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34 .\" $FreeBSD: src/share/man/man5/nsswitch.conf.5,v 1.18 2007/10/19 00:16:29 bushman Exp $
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42 .Nd name-service switch configuration file
46 file specifies how the
48 (name-service switch dispatcher) routines in the C library should operate.
50 The configuration file controls how a process looks up various databases
51 containing information regarding hosts, users (passwords), groups, etc.
52 Each database comes from a source (such as local files, DNS,
54 and cache), and the order to look up the sources is specified in
59 consists of a database name, and a space separated list of sources.
60 Each source can have an optional trailing criterion that determines
61 whether the next listed source is used, or the search terminates at
63 Each criterion consists of one or more status codes, and actions to
64 take if that status code occurs.
66 The following sources are implemented:
68 .Bl -tag -width Source -compact
77 Internet Domain Name System.
83 class entries, all other databases use
85 class (Hesiod) entries.
96 If this is present, it must be the only source for that entry.
103 The following databases are used by the following C library functions:
105 .Bl -tag -width networks -compact
117 .Xr gethostbyaddr 3 ,
118 .Xr gethostbyaddr_r 3 ,
119 .Xr gethostbyname 3 ,
120 .Xr gethostbyname2 3 ,
121 .Xr gethostbyname_r 3 ,
122 .Xr getipnodebyaddr 3 ,
123 .Xr getipnodebyname 3
126 .Xr getnetbyaddr_r 3 ,
142 .Xr getrpcbynumber 3 ,
146 .Xr getprotobynumber 3 ,
150 The following status codes are available:
152 .Bl -tag -width tryagain -compact
156 The requested entry was found.
158 The entry is not present at this source.
160 The source is busy, and may respond to retries.
162 The source is not responding, or entry is corrupt.
165 For each of the status codes, one of two actions is possible:
167 .Bl -tag -width continue -compact
173 Return with the current result
178 description of the syntax of
182 .Bl -tag -width <criterion> -compact
185 <database> ":" [<source> [<criteria>]]*
191 <status> "=" <action>
194 "success" | "notfound" | "unavail" | "tryagain"
197 "return" | "continue"
200 Each entry starts on a new line in the file.
203 delimits a comment to end of line.
204 Blank lines are ignored.
207 at the end of a line escapes the newline, and causes the next line to
208 be a continuation of the current line.
209 All entries are case-insensitive.
211 The default criteria is to return on
213 and continue on anything else (i.e,
214 .Li "[success=return notfound=continue unavail=continue tryagain=continue]" ) .
216 You can enable caching for the particular database by specifying
218 as the first source in the
221 You should also enable caching for this database in
223 If for the particular query
225 source returns success, no further sources are queried.
226 On the other hand, if there are no previously cached data, the
227 query result will be placed into the cache right after
228 all other sources are processed.
233 daemon to be running.
234 .Ss Compat mode: +/- syntax
235 In historical multi-source implementations, the
239 characters are used to specify the importing of user password and
240 group information from
244 provides alternative methods of accessing distributed sources such as
246 specifying a sole source of
248 will provide the historical behaviour.
250 An alternative source for the information accessed via
252 can be used by specifying
253 .Dq passwd_compat: source .
259 any other source except for
264 Historically, many of the databases had enumeration functions, often of
267 These made sense when the databases were in local files, but do not make
268 sense or have lesser relevance when there are possibly multiple sources,
269 each of an unknown size.
270 The interfaces are still provided for compatibility, but the source
271 may not be able to provide complete entries, or duplicate entries may
272 be retrieved if multiple sources that contain similar information are
275 To ensure compatibility with previous and current implementations, the
277 source must appear alone for a given database.
278 .Ss Default source lists
281 does not exist, or it has missing or corrupt entries,
283 will default to an entry of
285 for the requested database.
288 .Bl -tag -width services_compat -compact
290 .Sy "Default source list"
307 .Bl -tag -width /etc/nsswitch.conf -compact
308 .It Pa /etc/nsswitch.conf
315 To lookup hosts in cache, then in
317 and then from the DNS, and lookup user information from
321 .Bl -tag -width passwd: -compact
325 nis [notfound=return] files
327 nis [notfound=return] files
331 .Dq [notfound=return]
332 sets a policy of "if the user is notfound in nis, do not try files."
333 This treats nis as the authoritative source of information, except
334 when the server is down.
336 If system got compiled with
344 provides stubs for compatibility with NSS modules
350 However, these stubs only support the use of the
365 file format first appeared in
367 It was imported from the
369 Project, where it appeared first in
374 wrote this freely distributable name-service switch implementation,