diy dynamic dns - sync cloudflare domain name with dynamic ip address every 60 seconds

dns-ip-sync.service

[Unit]
Description=dns ip sync
Wants=network-online.target
After=network-online.target
AssertPathExists=/etc/dns-ip-sync.json

[Service]
Type=simple
ExecStartPre=curl \
  --silent \
  --location \
  --output /usr/local/bin/dns-ip-sync.sh \
  --url https://gist.githubusercontent.com/grenade/012c993e16aef34297653b71199aef33/raw/dns-ip-sync.sh?$(uuidgen)
ExecStartPre=chmod +x /usr/local/bin/dns-ip-sync.sh
ExecStart=/usr/local/bin/dns-ip-sync.sh
Restart=always
RestartSec=60

[Install]
WantedBy=multi-user.target

dns-ip-sync.sh

#!/bin/bash

dns_resolver=1.1.1.1
public_ip_url=https://checkip.amazonaws.com
ip_address_pattern="^[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+$"

cloudflare_dns_zone_id=$(jq -r .cloudflare.dns.zone.id /etc/dns-ip-sync.json)
cloudflare_dns_zone_name=$(jq -r .cloudflare.dns.zone.name /etc/dns-ip-sync.json)
cloudflare_dns_record_id=$(jq -r .cloudflare.dns.record.id /etc/dns-ip-sync.json)
cloudflare_dns_record_name=$(jq -r .cloudflare.dns.record.name /etc/dns-ip-sync.json)
cloudflare_api_token=$(jq -r .cloudflare.api.token /etc/dns-ip-sync.json)

observed_public_ip=$(curl -s -X GET ${public_ip_url})

if [[ ! ${observed_public_ip} =~ ${ip_address_pattern} ]]; then
  echo "failed to observe public ip address at: ${public_ip_url}"
  unset observed_public_ip
  exit 1
else
  echo "public ip address observed as: ${observed_public_ip}, at: ${public_ip_url}"
  if host ${cloudflare_dns_record_name} ${dns_resolver} | grep 'has address' | grep ${observed_public_ip}; then
    echo "${cloudflare_dns_record_name} resolves to ${observed_public_ip}"
    exit
  else
    if [ -z ${cloudflare_dns_zone_id+x} ]; then
      cloudflare_dns_zone_id=$(curl \
        --silent \
        --request GET \
        --header "Content-Type: application/json" \
        --header "Authorization: Bearer ${cloudflare_api_token}" \
        --url "https://api.cloudflare.com/client/v4/zones?name=${cloudflare_dns_zone_name}&status=active" \
        | jq -r '.result[0].id')
    fi
    if [ -z ${cloudflare_dns_zone_id+x} ]; then
      echo "failed to obtain cloudflare dns zone id for zone: ${cloudflare_dns_zone_name}"
      exit 1
    fi
    if [ -z ${cloudflare_dns_record_id+x} ]; then
      cloudflare_dns_record_id=$(curl \
        --silent \
        --request GET \
        --header "Content-Type: application/json" \
        --header "Authorization: Bearer ${cloudflare_api_token}" \
        --url "https://api.cloudflare.com/client/v4/zones/${cloudflare_dns_zone_id}/dns_records?type=A&name=${cloudflare_dns_record_name}" \
        | jq -r '.result[0].id')
    fi
    if [ -z ${cloudflare_dns_record_id+x} ]; then
      echo "failed to obtain cloudflare dns record id for record: ${cloudflare_dns_record_name}, in zone: ${cloudflare_dns_zone_name} (${cloudflare_dns_zone_id})"
      exit 1
    fi
    if curl \
      --silent \
      --request PUT \
      --header "Content-Type: application/json" \
      --header "Authorization: Bearer ${cloudflare_api_token}" \
      --data "{\"type\":\"A\",\"name\":\"${cloudflare_dns_record_name}\",\"content\":\"${observed_public_ip}\",\"ttl\":1,\"proxied\":false}" \
      --url "https://api.cloudflare.com/client/v4/zones/${cloudflare_dns_zone_id}/dns_records/${cloudflare_dns_record_id}"; then
      echo "${cloudflare_dns_record_name} A record set to ${observed_public_ip} in zone: ${cloudflare_dns_zone_name} (${cloudflare_dns_zone_id}), record: ${cloudflare_dns_record_name} (${cloudflare_dns_record_id})"
    fi
  fi
fi

install

• prerequisites

  # fedora
  sudo dnf install curl jq
  
  # ubuntu
  sudo apt install curl jq

• download systemd unit file

  sudo curl -sL \
    -o /etc/systemd/system/dns-ip-sync.service \
    https://gist.githubusercontent.com/grenade/012c993e16aef34297653b71199aef33/raw/dns-ip-sync.service

• insert secrets and configuration

  # set cloudflare_api_token
  cloudflare_api_token=secret
  sudo sed -i "s/f6c29d04b0ae425293f855831d12ff12/${cloudflare_api_token}/" /etc/systemd/system/dns-ip-sync.service
  
  # set cloudflare_dns_record
  cloudflare_dns_record=office.bananas.com
  sudo sed -i "s/home.example.com/${cloudflare_dns_record}/" /etc/systemd/system/dns-ip-sync.service
  
  # set cloudflare_dns_zone
  cloudflare_dns_zone=bananas.com
  sudo sed -i "s/example.com/${cloudflare_dns_zone}/" /etc/systemd/system/dns-ip-sync.service

• enable and start service

  sudo systemctl enable --now dns-ip-sync.service

• tail service logs

  journalctl -u dns-ip-sync.service -f