Updates DNS entry on Cloudflare

cloudflare_ddns.md

cloudflare_ddns

Script to automatically update A DNS entry on Cloudflare

Requirements

curl and jq must be installed.

Setup

• Grab an API key from here.
  • "Create Token"
  • "Edit zone DNS" - "Use template"
  • Give your token a descriptive name
  • "Zone Resources" - "Include" - "Specific zone" - select the target zone to modify
  • "Continue to summary"
  • "Create Token"
  • Paste the newly-created token in the token variable
• Set the other variables accordingly
• Run the script
• (optional) Set up a crontab entry so it runs every once in a while.

cloudflare_ddns.sh

#!/bin/bash

# Define variables here
target_domain="example.com"
target_subdomain="subdomain"
token="T-1234567891011121314151617181920"

# Fetches and saves public IP to $public_ip_address
function fetch_public_ip() {
    # Get public IP (in IPv4 specification)
    public_ip_address=$(curl -s http://ipv4.icanhazip.com/)
}

# Fetches and saves target zone ID to $target_zone_id
function fetch_target_zone_id() {
    target_zone_id=$(curl -s -X GET "https://api.cloudflare.com/client/v4/zones" \
    -H "Authorization: Bearer $token" \
    -H "Content-Type: application/json" | jq -r --arg domain $target_domain '.result[] | select(.name == $domain).id')
}

# Fetches and saves target DNS record ID to $target_dns_record_id
function fetch_target_dns_record_id() {
    target_dns_record_id=$(curl -s -X GET "https://api.cloudflare.com/client/v4/zones/$target_zone_id/dns_records" \
    -H "Authorization: Bearer $token" \
    -H "Content-Type: application/json" | jq -r --arg name "$target_subdomain.$target_domain" '.result[] | select(.name == $name).id')
}

# Updates DNS entry on Cloudflare
function update_cloudflare_dns_entry() {
    curl -s -X PUT "https://api.cloudflare.com/client/v4/zones/$target_zone_id/dns_records/$target_dns_record_id" \
     -H "Authorization: Bearer $token" \
     -H "Content-Type: application/json" \
     --data '{"type":"A","name":"'"$target_subdomain.$target_domain"'","content":"'"$public_ip_address"'","ttl":60,"proxied":false}'
}

function main() {
    echo "Starting on $(date)..."
    
    fetch_public_ip
    echo "Your public IP is $public_ip_address."
    
    fetch_target_zone_id
    echo "The target zone ID is $target_zone_id."
    
    fetch_target_dns_record_id
    echo "The target DNS record ID is $target_dns_record_id."
    
    update_cloudflare_dns_entry
}

main