bind

bind

alpine:edge-based dockerization of bind, the DNS server software

As the site says:

BIND 9 has evolved to be a very flexible, full-featured DNS system. Whatever your application is, BIND 9 probably has the required features. As the first, oldest, and most commonly deployed solution, there are more network engineers who are already familiar with BIND 9 than with any other system.

The source code for this image is hosted on GitHub in the backplane/conex repo.

Usage

This container image is meant to provide a very simple authoritative name server for temporary or LAN use. It is not optimized for production use on the public internet.

To use it, just mount your zone files into /config/zones/ and the container will serve them authoritatively (zone files should appear with the exact name of the zone; e.g. for the zone example.com, the file would be mounted at /config/zones/example.com; and PTR records aka "reverse dns" for 192.168.0 would be mounted at /config/zones/0.168.192.in-addr.arpa).

This works because at startup the contents of /config get copied to /etc/bind and any zone files found in /etc/bind/zones are automatically added to a container-generated file /etc/bind/zones.conf

If you want more complex config, you can put a named.conf in /config/named.conf. If the string include "/etc/bind/zones.conf"; is found in the named.conf, a zones.conf file will be built containing primary references to the files found in the zones subdirectory (meaning you can add and remove zones without having to think about adjusting the named.conf file.

Default named.conf

Here you can see the default named.conf that is included with this container image:

// online man pages:
// https://bind9.readthedocs.io/
// http://linux.die.net/man/5/named.conf
// http://linux.die.net/man/8/named

options {
    directory "/etc/bind/";
    pid-file "/var/run/named/named.pid";

    allow-query { any; };
    allow-query-cache { none; };
    allow-recursion { none; };
    allow-transfer { none; };
    listen-on { any; };
    listen-on-v6 { none; };
    notify no;
    recursion no;
    trust-anchor-telemetry no;
};
controls {};
include "/etc/bind/zones.conf";

Example

The following run command demonstrates how the container might be used:

docker run \
  --detach \
  --tty \
  --publish "53:53/udp" \
  --publish "53:53/tcp"
  --volume "$(pwd)/zones:/config/zones" \
  "backplane/bind"

Entry Point Configuration

The container entry point is configured by environment variables which can be overridden by command-line arguments. The following table documents the options and their meaning.

Command-line Argument	Environment Variable	Description	Default
--bind-dir	BIND_DIR	path of the bind configuration directory	/etc/bind
--bind-config	BIND_CONFIG	full path of the named.conf bind config file	/etc/bind/named.conf
--zone-dir	ZONE_DIR	path of a directory containing (only) zone files to automatically serve	/etc/bind/zones
--zone-config	ZONE_CONFIG	full path of the zones.conf file to generate from the files found in ZONE_DIR	/etc/bind/zones.conf
--config-dir	CONFIG_DIR	path of a directory whose contents could be copied into the BIND_DIR	/config

Entry Point Usage

The entrypoint emits the following help text when started with the -h or --help command-line arguments:

Usage: entrypoint [-h|--help] [arg [...]]

-h / --help   show this message
-d / --debug  print additional debugging messages

--bind-dir BIND_DIR        path of the bind configuration directory
                           (default: '/etc/bind')
--bind-config BIND_CONFIG  full path of the 'named.conf' bind config file
                           (default: '/etc/bind/named.conf')
--zone-dir ZONE_DIR        path of a directory containing (only) zone
                           files to automatically serve
                           (default: '/etc/bind/zones')
--zone-config ZONE_CONFIG  full path of the 'zones.conf' file to generate
                           from the files found in ZONE_DIR
                           (default: '/etc/bind/zones.conf')
--config-dir CONFIG_DIR    path of a directory whose contents could be
                           copied into the BIND_DIR
                           (default: '/config')

--                         Pass the remaining command-line arguments to
                           bind directly

Generates a zones.conf file which 'includes' all the zone files found in
the ZONE_DIR, runs named-checkconf, then starts bind