NSSWITCH.CONF(5)          NetBSD 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, net-
     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 data-
                            bases use HS class (Hesiod) entries.
           mdnsd            Use mdnsd(8) for ``hosts'' lookups, acting as both
                            a system-wide cache for normal unicast DNS as well
                            as providing multicast DNS (``zeroconf'') lookups.
           multicast_dns    Use mdnsd(8) only for multicast DNS ``hosts''
                            lookups.  This would normally be used in conjunc-
                            tion with ``dns'', which would then provide uni-
                            cast DNS resolver functions.
           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)
           netgroup    getnetgrent(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 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
           netgroup         files [notfound=return] nis
           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.

SEE ALSO
     getent(1), nsdispatch(3), resolv.conf(5), named(8), ypbind(8)

HISTORY
     The nsswitch.conf file format first appeared 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.

NetBSD 6.0                     October 25, 2009                     NetBSD 6.0

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