nss(5) - man - phpMan

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 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 data‐
       bases 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  infor‐
              mation 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) func‐
              tions 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 pri‐
              mary 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

EXAMPLES
       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  5.10 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/.



Linux                                        2020-06-09                                       NSS(5)