NSS(5)                              Linux Programmer's Manual                              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 natu‐
       rally 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 short‐
       cuts  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  con‐
       trols 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 author‐
              itative, 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.  Oth‐
              erwise,  each  getpwent(3) or getgrent(3) call might result in a network communica‐
              tion 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 3.74 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 http://www.kernel.org/doc/man-pages/.



Linux                                       2013-02-13                                     NSS(5)