.. Copyright (C) Internet Systems Consortium, Inc. ("ISC")
..
.. SPDX-License-Identifier: MPL-2.0
..
.. This Source Code Form is subject to the terms of the Mozilla Public
.. License, v. 2.0.  If a copy of the MPL was not distributed with this
.. file, you can obtain one at https://mozilla.org/MPL/2.0/.
..
.. See the COPYRIGHT file distributed with this work for additional
.. information regarding copyright ownership.

.. highlight: console

.. iscman:: named
.. program:: named
.. _man_named:

named - Internet domain name server
-----------------------------------

Synopsis
~~~~~~~~

:program:`named` [ [**-4**] | [**-6**] ] [**-c** config-file] [**-C**] [**-d** debug-level] [**-D** string] [**-f**] [**-g**] [**-L** logfile] [**-M** option] [**-m** flag] [**-n** #cpus] [**-p** port] [**-s**] [**-t** directory] [**-u** user] [**-v**] [**-V**] ]

Description
~~~~~~~~~~~

:program:`named` is a Domain Name System (DNS) server, part of the BIND 9
distribution from ISC. For more information on the DNS, see :rfc:`1033`,
:rfc:`1034`, and :rfc:`1035`.

When invoked without arguments, :program:`named` reads the default
configuration file |named_conf|, reads any initial data, and
listens for queries.

Options
~~~~~~~

.. option:: -4

   This option tells :program:`named` to use only IPv4, even if the host machine is capable of IPv6. :option:`-4` and
   :option:`-6` are mutually exclusive.

.. option:: -6

   This option tells :program:`named` to use only IPv6, even if the host machine is capable of IPv4. :option:`-4` and
   :option:`-6` are mutually exclusive.

.. option:: -c config-file

   This option tells :program:`named` to use ``config-file`` as its configuration file instead of the default,
   |named_conf|. To ensure that the configuration file
   can be reloaded after the server has changed its working directory
   due to to a possible ``directory`` option in the configuration file,
   ``config-file`` should be an absolute pathname.

.. option:: -C

   This option prints out the default built-in configuration and exits.

   NOTE: This is for debugging purposes only and is not an
   accurate representation of the actual configuration used by :iscman:`named`
   at runtime.

.. option:: -d debug-level

   This option sets the daemon's debug level to ``debug-level``. Debugging traces from
   :program:`named` become more verbose as the debug level increases.

.. option:: -D string

   This option specifies a string that is used to identify a instance of :program:`named`
   in a process listing. The contents of ``string`` are not examined.

.. option:: -f

   This option runs the server in the foreground (i.e., do not daemonize).

.. option:: -F

   This options turns on FIPS (US Federal Information Processing Standards)
   mode if the underlying crytographic library supports running in FIPS
   mode.

.. option:: -g

   This option runs the server in the foreground and forces all logging to ``stderr``.

.. option:: -L logfile

   This option sets the log to the file ``logfile`` by default, instead of the system log.

.. option:: -M option

   This option sets the default (comma-separated) memory context
   options. The possible flags are:

   - ``fill``: fill blocks of memory with tag values when they are
     allocated or freed, to assist debugging of memory problems; this is
     the implicit default if :program:`named` has been compiled with
     ``--enable-developer``.

   - ``nofill``: disable the behavior enabled by ``fill``; this is the
     implicit default unless :program:`named` has been compiled with
     ``--enable-developer``.

.. option:: -m flag

   This option turns on memory usage debugging flags. Possible flags are ``usage``,
   ``trace`` and ``record``. These correspond to the
   ``ISC_MEM_DEBUGXXXX`` flags described in ``<isc/mem.h>``.

.. option:: -n #cpus

   This option creates ``#cpus`` worker threads to take advantage of multiple CPUs. If
   not specified, :program:`named` tries to determine the number of CPUs
   present and creates one thread per CPU. If it is unable to determine
   the number of CPUs, a single worker thread is created.

.. option:: -p value

   This option specifies the port(s) on which the server will listen
   for queries. If ``value`` is of the form ``<portnum>`` or
   ``dns=<portnum>``, the server will listen for DNS queries on
   ``portnum``; if not not specified, the default is port 53. If
   ``value`` is of the form ``tls=<portnum>``, the server will
   listen for TLS queries on ``portnum``; the default is 853.
   If ``value`` is of the form ``https=<portnum>``, the server will
   listen for HTTPS queries on ``portnum``; the default is 443.
   If ``value`` is of the form ``http=<portnum>``, the server will
   listen for HTTP queries on ``portnum``; the default is 80.

.. option:: -s

   This option writes memory usage statistics to ``stdout`` on exit.

.. note::

      This option is mainly of interest to BIND 9 developers and may be
      removed or changed in a future release.

.. option:: -t directory

   This option tells :program:`named` to chroot to ``directory`` after processing the command-line arguments, but
   before reading the configuration file.

.. warning::

      This option should be used in conjunction with the :option:`-u` option,
      as chrooting a process running as root doesn't enhance security on
      most systems; the way ``chroot`` is defined allows a process
      with root privileges to escape a chroot jail.

.. option:: -U #listeners

   This option has been removed. Attempts to use it now result in a warning.

.. option:: -u user

   This option sets the setuid to ``user`` after completing privileged operations, such as
   creating sockets that listen on privileged ports.

.. note::

      On Linux, :program:`named` uses the kernel's capability mechanism to drop
      all root privileges except the ability to ``bind`` to a
      privileged port and set process resource limits. Unfortunately,
      this means that the :option:`-u` option only works when :program:`named` is run
      on kernel 2.2.18 or later, or kernel 2.3.99-pre3 or later, since
      previous kernels did not allow privileges to be retained after
      ``setuid``.

.. option:: -v

   This option reports the version number and exits.

.. option:: -V

   This option reports the version number, build options, supported
   cryptographics algorithms, and exits.

.. option:: -X lock-file

   This option has been removed and using it will cause a fatal error.

Signals
~~~~~~~

In routine operation, signals should not be used to control the
nameserver; :iscman:`rndc` should be used instead.

SIGHUP
   This signal forces a reload of the server.

SIGINT, SIGTERM
   These signals shut down the server.

The result of sending any other signals to the server is undefined.

Configuration
~~~~~~~~~~~~~

The :program:`named` configuration file is too complex to describe in detail
here. A complete description is provided in the BIND 9 Administrator
Reference Manual.

:program:`named` inherits the ``umask`` (file creation mode mask) from the
parent process. If files created by :program:`named`, such as journal files,
need to have custom permissions, the ``umask`` should be set explicitly
in the script used to start the :program:`named` process.

Files
~~~~~

|named_conf|
   The default configuration file.

|named_pid|
   The default process-id file.

See Also
~~~~~~~~

:rfc:`1033`, :rfc:`1034`, :rfc:`1035`, :iscman:`named-checkconf(8) <named-checkconf>`, :iscman:`named-checkzone(8) <named-checkzone>`, :iscman:`rndc(8) <rndc>`, :iscman:`named.conf(5) <named.conf>`, BIND 9 Administrator Reference Manual.
