NSS(5)                     Linux Programmer's Manual                    NSS(5)

       nss - Name Service Switch configuration file

       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 pro-
       vided 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 de-
       fault 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:

              If set to TRUE, the NIS backend for the  initgroups(3)  function
              will accept the information from the netid.byname NIS map as au-
              thoritative.  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.

              If  set  to  TRUE,  the NIS backend for the getservbyname(3) and
              getservbyname_r(3) functions will assume that  the  services.by-
              servicename  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 ad-
              ministrator has to make sure it is correctly generated.

              If set to TRUE, the NIS backend for  the  setpwent(3)  and  set-
              grent(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.


       The  default  configuration  corresponds to the following configuration



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Linux                             2013-02-13                            NSS(5)
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