.\" $NetBSD: nsswitch.conf.5,v 1.28.38.1 2019/09/02 16:39:20 martin Exp $ .\" .\" Copyright (c) 1997, 1998, 1999 The NetBSD Foundation, Inc. .\" All rights reserved. .\" .\" This code is derived from software contributed to The NetBSD Foundation .\" by Luke Mewburn. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" .\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS .\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED .\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR .\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS .\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR .\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF .\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS .\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN .\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE .\" POSSIBILITY OF SUCH DAMAGE. .\" .Dd October 25, 2009 .Dt NSSWITCH.CONF 5 .Os .Sh NAME .Nm nsswitch.conf .Nd name-service switch configuration file .Sh DESCRIPTION The .Nm file specifies how the .Xr nsdispatch 3 (name-service switch dispatcher) routines in the C library should operate. .Pp The configuration file controls how a process looks up various databases containing information regarding hosts, users (passwords), groups, netgroups, etc. Each database comes from a source (such as local files, DNS, and .Tn NIS ) , and the order to look up the sources is specified in .Nm nsswitch.conf . .Pp Each entry in .Nm consists of a database name, and a space separated list of sources. Each source can have an optional trailing criterion that determines whether the next listed source is used, or the search terminates at the current source. Each criterion consists of one or more status codes, and actions to take if that status code occurs. .Ss Sources The following sources are implemented: .Bl -column "multicast_dns" -offset indent -compact .It Sy Source Description .It files Local files, such as .Pa /etc/hosts , and .Pa /etc/passwd . .It dns Internet Domain Name System. .Dq hosts and .Dq networks use .Sy IN class entries, all other databases use .Sy HS class (Hesiod) entries. .It mdnsd Use .Xr mdnsd 8 for .Dq hosts lookups, acting as both a system-wide cache for normal unicast DNS as well as providing multicast DNS .Dq ( zeroconf ) lookups. .It multicast_dns Use .Xr mdnsd 8 only for multicast DNS .Dq hosts lookups. This would normally be used in conjunction with .Dq dns , which would then provide unicast DNS resolver functions. .It nis NIS (formerly YP) .It compat support .Sq +/- in the .Dq passwd and .Dq group databases. If this is present, it must be the only source for that entry. .El .Ss Databases The following databases are used by the following C library functions: .Bl -column "netgroup" -offset indent -compact .It Sy Database Used by .It group Ta Xr getgrent 3 .It hosts Ta Xr gethostbyname 3 .It netgroup Ta Xr getnetgrent 3 .It networks Ta Xr getnetbyname 3 .It passwd Ta Xr getpwent 3 .It shells Ta Xr getusershell 3 .El .Ss Status codes The following status codes are available: .Bl -column "tryagain" -offset indent -compact .It Sy Status Description .It success The requested entry was found. .It notfound The entry is not present at this source. .It tryagain The source is busy, and may respond to retries. .It unavail The source is not responding, or entry is corrupt. .El .Ss Actions For each of the status codes, one of two actions is possible: .Bl -column "continue" -offset indent -compact .It Sy Action Description .It continue Try the next source .It return Return with the current result .El .Ss Format of file A .Tn BNF description of the syntax of .Nm is: .Bl -column "" -offset indent .It ::= ":" [ []]* .It ::= "[" + "]" .It ::= "=" .It ::= "success" | "notfound" | "unavail" | "tryagain" .It ::= "return" | "continue" .El .Pp Each entry starts on a new line in the file. A .Sq # delimits a comment to end of line. Blank lines are ignored. A .Sq \e at the end of a line escapes the newline, and causes the next line to be a continuation of the current line. All entries are case-insensitive. .Pp The default criteria is to return on .Dq success , and continue on anything else (i.e, .Li [success=return notfound=continue unavail=continue tryagain=continue] ). .Ss Compat mode: +/- syntax In historical multi-source implementations, the .Sq + and .Sq - characters are used to specify the importing of user password and group information from .Tn NIS . Although .Nm provides alternative methods of accessing distributed sources such as .Tn NIS , specifying a sole source of .Dq compat will provide the historical behaviour. .Pp An alternative source for the information accessed via .Sq +/- can be used by specifying .Dq passwd_compat: source . .Dq source in this case can be .Sq dns , .Sq nis , or any other source except for .Sq files and .Sq compat . .Ss Notes Historically, many of the databases had enumeration functions, often of the form .Fn getXXXent . These made sense when the databases were in local files, but don't make sense or have lesser relevance when there are possibly multiple sources, each of an unknown size. The interfaces are still provided for compatibility, but the source may not be able to provide complete entries, or duplicate entries may be retrieved if multiple sources that contain similar information are specified. .Pp To ensure compatibility with previous and current implementations, the .Dq compat source must appear alone for a given database. .Ss Default source lists If, for any reason, .Nm nsswitch.conf doesn't exist, or it has missing or corrupt entries, .Xr nsdispatch 3 will default to an entry of .Dq files for the requested database. Exceptions are: .Bl -column passwd_compat "files dns" -offset indent .It Sy Database Default source list .It group compat .It group_compat nis .It hosts files dns .It netgroup files [notfound=return] nis .It passwd compat .It passwd_compat nis .El .Sh FILES .Bl -tag -width /etc/nsswitch.conf -compact .It Pa /etc/nsswitch.conf The file .Nm resides in .Pa /etc . .El .Sh EXAMPLES To lookup hosts in .Pa /etc/hosts and then from the DNS, and lookup user information from .Tn NIS then files, use: .Bl -column "passwd:" -offset indent .It hosts: files dns .It passwd: nis [notfound=return] files .It group: nis [notfound=return] files .El .Pp The criteria .Dq [notfound=return] sets a policy of "if the user is notfound in nis, don't try files." This treats nis as the authoritative source of information, except when the server is down. .Sh SEE ALSO .Xr getent 1 , .Xr nsdispatch 3 , .Xr resolv.conf 5 , .Xr named 8 , .Xr ypbind 8 .Sh HISTORY The .Nm file format first appeared in .Nx 1.4 . .Sh AUTHORS .An Luke Mewburn .Aq lukem@NetBSD.org wrote this freely distributable name-service switch implementation, using ideas from the .Tn ULTRIX .Xr svc.conf 5 and .Tn Solaris .Xr nsswitch.conf 4 manual pages.