Programming

I wanted to be able to configure a DNS hostname dynamically, but couldn’t find an easy-to-use dynamic DNS client that suited my needs. Using Ansible and Amazon Route53, I put together a quick, effective solution.

Requirements

First, you need an AWS account with a Route53 DNS zone. I followed these directions to create a subdomain.

Next, you need a remote host that accessible via SSH. On that host, install Python and the Boto library. Make sure that Boto is configured with sufficient AWS credentials to access and change your Route53 zone.

Ansible Configuration

This section was updated on 2016-11-29 to reflect improvements I’ve made in the Ansible playbook.

Ansible made this task simple. In fact, the playbook below is mostly based on example recipes from the Ansible Route53 module documentation. The YAML playbook should look like the example below. Replace YOUR-ROUTE53-ZONE with the zone you configured in Route53. Replace YOUR-FULL-DYNAMIC-HOSTNAME with the fully-qualified domain name that you’ll use for dynamic DNS.

Note that this uses the ipify_facts Ansible module. You can use the default value or pass api_url like I’m doing in this example.

---
- name: Update Dynamic IP
  hosts: localhost
  vars:
    dyn_zone: YOUR-ROUTE53-ZONE
    dyn_hostname: YOUR-FULL-DYNAMIC-HOSTNAME
  tasks:
    - name: Get public IP
      ipify_facts: api_url=https://arnesonium.com/api/yourip.php
      connection: local
    - name: Get existing host information
      register: dynip
      route53:
        command: get
        zone: "{{ dyn_zone }}"
        record: "{{ dyn_hostname }}"
        type: A
    - name: Delete existing host information
      when: ipify_public_ip != dynip.set.value
      route53:
        command: delete
        zone: "{{ dyn_zone }}"
        record: "{{ dynip.set.record }}"
        ttl: "{{ dynip.set.ttl }}"
        type: "{{ dynip.set.type }}"
        value: "{{ dynip.set.value }}"
    - name: Create new host record
      when: ipify_public_ip != dynip.set.value
      route53:
        command: create
        zone: "{{ dyn_zone }}"
        record: "{{ dyn_hostname }}"
        type: A
        ttl: 600
        value: "{{ ipify_public_ip }}"

Running Your Playbook

I named my playbook dyndns.yml, so I run it with this shell command:

ansible-playbook -vv dyndns.yml

The -vv increases the verbosity so you can see what’s going on.

The Next Step

Next, I need to convince this script to run every time my laptop’s network comes back online. I’m sure there’s a good way to do that, but I haven’t spent much time looking into it.

Did this playbook work for you? Let me know! I’d love to get feedback on it.