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.. 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
.. _man_named:
named - Internet domain name server
-----------------------------------
Synopsis
~~~~~~~~
:program:`named` [ [**-4**] | [**-6**] ] [**-c** config-file] [**-C**] [**-d** debug-level] [**-D** string] [**-E** engine-name] [**-f**] [**-g**] [**-L** logfile] [**-M** option] [**-m** flag] [**-n** #cpus] [**-p** port] [**-s**] [**-S** #max-socks] [**-t** directory] [**-U** #listeners] [**-u** user] [**-v**] [**-V**] [**-X** lock-file] [**-x** cache-file]
Description
~~~~~~~~~~~
``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, ``named`` reads the default
configuration file ``/etc/named.conf``, reads any initial data, and
listens for queries.
Options
~~~~~~~
``-4``
This option tells ``named`` to use only IPv4, even if the host machine is capable of IPv6. ``-4`` and
``-6`` are mutually exclusive.
``-6``
This option tells ``named`` to use only IPv6, even if the host machine is capable of IPv4. ``-4`` and
``-6`` are mutually exclusive.
``-c config-file``
This option tells ``named`` to use ``config-file`` as its configuration file instead of the default,
``/etc/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.
``-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.
``-d debug-level``
This option sets the daemon's debug level to ``debug-level``. Debugging traces from
``named`` become more verbose as the debug level increases.
``-D string``
This option specifies a string that is used to identify a instance of ``named``
in a process listing. The contents of ``string`` are not examined.
``-E engine-name``
When applicable, this option specifies the hardware to use for cryptographic
operations, such as a secure key store used for signing.
When BIND 9 is built with OpenSSL, this needs to be set to the OpenSSL
engine identifier that drives the cryptographic accelerator or
hardware service module (usually ``pkcs11``). When BIND is
built with native PKCS#11 cryptography (``--enable-native-pkcs11``), it
defaults to the path of the PKCS#11 provider library specified via
``--with-pkcs11``.
``-f``
This option runs the server in the foreground (i.e., do not daemonize).
``-g``
This option runs the server in the foreground and forces all logging to ``stderr``.
``-L logfile``
This option sets the log to the file ``logfile`` by default, instead of the system log.
``-M option``
This option sets the default (comma-separated) memory context
options. The possible flags are:
- ``external``: use system-provided memory allocation functions; this
is the implicit default.
- ``internal``: use the internal memory manager.
- ``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 ``named`` has been compiled with
``--enable-developer``.
- ``nofill``: disable the behavior enabled by ``fill``; this is the
implicit default unless ``named`` has been compiled with
``--enable-developer``.
``-m flag``
This option turns on memory usage debugging flags. Possible flags are ``usage``,
``trace``, ``record``, ``size``, and ``mctx``. These correspond to the
``ISC_MEM_DEBUGXXXX`` flags described in ``<isc/mem.h>``.
``-n #cpus``
This option controls the number of CPUs that ``named`` assumes the
presence of. If not specified, ``named`` tries to determine the
number of CPUs present automatically; if it fails, a single CPU is
assumed to be present.
``named`` creates two threads per each CPU present (one thread for
receiving and sending client traffic and another thread for sending
and receiving resolver traffic) and then on top of that a single
thread for handling time-based events.
``-p port``
This option listens for queries on ``port``. If not specified, the default is
port 53.
``-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.
``-S #max-socks``
This option allows ``named`` to use up to ``#max-socks`` sockets. The default value is
21000 on systems built with default configuration options, and 4096
on systems built with ``configure --with-tuning=small``.
.. warning::
This option should be unnecessary for the vast majority of users.
The use of this option could even be harmful, because the specified
value may exceed the limitation of the underlying system API. It
is therefore set only when the default configuration causes
exhaustion of file descriptors and the operational environment is
known to support the specified number of sockets. Note also that
the actual maximum number is normally slightly fewer than the
specified value, because ``named`` reserves some file descriptors
for its internal use.
``-t directory``
This option tells ``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 ``-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.
``-U #listeners``
This option tells ``named`` the number of ``#listeners`` worker threads to listen on, for incoming UDP packets on
each address. If not specified, ``named`` calculates a default
value based on the number of detected CPUs: 1 for 1 CPU, and the
number of detected CPUs minus one for machines with more than 1 CPU.
This cannot be increased to a value higher than the number of CPUs.
If ``-n`` has been set to a higher value than the number of detected
CPUs, then ``-U`` may be increased as high as that value, but no
higher. On Windows, the number of UDP listeners is hardwired to 1 and
this option has no effect.
``-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, ``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 ``-u`` option only works when ``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``.
``-v``
This option reports the version number and exits.
``-V``
This option reports the version number, build options, supported
cryptographics algorithms, and exits.
``-X lock-file``
This option acquires a lock on the specified file at runtime; this helps to
prevent duplicate ``named`` instances from running simultaneously.
Use of this option overrides the ``lock-file`` option in
``named.conf``. If set to ``none``, the lock file check is disabled.
``-x cache-file``
This option loads data from ``cache-file`` into the cache of the default view.
.. warning::
This option must not be used in normal operations. It is only of interest to BIND 9
developers and may be removed or changed in a future release.
Signals
~~~~~~~
In routine operation, signals should not be used to control the
nameserver; ``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 ``named`` configuration file is too complex to describe in detail
here. A complete description is provided in the BIND 9 Administrator
Reference Manual.
``named`` inherits the ``umask`` (file creation mode mask) from the
parent process. If files created by ``named``, such as journal files,
need to have custom permissions, the ``umask`` should be set explicitly
in the script used to start the ``named`` process.
Files
~~~~~
``/etc/named.conf``
The default configuration file.
``/var/run/named/named.pid``
The default process-id file.
See Also
~~~~~~~~
:rfc:`1033`, :rfc:`1034`, :rfc:`1035`, :manpage:`named-checkconf(8)`, :manpage:`named-checkzone(8)`, :manpage:`rndc(8)`, :manpage:`named.conf(5)`, BIND 9 Administrator Reference Manual.
|
