bind  9.19.11
About: BIND 9.19 implements the Domain Name System (DNS) protocols for the Internet (see the Release Notes).
Source code distribution.
Unstable development release.
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  1. Introduction
  2. Reporting bugs and getting help
  3. Contributing to BIND
  4. Building BIND
  5. Automated testing
  6. Documentation
  7. Change log
  8. Acknowledgments


BIND (Berkeley Internet Name Domain) is a complete, highly portable implementation of the Domain Name System (DNS) protocol.

The BIND name server, named, can act as an authoritative name server, recursive resolver, DNS forwarder, or all three simultaneously. It implements views for split-horizon DNS, automatic DNSSEC zone signing and key management, catalog zones to facilitate provisioning of zone data throughout a name server constellation, response policy zones (RPZ) to protect clients from malicious data, response rate limiting (RRL) and recursive query limits to reduce distributed denial of service attacks, and many other advanced DNS features. BIND also includes a suite of administrative tools, including the dig and delv DNS lookup tools, nsupdate for dynamic DNS zone updates, rndc for remote name server administration, and more.

BIND 9 began as a complete rewrite of the BIND architecture that was used in versions 4 and 8. Internet Systems Consortium (, a 501(c)(3) US public benefit corporation dedicated to providing software and services in support of the Internet infrastructure, developed BIND 9 and is responsible for its ongoing maintenance and improvement. BIND is open source software licensed under the terms of the Mozilla Public License, version 2.0.

For a detailed list of changes made throughout the history of BIND 9, see the file CHANGES. See below for details on the CHANGES file format.

For up-to-date versions and release notes, see

For information about supported platforms, see the "Supported Platforms" section in the BIND 9 Administrator Reference Manual.

Reporting bugs and getting help

To report non-security-sensitive bugs or request new features, you may open an issue in the BIND 9 project on the ISC GitLab server at

Please note that, unless you explicitly mark the newly created issue as "confidential," it will be publicly readable. Please do not include any information in bug reports that you consider to be confidential unless the issue has been marked as such. In particular, if submitting the contents of your configuration file in a non-confidential issue, it is advisable to obscure key secrets; this can be done automatically by using named-checkconf -px.

If you are reporting a bug that is a potential security issue, such as an assertion failure or other crash in named, please do NOT use GitLab to report it. Instead, send mail to using our OpenPGP key to secure your message. (Information about OpenPGP and links to our key can be found at Please do not discuss the bug on any public mailing list.

For a general overview of ISC security policies, read the Knowledgebase article at

Professional support and training for BIND are available from ISC. Contact us at for more information.

To join the BIND Users mailing list, or view the archives, visit

If you're planning on making changes to the BIND 9 source code, you may also want to join the BIND Workers mailing list, at

Contributing to BIND

ISC maintains a public git repository for BIND; details can be found at

Information for BIND contributors can be found in the following files:

Patches for BIND may be submitted as merge requests on the ISC GitLab server.

By default, external contributors do not have the ability to fork BIND on the GitLab server; if you wish to contribute code to BIND, you may request permission to do so. Thereafter, you can create git branches and directly submit requests that they be reviewed and merged.

If you prefer, you may also submit code by opening a GitLab issue and including your patch as an attachment, preferably generated by git format-patch.

Building BIND 9

For information about building BIND 9, see the "Building BIND 9" section in the BIND 9 Administrator Reference Manual.

Automated testing

A system test suite can be run with make check. The system tests require you to configure a set of virtual IP addresses on your system (this allows multiple servers to run locally and communicate with each other). These IP addresses can be configured by running the command bin/tests/system/ up as root.

Some tests require Perl and the Net::DNS and/or IO::Socket::INET6 modules, and are skipped if these are not available. Some tests require Python and the dnspython module and are skipped if these are not available. See bin/tests/system/README for further details.

Unit tests are implemented using the CMocka unit testing framework. To build them, use configure --with-cmocka. Execution of tests is done by the automake parallel test driver; unit tests are also run by make check.


The BIND 9 Administrator Reference Manual (ARM) is included with the source distribution, and in .rst format, in the doc/arm directory. HTML and PDF versions are automatically generated and can be viewed at

Man pages for some of the programs in the BIND 9 distribution are also included in the BIND ARM.

Frequently (and not-so-frequently) asked questions and their answers can be found in the ISC Knowledgebase at

Additional information on various subjects can be found in other README files throughout the source tree.

Change log

A detailed list of all changes that have been made throughout the development of BIND 9 is included in the file CHANGES, with the most recent changes listed first. Change notes include tags indicating the category of the change that was made; these categories are:

Category Description
[func] New feature
[bug] General bug fix
[security] Fix for a significant security flaw
[experimental] Used for new features when the syntax or other aspects of the design are still in flux and may change
[port] Portability enhancement
[maint] Updates to built-in data such as root server addresses and keys
[tuning] Changes to built-in configuration defaults and constants to improve performance
[performance] Other changes to improve server performance
[protocol] Updates to the DNS protocol such as new RR types
[test] Changes to the automatic tests, not affecting server functionality
[cleanup] Minor corrections and refactoring
[doc] Documentation
[contrib] Changes to the contributed tools and libraries in the 'contrib' subdirectory
[placeholder] Used in the main development branch to reserve change numbers for use in other branches, e.g., when fixing a bug that only exists in older releases

In general, [func] and [experimental] tags only appear in new-feature releases (i.e., those with version numbers ending in zero). Some new functionality may be backported to older releases on a case-by-case basis. All other change types may be applied to all currently supported releases.

Bug report identifiers

Most notes in the CHANGES file include a reference to a bug report or issue number. Prior to 2018, these were usually of the form [RT #NNN] and referred to entries in the "bind9-bugs" RT database, which was not open to the public. More recent entries use the form [GL #NNN] or, less often, [GL !NNN], which, respectively, refer to issues or merge requests in the GitLab database. Most of these are publicly readable, unless they include information which is confidential or security-sensitive.

To look up a GitLab issue by its number, use the URL To look up a merge request, use

In rare cases, an issue or merge request number may be followed with the letter "P". This indicates that the information is in the private ISC GitLab instance, which is not visible to the public.