A bash script to update a Cloudflare DNS A record with the external IP of the source machine

cloudflare-ddns-update.sh

#!/bin/bash

# A bash script to update a Cloudflare DNS A record with the external IP of the source machine
# Used to provide DDNS service for my home
# Needs the DNS record pre-creating on Cloudflare

# Proxy - uncomment and provide details if using a proxy
#export https_proxy=http://<proxyuser>:<proxypassword>@<proxyip>:<proxyport>

# Cloudflare zone is the zone which holds the record
zone=example.com
# dnsrecord is the A record which will be updated
dnsrecord=www.example.com

## Cloudflare authentication details
## keep these private
cloudflare_auth_email=me@cloudflare.com
cloudflare_auth_key=1234567890abcdef1234567890abcdef


# Get the current external IP address
ip=$(curl -s -X GET https://checkip.amazonaws.com)

echo "Current IP is $ip"

if host $dnsrecord 1.1.1.1 | grep "has address" | grep "$ip"; then
  echo "$dnsrecord is currently set to $ip; no changes needed"
  exit
fi

# if here, the dns record needs updating

# get the zone id for the requested zone
zoneid=$(curl -s -X GET "https://api.cloudflare.com/client/v4/zones?name=$zone&status=active" \
  -H "X-Auth-Email: $cloudflare_auth_email" \
  -H "X-Auth-Key: $cloudflare_auth_key" \
  -H "Content-Type: application/json" | jq -r '{"result"}[] | .[0] | .id')

echo "Zoneid for $zone is $zoneid"

# get the dns record id
dnsrecordid=$(curl -s -X GET "https://api.cloudflare.com/client/v4/zones/$zoneid/dns_records?type=A&name=$dnsrecord" \
  -H "X-Auth-Email: $cloudflare_auth_email" \
  -H "X-Auth-Key: $cloudflare_auth_key" \
  -H "Content-Type: application/json" | jq -r '{"result"}[] | .[0] | .id')

echo "DNSrecordid for $dnsrecord is $dnsrecordid"

# update the record
curl -s -X PUT "https://api.cloudflare.com/client/v4/zones/$zoneid/dns_records/$dnsrecordid" \
  -H "X-Auth-Email: $cloudflare_auth_email" \
  -H "X-Auth-Key: $cloudflare_auth_key" \
  -H "Content-Type: application/json" \
  --data "{\"type\":\"A\",\"name\":\"$dnsrecord\",\"content\":\"$ip\",\"ttl\":1,\"proxied\":false}" | jq

Thanks, this was all I needed! ddclient was just overly complicated!

Picking up on the above, have made a few changes to fit my requirements.

• Checks for changes
• Logs each check
• Verifies if new "IP" is of correct format (to eliminate errors)
• Updates multiple entries (proxied and not)
• Logs each change

Now running a cronjob to check and update my DNS records (proxied and not) when there is an IP change, see this repo if looking for similar.
Full article can be found here.

Stripped down IPv4 version based on previous scripts. You'll need jq and curl.

#!/usr/bin/env bash
api_token=<CF token>
email=<CF account email>
zone_name=<DNS zone>
dns_record=<A record FQDN>

set -e

user_id=$(curl -s \
	-X GET "https://api.cloudflare.com/client/v4/user/tokens/verify" \
	-H "Authorization: Bearer $api_token" \
	-H "Content-Type:application/json" \
	| jq -r '{"result"}[] | .id')

zone_id=$(curl -s \
	-X GET "https://api.cloudflare.com/client/v4/zones?name=$zone_name&status=active" \
	-H "Content-Type: application/json" \
	-H "X-Auth-Email: $email" \
	-H "Authorization: Bearer $api_token" \
	| jq -r '{"result"}[] | .[0] | .id')

record_data=$(curl -s \
	-X GET "https://api.cloudflare.com/client/v4/zones/$zone_id/dns_records?type=A&name=$dns_record"  \
	-H "Content-Type: application/json" \
	-H "X-Auth-Email: $email" \
	-H "Authorization: Bearer $api_token")

record_id=$(jq -r '{"result"}[] | .[0] | .id' <<< $record_data)
cf_ip=$(jq -r '{"result"}[] | .[0] | .content' <<< $record_data)
ext_ip=$(curl -s -X GET -4 https://ifconfig.co)

if [[ $cf_ip != $ext_ip ]]; then
	result=$(curl -s \
		-X PUT "https://api.cloudflare.com/client/v4/zones/$zone_id/dns_records/$record_id" \
		-H "Content-Type: application/json" \
		-H "X-Auth-Email: $email" \
		-H "Authorization: Bearer $api_token" \
		--data "{\"type\":\"A\",\"name\":\"$dns_record\",\"content\":\"$ext_ip\",\"ttl\":1,\"proxied\":false}" \
		| jq .success)
	if [[ $result == "true" ]]; then
		echo "$dns_record updated to: $ext_ip"
		exit 0
	else
		echo "$dns_record update failed"
		exit 1
	fi
else
	echo "$dns_record already up do date"
	exit 0
fi