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nsswitch.conf(5)

NAME

     nsswitch.conf -- name-service switch configuration file

DESCRIPTION

     The nsswitch.conf file specifies how the nsdispatch(3) (name-service
     switch dispatcher) routines in the C library should operate.

     The configuration file controls how a process looks up various databases
     containing information regarding hosts, users (passwords), groups, etc.
     Each database comes from a source (such as local files, DNS, and NIS),
     and the order to look up the sources is specified in nsswitch.conf.

     Each entry in nsswitch.conf consists of a database name, and a space sep-
     arated list of sources.  Each source can have an optional trailing crite-
     rion 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.

   Sources
     The following sources are implemented:

     Source  Description
     files   Local files, such as /etc/hosts, and /etc/passwd.
     dns     Internet Domain Name System.  ``hosts'' and `networks' use IN
	     class entries, all other databases use HS class (Hesiod) entries.
     nis     NIS (formerly YP)
     compat  support `+/-' in the ``passwd'' and ``group'' databases.  If this
	     is present, it must be the only source for that entry.

   Databases
     The following databases are used by the following C library functions:

     Database  Used by
     group     getgrent(3)
     hosts     gethostbyname(3)
     networks  getnetbyname(3)
     passwd    getpwent(3)
     shells    getusershell(3)

   Status codes
     The following status codes are available:

     Status    Description
     success   The requested entry was found.
     notfound  The entry is not present at this source.
     tryagain  The source is busy, and may respond to retries.
     unavail   The source is not responding, or entry is corrupt.

   Actions
     For each of the status codes, one of two actions is possible:

     Action    Description
     continue  Try the next source
     return    Return with the current result

   Format of file
     A BNF description of the syntax of nsswitch.conf is:
     end of line.  Blank lines are ignored.  A `\' 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.

     The default criteria is to return on ``success'', and continue on any-
     thing else (i.e, [success=return notfound=continue unavail=continue
     tryagain=continue]).

   Compat mode: +/- syntax
     In historical multi-source implementations, the `+' and `-' characters
     are used to specify the importing of user password and group information
     from NIS.	Although nsswitch.conf provides alternative methods of access-
     ing distributed sources such as NIS, specifying a sole source of
     ``compat'' will provide the historical behaviour.

     An alternative source for the information accessed via `+/-' can be used
     by specifying ``passwd_compat: source''.  ``source'' in this case can be
     `dns', `nis', or any other source except for `files' and `compat'.

   Notes
     Historically, many of the databases had enumeration functions, often of
     the form getXXXent().  These made sense when the databases were in local
     files, but don't make sense or have lesser relevance when there are pos-
     sibly multiple sources, each of an unknown size.  The interfaces are
     still provided for compatibility, but the source may not be able to pro-
     vide complete entries, or duplicate entries may be retrieved if multiple
     sources that contain similar information are specified.

     To ensure compatibility with previous and current implementations, the
     ``compat'' source must appear alone for a given database.

   Default source lists
     If, for any reason, nsswitch.conf doesn't exist, or it has missing or
     corrupt entries, nsdispatch(3) will default to an entry of ``files'' for
     the requested database.  Exceptions are:

     Database	    Default source list
     group	    compat
     group_compat   nis
     hosts	    files dns
     passwd	    compat
     passwd_compat  nis

FILES

     /etc/nsswitch.conf  The file nsswitch.conf resides in /etc.

EXAMPLES

     To lookup hosts in /etc/hosts and then from the DNS, and lookup user
     information from NIS then files, use:

     hosts:   files dns
     passwd:  nis [notfound=return] files
     group:   nis [notfound=return] files

     The criteria ``[notfound=return]'' sets a policy of "if the user is not-
     found in nis, don't try files."  This treats nis as the authoritative
     source of information, except when the server is down.

     Luke Mewburn <lukem@netbsd.org> wrote this freely distributable name-ser-
     vice switch implementation, using ideas from the ULTRIX svc.conf(5) and
     Solaris nsswitch.conf(4) manual pages.

FreeBSD 5.4			 June 21, 2004			   FreeBSD 5.4

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