User:Matthews/Drafts/Knot Resolver

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Knot Resolver is a minimalistic implementation of a caching validating DNS resolver.

Installation

USE flags

USE flags for net-dns/knot-resolver A scaleable caching DNS resolver

+manager	Manager is a user-friendly interface and a component handling rolling restarts, config update logic and more.
caps	Use Linux capabilities library to control privilege
debug	Enable extra debug codepaths, like asserts and extra output. If you want to get meaningful backtraces see https://wiki.gentoo.org/wiki/Project:Quality_Assurance/Backtraces
dnstap	Build dnstap binary logging module
jemalloc	Use dev-libs/jemalloc for memory management
kresc	Build (experimental) command-line client
nghttp2	DNS-over-HTTPS support
prometheus	Metrics exported in Prometheus
systemd	Enable use of systemd-specific libraries and features like socket activation or session tracking
test	Enable dependencies and/or preparations necessary to run tests (usually controlled by FEATURES=test but can be toggled independently)
verify-sig	Verify upstream signatures on distfiles
xdp	Enable eXpress Data Path

Data provided by the Gentoo Package Database · Last update: 2024-12-05 12:28 More information about USE flags

Emerge

root #emerge --ask net-dns/knot-resolver

Configuration

The Knot Resolver configuration is handled via a Lua script, /etc/knot-resolver/kresd.conf. It defaults to listening on localhost and acting as a recursive resolver.

Moving cache to tmpfs

To improve performance and reduce disk I/O, the resolver cache can be moved to a tmpfs by mounting one at /var/cache/knot-resolver:

FILE /etc/fstab

tmpfs        /var/cache/knot-resolver        tmpfs   rw,size=2G,uid=knot-resolver,gid=knot-resolver,nosuid,nodev,noexec,mode=0700 0 0

The cache.fssize() function can be used in the configuration, to make the cache module aware of the tmpfs size:

FILE /etc/knot-resolver/kresd.conf

cache.size = cache.fssize() - 10*MB

Adding to runlevel

OpenRC

OpenRC users can add the kresd init script to the default runlevel with the following command:

root #rc-update add kresd default

systemd

The kresd systemd unit is templated, allowing multiple instances to be created for high availability and to handle higher volumes of traffic. For maximum performance, it is recommended to create as many instances as there are CPUs.

To start a single instance:

root #systemctl enable --now kresd@1.service

To start four instances:

root #systemctl enable --now kresd@{1..4}.service

See also

• BIND — a popular free software DNS server