Updating BIND DNS records using Ansible

This is a follow up to the post. Configure BIND to support DDNS updates Now, that I’m able to dynamically update DNS records, this is where Ansible comes in. Ansible is hands down my favorite orchestration/automation tool. So I choose to use it to update my local DNS records going forward.

I’ll be using the community.general.nsupdate module.

I constructed my DNS records on my nameserver’s corresponding Ansible group_vars using the following structure:

all_dns_records:
  - zone: DNS-NAME
    records:
      - record: (@ for $ORIGIN or normal record name )
        ttl: TTL-VALUE
        state: (present or absent)
        type: DNS-TYPE
        value: VALUE-OF-DNS-RECORD

Example

---
all_dns_records:
  - zone: "rubyninja.org"
    records:
      - record: "@"
        ttl: "10800"
        state: "present"
        type: "A"
        value: "192.168.1.63"
      - record: "shit"
        ttl: "10800"
        state: "present"
        type: "A"
        value: "192.168.1.64"
  - zone: "alpha.org"
    records:
      - record: "@"
        ttl: "10800"
        state: "present"
        type: "A"
        value: "192.168.1.63"
      - record: "test"
        ttl: "10800"
        state: "present"
        type: "A"
        value: "192.168.1.64"
[...]

Deployment Ansible playbook:

---
- hosts: ns1.rubyninja.org
  pre_tasks:
    - name: Get algorithm from vault
      ansible.builtin.set_fact:
        vault_algorithm: "{{ lookup('community.general.hashi_vault', 'secret/systems/bind:algorithm') }}"
      delegate_to: localhost

    - name: Get rndckey from vault
      ansible.builtin.set_fact:
        vault_rndckey: "{{ lookup('community.general.hashi_vault', 'secret/systems/bind:rndckey') }}"
      delegate_to: localhost

  tasks:
    - name: Sync $ORIGIN records"
      community.general.nsupdate:
        key_name: "rndckey"
        key_secret: "{{ vault_rndckey }}"
        key_algorithm: "{{ vault_algorithm }}"
        server: "ns1.rubyninja.org"
        port: "53"
        protocol: "tcp"
        ttl: "{{ item.1.ttl }}"
        record: "{{ item.0.zone }}."
        state: "{{ item.1.state }}"
        type: "{{ item.1.type }}"
        value: "{{ item.1.value }}"
      when: item.1.record == "@"
      with_subelements:
        - "{{ all_dns_records }}"
        - records
      notify: Sync zone files
      delegate_to: localhost

    - name: Sync DNS records"
      community.general.nsupdate:
        key_name: "rndckey"
        key_secret: "{{ vault_rndckey }}"
        key_algorithm: "{{ vault_algorithm }}"
        server: "ns1.rubyninja.org"
        port: "53"
        protocol: "tcp"
        zone: "{{ item.0.zone }}"
        ttl: "{{ item.1.ttl }}"
        record: "{{ item.1.record }}"
        state: "{{ item.1.state }}"
        type: "{{ item.1.type }}"
        value: "{{ item.1.value }}"
      when: item.1.record != "@"
      with_subelements:
        - "{{ all_dns_records }}"
        - records
      notify: Sync zone files
      delegate_to: localhost

  post_tasks:
    - name: Check master config
      command: named-checkconf /var/named/chroot/etc/named.conf
      delegate_to: ns1.rubyninja.org
      changed_when: false

    - name: Check zone config
      command: "named-checkzone {{ item }} /var/named/chroot/etc/zones/db.{{ item }}"
      with_items:
        - "{{ all_dns_records | map(attribute='zone') | list }}"
      delegate_to: ns1.rubyninja.org
      changed_when: false

  handlers:
    - name: Sync zone files
      command: rndc -c /var/named/chroot/etc/rndc.conf sync -clean
      delegate_to: ns1.rubyninja.org

My DNS deployment a playbook breakdown:

1. Grabs the Dynamic DNS update keys from HashiCorp Vault
2. Syncs all of @ $ORIGIN records for all zones.
3. Syncs all of the records.
4. For good measure, but not necessary: Checks named.conf file.
5. For good measure, but not necessary: Checks each individual zone file.
6. Force dynamic changes to be applied to disk.

Given that in my environment I have roughly a couple of dozen DNS records, the structured for DNS records works in my environment. Thus said, my group_vars file with all my DNS records is almost 600 lines long. The playbook executing run takes around 1-2 minutes to complete. If I were to be in an environment where I had thousands of DNS records, the approached that I described here might not be the most efficient.

Tags: [ ansible bind ]

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