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.. highlight:: none
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.. _Requirements:
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************
Requirements
************

Hardware
========
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Knot DNS requirements are not very demanding for typical
installations, and a commodity server or a virtual solution will be
sufficient in most cases.

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However, please note that there are some scenarios that will require
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administrator's attention and some testing of exact requirements before
deploying Knot DNS to a production environment. These cases include
deployment for a large number of zones (DNS hosting), large number
of records in one or more zones (TLD), or large number of requests.
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CPU requirements
----------------

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The server scales with processing power and also with the number of
available cores/CPUs. Enabling Hyper-threading is convenient if supported.
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There is no lower bound on the CPU requirements, but it should support
memory barriers and CAS (i586 and newer).

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Network card
------------

The best results have been achieved with multi-queue network cards. The
number of multi-queues should equal the total number of CPU cores (with
Hyper-threading enabled).

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Memory requirements
-------------------

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The server implementation focuses on performance and thus can be quite
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memory demanding. The rough estimate for memory requirements is
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3 times the size of the zone in the text format. Again this is only
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an estimate and you are advised to do your own measurements before
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deploying Knot DNS to production.
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.. NOTE::
   To ensure uninterrupted serving of the zone, Knot DNS
   employs the Read-Copy-Update mechanism instead of locking and thus
   requires twice the amount of memory for the duration of incoming
   transfers.
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Operating system
================
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Knot DNS itself is written in a portable way and can be compiled
and run on most UNIX-like systems, such as Linux, \*BSD, and macOS.

Required libraries
==================

Knot DNS requires a few libraries to be available:

* libedit
* GnuTLS >= 3.3
* Userspace RCU >= 0.5.4
* lmdb >= 0.9.15

.. NOTE::
   The LMDB library is included with the Knot DNS source code, however linking
   with the system library is preferred.

Optional libraries
==================

International Domain Names support (IDNA2003 or IDNA2008) in kdig:

* libidn or libidn2

Systemd's startup notifications mechanism and journald logging:

* libsystemd

Dnstap support in kdig and module dnstap:

* fstrm (and protobuf-c if building from the source code)

POSIX 1003.1e :manpage:`capabilites(7)` by sandboxing the exposed threads.
Most rights are stripped from the exposed threads for security reasons.

* libcap-ng >= 0.6.4