nss(5)                                                                                                                    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 adminis-
       trator  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  sacrifize  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  gener-
              ated.


       SERVICES_AUTHORITATIVE = TRUE|FALSE
              If  set  to  TRUE,  the  NIS  backend  for  the  getservbyname(3) and getservbyname_r(3) function will assume ser-
              vices.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 into a network communication  with
              the server to get the next entry.



EXAMPLE
       The default configuration corresponds to the following configuration file:

       NETID_AUTHORITATIVE=FALSE
       SERVICES_AUTHORITATIVE=FALSE
       SETENT_BATCH_READ=FALSE



FILES
       /etc/default/nss


AUTHOR
       Ulrich Drepper <drepperATredhat.com>


SEE ALSO
       nsswitch.conf



nss                                                         May 2006                                                      nss(5)