

-e cachename, yes|no

Enables or disables the specified cache.

-i cachename

Invalidate the specified cache.

/etc/nscd.conf determines athe behavior of the cache daemon

See attributes(5) for descriptions of the following attributes:

getspnam(3C), gethostbyname(3NSL), getipnodebyname(3SOCKET), exec_attr(4), group(4), hosts(4), ipnodes(4), nscd.conf(4), nsswitch.conf(4), passwd(4), prof_attr(4), user_attr(4), attributes(5)

The output from the -g option to nscd is subject to change. Do not rely upon it as a programming interface.