Simple dynamic DNS update script for a domain in DirectAdmin

directadmin-dynamic-dns.sh

#!/bin/bash

# Script for automatically updating the DNS records using the DirectAdmin API.
# Requires you to have curl, dig and json installed.
#
# By Daniël van de Giessen, 2018-09-10
# https://www.dvdgiessen.nl

# Configuration
DOMAINNAME="example.com"
DA_URL="https://directadmin.example.com:2222"
DA_USERNAME="example"
DA_PASSWORD="create_a_login_key_in_direct_admin_and_give_it_access_to_only_CMD_API_DNS_CONTROL"

# Get the currently configured IP address from the authoritive nameserver
CONFIGURED_IP="$(dig +short "${DOMAINNAME}" A @$(dig +short "${DOMAINNAME}" NS | head -n1))"

# Get current external IP address of this machine
CURRENT_IP="$(dig +short myip.opendns.com @resolver1.opendns.com)"

# Check if the IP needs to be updated
if [[ "${CONFIGURED_IP}" != "${CURRENT_IP}" ]] ; then
    # Change the IP through the DA API
    # Note: Used --insecure because our DA instance doesn't return the complete intermediate certificate.
    # If yours does, it is probably a good idea to remove the --insecure flag
    # Browsers deal with this fine since they have the intermediate in their store. curl does not.
    RESULT="$(curl -sS --insecure -u "${DA_USERNAME}:${DA_PASSWORD}" "${DA_URL}/CMD_API_DNS_CONTROL?domain=${DOMAINNAME}&action=edit&arecs0=name%3D${DOMAINNAME}.%26value%3D${CONFIGURED_IP}&type=A&name=${DOMAINNAME}.&value=${CURRENT_IP}&json=yes")"
    if [[ "$(echo "${RESULT}" | json success)" == "record added" ]] ; then
        echo "Updated IP address for ${DOMAINNAME} on DirectAdmin from ${CONFIGURED_IP} to ${CURRENT_IP}! :)"
    else
        echo "Failed to update IP address for ${DOMAINNAME} on DirectAdmin from ${CONFIGURED_IP} to ${CURRENT_IP}! :(" >&2
        echo "${RESULT}" >&2
    fi
fi