Open Source Software

nss(5)



NAME

   nss - Name Service Switch configuration file

DESCRIPTION

   Each  call  to  a  function which retrieves data from a system database
   like the password or group database is  handled  by  the  Name  Service
   Switch  implementation  in  the  GNU  C  library.  The various services
   provided  are  implemented  by  independent  modules,  each  of   which
   naturally varies widely from the other.

   The  default  implementations  coming  with  the  GNU  C library are by
   default conservative and do not use unsafe data.  This  might  be  very
   costly  in  some  situations,  especially when the databases are large.
   Some modules allow the system administrator to request taking shortcuts
   if  these  are known to be safe.  It is then the system administrator's
   responsibility to ensure the assumption is correct.

   There are other modules where the implementation changed over time.  If
   an  implementation  used  to sacrifice speed for memory consumption, it
   might create problems if the preference is switched.

   The /etc/default/nss file contains a number  of  variable  assignments.
   Each  variable controls the behavior of one or more NSS modules.  White
   spaces are ignored.  Lines beginning with '#' are treated as comments.

   The variables currently recognized are:

   NETID_AUTHORITATIVE = TRUE|FALSE
          If set to TRUE, the NIS backend for the  initgroups(3)  function
          will  accept  the  information  from the netid.byname NIS map as
          authoritative.  This can speed up the function significantly  if
          the  group.byname map is large.  The content of the netid.byname
          map is used as is.  The system administrator has to make sure it
          is correctly generated.

   SERVICES_AUTHORITATIVE = TRUE|FALSE
          If  set  to  TRUE,  the NIS backend for the getservbyname(3) and
          getservbyname_r(3)    functions    will    assume    that    the
          services.byservicename  NIS  map  exists  and  is authoritative,
          particularly that it contains both keys with /proto and  without
          /proto  for both primary service names and service aliases.  The
          system administrator has to make sure it is correctly generated.

   SETENT_BATCH_READ = TRUE|FALSE
          If set  to  TRUE,  the  NIS  backend  for  the  setpwent(3)  and
          setgrent(3)  functions will read the entire database at once and
          then hand out the requests one by one  from  memory  with  every
          corresponding  getpwent(3)  or  getgrent(3)  call  respectively.
          Otherwise, each getpwent(3) or getgrent(3) call might result  in
          a network communication with the server to get the next entry.

FILES

   /etc/default/nss

EXAMPLE

   The  default  configuration  corresponds to the following configuration
   file:

   NETID_AUTHORITATIVE=FALSE
   SERVICES_AUTHORITATIVE=FALSE
   SETENT_BATCH_READ=FALSE

SEE ALSO

   nsswitch.conf

COLOPHON

   This page is part of release 4.09 of the Linux  man-pages  project.   A
   description  of  the project, information about reporting bugs, and the
   latest    version    of    this    page,    can     be     found     at
   https://www.kernel.org/doc/man-pages/.



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