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diff --git a/doc/arm/config-intro.inc.rst b/doc/arm/config-intro.inc.rst new file mode 100644 index 0000000..d041ecc --- /dev/null +++ b/doc/arm/config-intro.inc.rst @@ -0,0 +1,205 @@ +.. 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. + +.. _configuration: + +.. _sample_configuration: + +Configurations and Zone Files +============================= + +Introduction +------------ + +BIND 9 uses a single configuration file called :ref:`named.conf <named_conf>`. +which is typically located in either /etc/namedb or +/usr/local/etc/namedb. + + .. Note:: If :ref:`rndc<ops_rndc>` is being used locally (on the same host + as BIND 9) then an additional file :iscman:`rndc.conf` may be present, though + :iscman:`rndc` operates without this file. If :iscman:`rndc` is being run + from a remote host then an :iscman:`rndc.conf` file must be present as it + defines the link characteristics and properties. + +Depending on the functionality of the system, one or more zone files is +required. + +The samples given throughout this and subsequent chapters use a standard base +format for both the :iscman:`named.conf` and the zone files for **example.com**. The +intent is for the reader to see the evolution from a common base as features +are added or removed. + +.. _base_named_conf: + +``named.conf`` Base File +~~~~~~~~~~~~~~~~~~~~~~~~ + +This file illustrates the typical format and layout style used for +:iscman:`named.conf` and provides a basic logging service, which may be extended +as required by the user. + +.. code-block:: c + + // base named.conf file + // Recommended that you always maintain a change log in this file as shown here + // options clause defining the server-wide properties + options { + // all relative paths use this directory as a base + directory "/var"; + // version statement for security to avoid hacking known weaknesses + // if the real version number is revealed + version "not currently available"; + }; + + // logging clause + // log to /var/log/named/example.log all events from info UP in severity (no debug) + // uses 3 files in rotation swaps files when size reaches 250K + // failure messages that occur before logging is established are + // in syslog (/var/log/messages) + // + logging { + channel example_log { + // uses a relative path name and the directory statement to + // expand to /var/log/named/example.log + file "log/named/example.log" versions 3 size 250k; + // only log info and up messages - all others discarded + severity info; + }; + category default { + example_log; + }; + }; + +The :any:`logging` and :namedconf:ref:`options` blocks +and :any:`category`, :any:`channel`, +:any:`directory`, :any:`file`, and :any:`severity` +statements are all described further in the appropriate sections of this ARM. + +.. _base_zone_file: + +**example.com** base zone file +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The following is a complete zone file for the domain **example.com**, which +illustrates a number of common features. Comments in the file explain these +features where appropriate. Zone files consist of :ref:`Resource Records (RR) +<zone_file>`, which describe the zone's characteristics or properties. + +.. code-block:: + :linenos: + + ; base zone file for example.com + $TTL 2d ; default TTL for zone + $ORIGIN example.com. ; base domain-name + ; Start of Authority RR defining the key characteristics of the zone (domain) + @ IN SOA ns1.example.com. hostmaster.example.com. ( + 2003080800 ; serial number + 12h ; refresh + 15m ; update retry + 3w ; expiry + 2h ; minimum + ) + ; name server RR for the domain + IN NS ns1.example.com. + ; the second name server is external to this zone (domain) + IN NS ns2.example.net. + ; mail server RRs for the zone (domain) + 3w IN MX 10 mail.example.com. + ; the second mail servers is external to the zone (domain) + IN MX 20 mail.example.net. + ; domain hosts includes NS and MX records defined above + ; plus any others required + ; for instance a user query for the A RR of joe.example.com will + ; return the IPv4 address 192.168.254.6 from this zone file + ns1 IN A 192.168.254.2 + mail IN A 192.168.254.4 + joe IN A 192.168.254.6 + www IN A 192.168.254.7 + ; aliases ftp (ftp server) to an external domain + ftp IN CNAME ftp.example.net. + +This type of zone file is frequently referred to as a **forward-mapped zone +file**, since it maps domain names to some other value, while a +:ref:`reverse-mapped zone file<ipv4_reverse>` maps an IP address to a domain +name. The zone file is called **example.com** for no good reason except that +it is the domain name of the zone it describes; as always, users are free to +use whatever file-naming convention is appropriate to their needs. + +Other Zone Files +~~~~~~~~~~~~~~~~ + +Depending on the configuration additional zone files may or should be present. +Their format and functionality are briefly described here. + +localhost Zone File +~~~~~~~~~~~~~~~~~~~ + +All end-user systems are shipped with a ``hosts`` file (usually located in +/etc). This file is normally configured to map the name **localhost** (the name +used by applications when they run locally) to the loopback address. It is +argued, reasonably, that a forward-mapped zone file for **localhost** is +therefore not strictly required. This manual does use the BIND 9 distribution +file ``localhost-forward.db`` (normally in /etc/namedb/master or +/usr/local/etc/namedb/master) in all configuration samples for the following +reasons: + +1. Many users elect to delete the ``hosts`` file for security reasons (it is a + potential target of serious domain name redirection/poisoning attacks). + +2. Systems normally lookup any name (including domain names) using the + ``hosts`` file first (if present), followed by DNS. However, the + ``nsswitch.conf`` file (typically in /etc) controls this order (normally + **hosts: file dns**), allowing the order to be changed or the **file** value + to be deleted entirely depending on local needs. Unless the BIND + administrator controls this file and knows its values, it is unsafe to + assume that **localhost** is forward-mapped correctly. + +3. As a reminder to users that unnecessary queries for **localhost** form a + non-trivial volume of DNS queries on the public network, which affects DNS + performance for all users. + +Users may, however, elect at their discretion not to implement this file since, +depending on the operational environment, it may not be essential. + +The BIND 9 distribution file ``localhost-forward.db`` format is shown for +completeness and provides for both IPv4 and IPv6 localhost resolution. The zone +(domain) name is **localhost.** + +.. code-block:: + + $TTL 3h + localhost. SOA localhost. nobody.localhost. 42 1d 12h 1w 3h + NS localhost. + A 127.0.0.1 + AAAA ::1 + +.. NOTE:: Readers of a certain age or disposition may note the reference in this file to the late, + lamented Douglas Noel Adams. + +localhost Reverse-Mapped Zone File +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +This zone file allows any query requesting the name associated with the +loopback IP (127.0.0.1). This file is required to prevent unnecessary queries +from reaching the public DNS hierarchy. The BIND 9 distribution file +``localhost.rev`` is shown for completeness: + +.. code-block:: + + $TTL 1D + @ IN SOA localhost. root.localhost. ( + 2007091701 ; serial + 30800 ; refresh + 7200 ; retry + 604800 ; expire + 300 ) ; minimum + IN NS localhost. + 1 IN PTR localhost. |