nscd
—
name service caching daemon
nscd |
[-dnst ] [-i
cachename] [-I
cachename] |
The nscd
utility is the system caching daemon. It can
cache almost all types of data and is basically intended to be used with the
nsswitch
subsystem. The cache is actually per-user.
This means that each user can work only with the cached data that were cached
by themselves, and cannot poison the cache of other users. The
nscd
utility supports two types of caching:
- Type
- Description
- Common caching
- Each cached element is the key+value pair. This type of caching supports
policies which are applied when maximum number of cached elements is
exceeded. Three policies are available:
FIFO
(first in - first out), LRU
(least recently used)
and LFU
(least frequently used). This type of
caching is used with the getXXXbyname
() family of
functions.
- Multipart caching
- Each cached element is the part of the elements sequence. This type of
caching is intended to be used with the
getXXXent
() family of functions.
The nscd
utility is able not only to cache
elements, but to perform the actual nsswitch lookups by itself. To enable
this feature, use the perform-actual-lookups parameter
in
nscd.conf(5).
The nscd
utility recognizes the following
runtime options:
-n
- Do not daemonize;
nscd
will not fork or disconnect
itself from the terminal.
-s
- Single-threaded mode. Forces using only one thread for all processing
purposes (it overrides the threads parameter in the
nscd.conf(5)
file).
-t
- Trace mode. All trace messages will be written to stdout. This mode is
usually used with
-n
and
-s
flags are used for debugging purposes.
-i
cachename
- Invalidates personal cache. When specified,
nscd
acts as the administration tool. It asks the already running
nscd
to invalidate the specified part of the cache
of the calling user. For example, sometimes you may want to invalidate
your “hosts
” cache. You can specify
“all
” as the
cachename to invalidate your personal cache as a
whole. You cannot use this option for the cachename
for which the perform-actual-lookups option is
enabled.
-I
cachename
- Invalidates the cache for every user. When specified,
nscd
acts as the administration tool. It asks the
already running nscd
to invalidate the specified
part of the cache for every user. You can specify
“all
” as the
cachename to invalidate the whole cache. Only the
root can use this option.
- /etc/nscd.conf
- The default configuration file.