Requirements

Hardware

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

However, please note that there are some scenarios that will require 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.

CPU requirements

The server scales with processing power and also with the number of available cores/CPUs. Enabling Hyper-threading is convenient if supported.

There is no lower bound on the CPU requirements, but it should support memory barriers and atomic instructions (i586 and newer).

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).

Memory requirements

The server implementation focuses on performance and thus can be quite memory demanding. The rough estimate for memory requirements is 3 times the size of the zone in the plain-text format. Again this is only an estimate and you are advised to do your own measurements before deploying Knot DNS to production.

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.

Operating system

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

  • liburcu >= 0.5.4

  • lmdb >= 0.9.15

Note

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

Optional libraries

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

  • libidn2 (or libidn)

Systemd's startup notification mechanism and journald logging:

  • libsystemd

Dnstap support in kdig or module dnstap:

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

Linux capabilities(7) support, which allows the server to be started as a non-root user/group, binding to privileged ports (53), and giving up all its capabilities, resulting in a completely unprivileged process:

  • libcap-ng >= 0.6.4

MaxMind database for geodb support in module geoip:

  • libmaxminddb0

DNS-over-HTTPS (DoH) support in kdig:

  • libnghttp2

The XDP functionality and kxdpgun tool. These are only supported on Linux operating systems. See the chapter Mode XDP for software and hardware recommendations.

  • libbpf >= 0.0.6 (or embedded one via --enable-xdp)

  • libxdp (if libbpf >= 1.0)

  • libmnl (for kxdpgun)

DNS-over-QUIC (DoQ) support in knotd, kxdpgun, and kdig:

  • libngtcp2 >= 0.13.0 (or embedded one via --enable-quic)

  • gnutls >= 3.7.2

  • Mode XDP (for knotd and kxdpgun)