# Knot DNS Resolver

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The Knot DNS Resolver is a caching full resolver implementation written in C and [LuaJIT][luajit], both a resolver library and a daemon. The core architecture is tiny and efficient, and provides a foundation and
a state-machine like API for extensions. There are three of those built-in - *iterator*, *cache*, *validator*, and most of the [rich features](https://knot-resolver.readthedocs.io/en/latest/modules.html) are written in LuaJIT, Go and C. Batteries are included, but optional. 

The LuaJIT modules, support for DNS privacy and DNSSEC, and persistent cache with low memory footprint make it a great personal DNS resolver or a research tool to tap into DNS data. TL;DR it's the [OpenResty][openresty] of DNS.

Several cache backends (LMDB, Redis and Memcached), strong filtering rules, and auto-configuration with etcd make it a great large-scale resolver solution. 

The server adopts a [different scaling strategy][scaling] than the rest of the DNS recursors - no threading, shared-nothing architecture (except MVCC cache that may be shared) that allows you to pin instances on available CPU cores and grow by self-replication. You can start and stop additional nodes depending on the contention without downtime.

It also has strong support for DNS over TCP, notably TCP Fast-Open, query pipelining and deduplication, and response reordering.

### Packages

Knot Resolver is packaged for Debian, Fedora, Ubuntu and [openSUSE](https://build.opensuse.org/package/show/server:dns/knot-resolver).
See [project page](https://www.knot-resolver.cz/pages/try.html) for more information.

### Building from sources

The Knot DNS Resolver [depends][depends] on the 2.1 version of the Knot DNS library, [LuaJIT][luajit] and [libuv][libuv].
See the [Building project][depends] documentation page for more information.

### Docker image

This is simple and doesn't require any dependencies or system modifications, just run:

```
$ docker run -it cznic/knot-resolver
```

See the build page [hub.docker.com/r/cznic/knot-resolver](https://hub.docker.com/r/cznic/knot-resolver/) for more information and options.

### Running

The project builds a resolver library in the `lib` directory, and a daemon in the `daemon` directory. It requires no configuration or parameters to run a server on localhost.

```
$ kresd
```

See the documentation at [knot-resolver.readthedocs.io][doc] for more options.

[depends]: https://knot-resolver.readthedocs.io/en/latest/build.html
[doc]: https://knot-resolver.readthedocs.io/en/latest/index.html
[scaling]: https://knot-resolver.readthedocs.io/en/latest/daemon.html#scaling-out
[deckard]: https://gitlab.labs.nic.cz/knot/deckard
[luajit]: http://luajit.org/
[libuv]: https://github.com/libuv/libuv
[openresty]: https://openresty.org/

### Contacting us

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