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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
     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:
            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.
            If set to TRUE, the NIS backend  for  the  getservbyname(3)  and
            getservbyname_r(3)   functions   will   assume   that  the  ser-
            vices.byservicename NIS map exists and is authoritative, partic-
            ularly 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.
            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




     This page is part of release 4.16 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

Linux 2013-02-13 NSS(5)

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