NAME    [Toc]    [Back]

       nsswitch.conf - name-service switch configuration file

DESCRIPTION    [Toc]    [Back]

       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  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.

   Sources    [Toc]    [Back]
       The following  sources  may  be  used:  Description  Local
       files,  such  as  /etc/hosts  and  /etc/passwd.   Internet
       Domain Name System.  ``hosts'' and `networks' use IN class
       entries,   all  other  databases  use  HS  class  (Hesiod)
       entries.   NIS  (formerly  YP)  support   `+/-'   in   the
       ``passwd'' and ``group'' databases. If this is present, it
       must be the only source for that entry.

   Databases    [Toc]    [Back]
       The following databases use the switch:  Used  by  getesdfent()
 getesdvent() getesfient() getespwent() getestcent()
       getgrent()  gethostbyname()  getnetgrent()  getnetbyname()
       getpwent() getprotobyname() getrpcent() getnameinfo()

   Status Codes    [Toc]    [Back]
       The  following  status  codes  are  available:  Codes  The
       requested entry was found.  The entry was not  present  at
       this  source.   The  source  is  busy  and  may respond to
       retires.  The source is not responding, or entry  is  corrupt.


   Actions    [Toc]    [Back]
       For each of the status codes, one if two actions is possible:
 Description Try the next  source.   Return  with  the
       current result.

   Format of the File    [Toc]    [Back]
       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=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 accessing  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    [Toc]    [Back]
       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
       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.

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

   Default Source Lists    [Toc]    [Back]
       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: Default Source List compat nis files dns  files
       [notfound=return] nis compat nis

FILES    [Toc]    [Back]

       /etc/nsswitch.conf

EXAMPLES    [Toc]    [Back]

       To  look up 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    [Toc]    [Back]

       getesdfent(3),   getesdvent(3),   getesfient(3),   getespwent(3), getestcent(3), getgrent()getprent(3),  gethostbyname(3),   getnetgrent(3),  getnetbyname(3),  getpwent(3),
       getprotobyname(3), getnameinfo(3), nsdispatch(3)



                                                 nsswitch.conf(5)