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ansible-role-bind

This Ansible role will deploy a Docker container running the ISC Bind DNS service and configure it to your liking.

The container used is jonasal/bind from here.

Installation

This repository does not have any dependencies, so just move into your roles/ folder and run the following:

git clone [email protected]:JonasAlfredsson/ansible-role-bind_dns.git bind

If you would like to download any updates for this role in the future, you may use the following command from within the previously cloned folder:

git pull

When the configuration is complete you may then just include this role in your main playbook like this:

- hosts: dns_servers
  name: Install Bind DNS server
  roles:
    - bind

Usage

Bind has a ton of configuration possibilities so it is absolutely impossible for me to create a role that covers every conceivable usecase, but I have tried to make the most common ones easy to achieve and some more advanced stuff possible by allowing freestyle text in the variables available.

I like this for reading about what options are available, but even that does not cover everything.

Example Configuration

To add some kind of structure to the example configuration I will split it into four different categories.

Container Options

The settings grouped in the Container options section have more of an impact on the host and the actual Docker container than the Bind program. One setting that probably should be changed is the base directory in which the container will find the configuration files and write its logs:

bind_container_base_dir: "/srv/bind"

Then there is the following setting:

bind_use_host_network: false

which, when set to true, make the container use the host network (and thus ignore anything listed in bind_container_networks and bind_container_ports). This will most likely be necessary in case you want to enable IPv6 support, but please read this section before you do.

Don't forget to update bind_container_command and bind_listen_on_v6 if you do enable IPv6.

Bind Logging

Logging is important, and Bind is not very good at it. By default the container is configured so that Bind tries to load its logging configuration from a file, but if anything fails during startup it will not output any information. The only way around this is then to force all log output to stderr (i.e. the console) by setting this.

bind_log_force_stderr: true

When you know everything works you may turn this off again and load the proper configuration from the named.cong.logging file. This resource is pretty good at explaining how the logging works, but important to know here is that I have defined a default "console" channel which always try to output to stderr. The severity of that one is controlled with

bind_log_channel_console_severity: "info"

and the obligatory "default" category will have this "console" channel included unless you manually change it to something else.

bind_log_category_default: [ "console" ]

Beyond that you may define your own channels and categories like this

bind_log_channels:
  "custom_channel_1":
    severity: "warning"
  "custom_channel_2":
    severity: "debug 1"
    print_time: no
    print_severity: no
    print_category: no

bind_log_categories:
  "client":
    - "custom_channel_1"
  "database":
    - "custom_channel_2"
    - "console"

Bind Options

Looking in the defaults file, and then in the named.conf.options file, it should be quite easy to see what is going on here.

Unless you try to do something very advanced you can actually get away with the options block being pretty sparse. But, as was mentioned at the beginning, there exists a ton of options here and there is no way to prepare for all of them. As a workaround for this it is possible to add some "raw" text into the options file like this.

bind_options_raw: |
  custom_option_1 yes;
  custom_option_2 {
    "list_item";
  };

The | character here allows you to write a multiline text (with empty lines!), so you just need to make sure that noting is indented less than the first line.

Bind Local

It is in this file where most of the action will take place. Here you define the controls and the zones you intend to serve. To begin with we take a look at the controls setting and how you configure it.

bind_controls

bind_controls:
  "name_of_key_1":
    inet: '*'
    port: '953'
    allow: [ 'localhost' ]
    secret: "abcdef"
  "name_of_key_2":
    secret: "ghijkl"

The name needs to be unique, which is why it is used as the key in the map above. The only thing that is required is the secrets value, and that may be created by following these steps.

bind_include_default_zones and bind_include_rfc1918

Of the following two settings you should set the rfc1918 one to false if you want your Bind instance to be able to respond with IP addresses that are in private ranges.

bind_include_default_zones: true
bind_include_rfc1918: true

bind_zones

Then we come to the largest variable in this entire role, as it allows you to configure all your zones from a single location. Any value that does not have a comment after it will default to the value written here.

bind_zones:
  "example.com":
    type: "primary"  # Required
    allow_transfer: [ "none" ]
    also_notify: []
    ttl: "1h"
    refresh: "3h"
    retry: "1h"
    expire: "1w"
    neg_cache: "1h"
    nameservers:  # Must be at least 1 long if "primary"
      - "ns0.example.com"
    rname: "admin.example.com"
    hosts:
      "192.168.0.4":
        name: "ns0"
        cnames: [ "main-computer", "main" ]
      "192.168.0.5":
        name: "www"
    custom_records:
      "MX":
        - name: ""
          data: "10 mail.example.com."
      "SRV":
        - name: "_http._tcp.example.com."
          data: "0    5      80   www.example.com."
  "upstream.com":
    type: "secondary"  # Required
    primaries:  # Must be present in case of "secondary"
      - "10.0.0.4"
    raw_options: |
      zero-no-soa-ttl yes;
      zone-statistics full;

So while I can try to explain all of these settings I think it is easier to just add the files outputted here instead so you can see how each value will be printed.

Also, read the section about rname to understand its formatting.

named.conf.local
zone "example.com" {
    type primary;
    file "/var/cache/bind/example.com/soa.conf";

    allow-transfer {
        none;
    };
};

zone "upstream.com" {
    type secondary;
    file "/var/cache/bind/db.upstream.com.secondary";
    primaries {
        10.0.0.4;
    };

    zero-no-soa-ttl yes;
    zone-statistics full;
};
example.com zonefile
$TTL 1h
$ORIGIN example.com.
@                   IN    SOA     ns0.example.com. admin.example.com. (
                          1658264049    ; serial
                          3h            ; refresh
                          1h            ; retry
                          1w            ; expire
                          1h            ; negative caching TTL
                          )
@                   IN    NS      ns0.example.com.

ns0                        IN  A      192.168.0.4
main-computer              IN  CNAME  ns0
main                       IN  CNAME  ns0
www                        IN  A      192.168.0.5

                           IN  MX      10 mail.example.com
_http._tcp.example.com.    IN  SRV     0    5      80   www.example.com.