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NSSWITCH.CONF(5)	       File Formats Manual		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  sepa-
     rated list of sources.  Each source can have an optional trailing criterion
     that  determines whether the next listed source is used, or the search ter-
     minates at the current source.  Each criterion consists of one or more sta-
     tus 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:

     <entry>	  ::= <database> ":" [<source> [<criteria>]]*
     <criteria>   ::= "[" <criterion>+ "]"
     <criterion>  ::= <status> "=" <action>
     <status>	  ::= "success" | "notfound" | "unavail" | "tryagain"
     <action>	  ::= "return" | "continue"

     Each entry starts on a new line in the file.  A `#' delimits a  comment  to
     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 anything
     else (i.e, [success=return notfound=continue unavail=continue tryagain=con-
     tinue]).

   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 accessing dis-
     tributed 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 possibly  mul-
     tiple  sources, each of an unknown size.  The interfaces are still provided
     for compatibility, but the source may not be able to provide  complete  en-
     tries,  or duplicate entries may be retrieved if multiple sources that con-
     tain 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 cor-
     rupt entries, nsdispatch(3) will default to an entry of "files" for the re-
     quested 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 infor-
     mation 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	notfound
     in  nis,  don't  try files." This treats nis as the authoritative source of
     information, except when the server is down.

SEE ALSO
     nsdispatch(3), resolv.conf(5), named(8), ypbind(8)

HISTORY
     The nsswitch.conf file format first appeared in FreeBSD 5.0.   It	was  im-
     ported from the NetBSD Project, where it appeared first in NetBSD 1.4.

AUTHORS
     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 		NSSWITCH.CONF(5)
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