nss(5) - Linux manual page (original) (raw)

nss(5) File Formats Manual nss(5)

NAME top

   nss - Name Service Switch configuration file

DESCRIPTION top

   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 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)](../man3/initgroups.3.html)
          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)](../man3/getservbyname.3.html)
          and [getservbyname_r(3)](../man3/getservbyname%5Fr.3.html) functions 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 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)](../man3/setpwent.3.html) and
          [setgrent(3)](../man3/setgrent.3.html) functions will read the entire database at once
          and then hand out the requests one by one from memory with
          every corresponding [getpwent(3)](../man3/getpwent.3.html) or [getgrent(3)](../man3/getgrent.3.html) call
          respectively.  Otherwise, each [getpwent(3)](../man3/getpwent.3.html) or [getgrent(3)](../man3/getgrent.3.html)
          call might result in a network communication with the
          server to get the next entry.

FILES top

   _/etc/default/nss_

EXAMPLES top

   The default configuration corresponds to the following
   configuration file:

       NETID_AUTHORITATIVE=FALSE
       SERVICES_AUTHORITATIVE=FALSE
       SETENT_BATCH_READ=FALSE

SEE ALSO top

   _nsswitch.conf_

COLOPHON top

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Linux man-pages 6.10 2024-05-02 nss(5)

Pages that refer to this page:nsswitch.conf(5), systemd-resolved.service(8)